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  • 1.
    Abaray, Lahcen
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Development and Characterization Of Ceramic Particles Reinforced Metal Matrix Composites2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wear is a significant challenge encountered in the mining industry, affecting the durability and performance of materials. Hadfield steel has emerged as a commonly used material in this field due to its favorable properties. However, there is a persistent need to enhance its service life. Metal matrix composites (MMCs) offer a potential solution to address this issue. By reinforcingHadfield steel with ceramic particles, MMCs aim to improve the material's wear resistance and extend its operational lifespan. This study specifically investigates the potential of MMCs, reinforced with Zirconia Toughened Alumina (ZTA) particles, to enhance the performance of Hadfield steel in mining applications. Notably, ZTA particles are chosen for their exceptional wear resistance and low cost, making them an attractive reinforcement option. The mechanical behavior and properties of ZTA particle reinforced metal matrix composites (MMCs) were thoroughly investigated by conducting a comprehensive analysis. This analysis encompassed adetailed examination of the microstructure, composition, distribution, as well as the bonding between ZTA particles and the metallic matrix, along with rigorous measurements of hardness and wear resistance. The findings of the study reveal that the ZTA particle reinforced MMCs exhibit a uniform dispersion of ZTA particles throughout the composite material. This homogeneous distribution contributes to notable enhancements in the average hardness of the MMCs, surpassing that of Hadfield steel alone. However, the study did not observe a substantial enhancement in the wear resistance of the material.

  • 2.
    Abdulkareem Najm Al-Saedi, Ahmed
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Hedenfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    García, Andrea
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Kron, Anna-Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Bergström, Cornelia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Källkvist, Lova
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Analysis of Resin Impregnated Non-woven: In collaboration with Hitachi Energy2022Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    High voltage bushings are the most critical components of power transformers. A common material used in bushings is resin impregnated paper (RIP). Hitachi Energy is investigating whether this can be replaced with a new material, resin impregnated non-woven (RIN). One of the main reasons is that non-woven is less prone to absorb moisture compared to paper. Thus, for design purposes the mechanical, thermal and absorption properties of RIN have been studied and compared to RIP. The mechanical properties were tested by tensile and bending tests at room temperature and 80 ℃, showing that RIN has a lower elastic modulus and tensile strength than RIP at both temperatures. However, it was demonstrated that RIN does not retain its elongation at break and elasticity properties at elevated temperatures. The bending test showed no significant differences in flexural properties for RIN between room and high temperature. The thermal properties were studied with the transient plane source method (TPS) showing that both RIN and RIP had a higher specific heat capacity than pure epoxy. The thermal conductivity of the materials will be measured and included later. Lastly, the water absorption test was performed in order to provide information about the suitability of the materials used in bushings. For this different methods were used; water immersion andwater vapor testing. The immersion test showed that non-woven is more water resistant than paper and that the composites only absorb a small amount of water. No useful information was achieved from the water vapor test due to limited testing time. The results demonstrate the promising potential of RIN in bushings.

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  • 3.
    Abuhussain, Mohammed Awad
    et al.
    Architectural Engineering Department, College of Engineering, Najran University, Najran, Saudi Arabia.
    Ahmad, Ayaz
    Department of Civil Engineering, COMSATS University Islamabad, Abbottabad 22060, Pakistan.
    Amin, Muhammad Nasir
    Department of Civil and Environmental Engineering, College of Engineering, King Faisal University, Al-Ahsa 31982, Saudi Arabia.
    Althoey, Fadi
    Department of Civil Engineering, College of Engineering, Najran University, Najran, Saudi Arabia.
    Gamil, Yaser
    Department of Civil Engineering, School of Engineering, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor, Malaysia.
    Najeh, Taoufik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Data-driven approaches for strength prediction of alkali-activated composites2024In: Case Studies in Construction Materials, E-ISSN 2214-5095, Vol. 20, article id e02920Article in journal (Refereed)
    Abstract [en]

    Alkali-activated composites (AACs) have attracted considerable interest as a promising alternative to reduce CO2 emissions from Portland cement production and advance the decarbonisation of concrete construction. This study describes the data-driven predictive modelling to anticipate the compressive strength (CS) of AACs. Four different modelling techniques have been chosen to forecast the CS of AACs using the selected data set. The decision tree (DT), multi-layer perceptron (MLP), bagging regressor (BR), and AdaBoost regressor (AR) were employed to investigate the precision level of each model. When it comes to predicting the CS of AACs, the results show that the AR model performs better than the BR model, the MLP model, and the DT model by providing a higher value for the coefficient of determination, which is equal to 0.91, and a lower MAPE value, which is equal to 13.35%. However, the accuracy level of the BR model was very near to that of the AR model, with the R2 value suggesting a value of 0.90 and the MAPE value indicating a value of 14.43%. Moreover, the graphical user interface has also been developed for the strength prediction of alkali-activated composites, making it easy to get the required output from the selected inputs.

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  • 4. Acciaro, R.
    et al.
    Aulin, C.
    RISE, Innventia.
    Wågberg, L.
    Lindström, T.
    RISE, Innventia.
    Claesson, P.M.
    Varga, I.
    Investigation of the formation structure and release characteristics of self-assembled composite films of cellulose nanofibrils and temperature responsive microgels2011In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, no 4, p. 1369-1377Article in journal (Refereed)
  • 5.
    Adamopoulos, Stergios
    TEI Thessaly, Greece.
    Recovery and utilization of wood and rubber at the end of their lifespan to produce innovative products2014In: Development and Business Prospects in Thessaly by Symbiotic Utilization of Agricultural and Industrial Solid Waste to Produce Materials and Energy, November 24, Larissa, Greece, 2014Conference paper (Other academic)
  • 6.
    Adamopoulos, Stergios
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Foti, Dafni
    Aristotle University of Thessaloniki, Greece.
    Voulgaridis, Elias
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Manufacturing and properties of gypsum-based products with recovered wood and rubber materials2015In: BioResources, E-ISSN 1930-2126, Vol. 10, no 3, p. 5573-5585Article in journal (Refereed)
    Abstract [en]

    The experimental production of gypsum-based products (cylindrical samples, solid bricks) using different fractions of wood chips and rubber particles was studied. Recovered rubber and wood materials were mixed with gypsum and water in various proportions to fabricate gypsum-wood and gypsum-rubber cylindrical samples and standard solid bricks with six holes using appropriate molds. It was shown that to manufacture gypsum-wood and gypsum-rubber products with good mechanical strength, coarse fractions of wood and rubber should be used, but the proportion of wood or rubber should not exceed 25%. No thermal conductivity differences were found between the wood-and rubber-type of gypsum products, and particle size and material proportion had no effect. Samples with fine wood and rubber particles present at a lower proportion (25%) exhibited similar sound absorption behavior. The solid bricks had slightly higher strength when loaded at the large surface of their lateral upper side than when loaded at the small surface. The bricks provided better thermal insulation than both the extruded and pressed house bricks but lower than that of insulating bricks. The emission of volatile organic compounds out of the bricks was at an acceptable level according to regulations for construction products.

  • 7.
    Adawi, Rahim
    University of Skövde, School of Engineering Science.
    Preventing fatal effects of overworking: Product design solution2018Independent thesis Basic level (university diploma), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    “Overworking to death” is a phenomenon that has been noticeable in developing countries. The cause of death is mainly through ischemic strokes. While the victims’ occupations differed, they all shared a common characteristic, being positioned in a sedentary work, ranging from IT workers to doctors. This project’s aim was to develop a product that prevented or decreased the strokes that derived from sedentary overwork. This was mainly tackled by preventing one of the three causes of developing blood props, slowed blood flow. In order to gather rich data of the phenomenon, a qualitative study was conducted in China, during two months. By doing an extensive structured sampling, information rich data could be gathered during a short period of time. Data were derived from observations, questionnaires and an interview, which then was interpreted to customer needs and the final product specification. The final product became a trouser with an in built dynamic compression mechanic, that can compress the veins mostly during sitting activities, in order to prevent blood stasis. The compression mechanic works like the Chinese finger trap; compressing the calves while sitting and stretching the legs forward. It is made only out of polysaccharides fibres; cotton and corn.

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    PREVENTING FATAL EFFECTS OF OVERWORKING – PRODUCT DESIGN SOLUTION / Rahim_Adawi
  • 8.
    Afshar, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering.
    Size effect on mechanical properties of wood in transverse direction2022Conference paper (Refereed)
  • 9.
    Afshar, Reza
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics. Uppsala University.
    Alavyoon, Navid
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Ahlgren, A
    Swedish National Maritime and Transport Museums, the Vasa Museum, Stockholm, Sweden.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Full scale finite element modelling and analysis of the 17th-century warship vasa: A methodological approach and preliminary results2021In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 231, no 111765Article in journal (Refereed)
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  • 10.
    Ahmad, Maqsood
    et al.
    Base Engine & Materials Technology, Volvo Group, Gothenburg.
    Peng, Ru
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    König, Mathias
    Materials Technology for Basic Engine, Scania CV, Södertälje.
    Johansson, Sten
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    Bending Fatigue Behavior of Blast Cleaned Grey Cast Iron2017In: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016), 2017, Vol. 2, p. 193-198Conference paper (Refereed)
    Abstract [en]

    This paper presents a detailed study on the effect of an industrial blast cleaning process on the fatigue behavior of a grey cast iron with regard to the residual stresses and microstructural changes induced by the process. A comparison was also made to the effect of a machining operation which removed the casting skin layer. The blast cleaning process was found to greatly improve the fatigue resistance in both the low and high cycle regimes with a 75% increase in the fatigue limit. Xray diffraction measurements and scanning electron microscopic analyses showed that the improvement was mainly attributed to compressive residual stresses in a surface layer up to 800 μm in thickness in the blast cleaned specimens. The machining also gave better fatigue performance with a 30% increase in the fatigue limit, which was ascribed to the removal of the weaker casting skin layer.

  • 11.
    Ahmed, Sheikh Ali
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Hosseinpourpia, Reza
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Michigan Technological University, USA.
    Adamopoulos, Stergios
    Swedish University of Agricultural Sciences, Sweden.
    Micro-Fibrillated Cellulose in Lignin–Phenol–Formaldehyde Adhesives for Plywood Production2023In: Forests, E-ISSN 1999-4907, Vol. 14, no 11, article id 2249Article in journal (Refereed)
    Abstract [en]

    Petrochemical-based phenol–formaldehyde (PF) adhesives are widely used in plywood production. To substitute phenol in the synthesis of PF adhesives, lignin can be added due to its structural similarity to phenol. Moreover, micro-fibrillated cellulose (MFC) can further enhance the bond performance, mechanical properties, and toughness of adhesive systems. Thus, the aim of this study was to evaluate the adhesion performance of lignin–PF (LPF) adhesives reinforced with MFC. In LPF formulations, three levels of MFC (0, 15, and 30 wt% based on the total solid content of adhesives) were added to the homogenous adhesive mixture. Three-layer plywood panels from birch (Betula pendula Roth.) veneers were assembled after hot pressing at 130 °C under two pressing durations, e.g., 60 and 75 s/mm. Tensile shear strength was measured at dry (20 °C and 65% RH) and wet conditions (water soaked at room temperature for 24 h). The results indicated that the addition of lignin reduced the strength of LPF adhesives in both dry and wet conditions compared to the control PF adhesive. However, MFC reinforcement enhanced the shear strength properties of the plywood. Furthermore, a longer pressing time of 75 s/mm slightly increased the shear strength.

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  • 12.
    Ait ouakrim, Abderrahim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Microstructure and Mechanical Investigation ofCarbides Particles Reinforced High AusteniticManganese Steel2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this study was to produce a metal matrix composite (MMC). This compositematerial proves highly suitable for scenarios involving abrasive wear, owing to the exceptionalhardness of carbide particles, in conjunction with the remarkable ductility and capacity for workhardening found in Hadfield steel. Therefore, the effect of WC and TiC on the microstructure,mechanical properties, and wear resistance was investigated. The X-Ray Diffraction (XRD)technique and Scanning Electron Microscope coupled with Energy X-ray Dispersive Spectroscopy(SEM-EDS) were employed to examine the phase transformation and microstructurecharacteristics of the MMCs. The grain size of carbides was calculated using ImageJ software.The wear test was conducted using a mini jaw crusher equipped with a stationary jaw (SJ) andmovable jaw (MJ). The wear characterization involved assessing volume loss, hardness profile,and the worn surface. The microstructures showed the formation of carbides particles dispersedwithin the matrix. Compared to the hardness of the manganese steel matrix, the MMCs exhibiteda significant increase in hardness. Regarding the wear performances, the movable jaw (MJ)demonstrated greater resistance (lower volume loss) compared to the stationnary jaw (SJ), indicatingdifferent wear mechanisms between the two jaws. The worn surface exhibited a texturedappearance with visible grooves, scratches, and embedded abrasive fragments. The hardnessprofile from the worn surface towards the core displayed a gradual decrease for both the SJ andMJ, indicating the work hardening capacity of manganese steel.

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  • 13.
    Aitomäki, Yvonne
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Westin, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. University of Jyvaskyla, Department of Physics.
    Korpimäki, Jani
    CSI Composites.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanofibre distribution in composites manufactured with epoxy reinforced with nanofibrillated cellulose: model prediction and verification2016In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 139, article id 012011Article in journal (Refereed)
    Abstract [en]

    In this study a model based on simple scattering is developed and used to predict the distribution of nanofibrillated cellulose in composites manufactured by resin transfer moulding (RTM) where the resin contains nanofibres. The model is a Monte Carlo based simulation where nanofibres are randomly chosen from probability density functions for length, diameter and orientation. Their movements are then tracked as they advance through a random arrangement of fibres in defined fibre bundles. The results of the model show that the fabric filters the nanofibres within the first 20 µm unless clear inter-bundle channels are available. The volume fraction of the fabric fibres, flow velocity and size of nanofibre influence this to some extent. To verify the model, an epoxy with 0.5 wt.% Kraft Birch nanofibres was made through a solvent exchange route and stained with a colouring agent. This was infused into a glass fibre fabric using an RTM process. The experimental results confirmed the filtering of the nanofibres by the fibre bundles and their penetration in the fabric via the inter-bundle channels. Hence, the model is a useful tool for visualising the distribution of the nanofibres in composites in this manufacturing process.

  • 14.
    Akbari, Saeed
    et al.
    RISE Research Institutes of Sweden, Digital Systems, Smart Hardware.
    Sakhaei, A. H.
    University of Kent, UK.
    Panjwani, S.
    Singapore University of Technology and Design, Singapore.
    Kowsari, K.
    Singapore University of Technology and Design, Singapore.
    Ge, Q.
    Southern University of Science and Technology, China.
    Shape memory alloy based 3D printed composite actuators with variable stiffness and large reversible deformation2021In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 321, article id 112598Article in journal (Refereed)
    Abstract [en]

    Soft composite actuators can be fabricated by embedding shape memory alloy (SMA) wires into soft polymer matrices. Shape retention and recovery of these actuators are typically achieved by incorporating shape memory polymer segments into the actuator structure. However, this requires complex manufacturing processes. This work uses multimaterial 3D printing to fabricate composite actuators with variable stiffness capable of shape retention and recovery. The hinges of the bending actuators presented here are printed from a soft elastomeric layer as well as a rigid shape memory polymer (SMP) layer. The SMA wires are embedded eccentrically over the entire length of the printed structure to provide the actuation bending force, while the resistive wires are embedded into the SMP layer of the hinges to change the temperature and the bending stiffness of the actuator hinges via Joule heating. The temperature of the embedded SMA wire and the printed SMP segments is changed sequentially to accomplish a large bending deformation, retention of the deformed shape, and recovery of the original shape, without applying any external mechanical force. The SMP layer thickness was varied to investigate its effect on shape retention and recovery. A nonlinear finite element model was used to predict the deformation of the actuators. 

  • 15.
    Akbarpour, Sahar
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures. KTH.
    Enhanced Composite Joint Performance through Interlacement of Metal Inserts2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work in this thesis investigates bolted joints in fibre reinforced composites with particular focus on a novel insert concept. The concept is characterised by replacing all composite plies with stacked metal patches, locally around a bolt hole, so that they jointly form a solid metal reinforcement. An extensive experimental study is presented together with finite element analysis of the studied cases.

    Reinforcing bolt holes with high-strength metals improves the bearing load capacity of the composite laminates. True enhancement of the joint performance however requires that the open-hole tensile strength is improved as well. The work started with tests of pin-loaded and open-hole tensile specimens with inserts, and significant improvement of the bearing load capacity was found. The initial tests enabled more informed design, and insert configurations having sufficient open-hole tensile strength could thereby be manufactured and tested. In parallel, composite-metal joints were numerically modelled to simulate and analyse the mechanical performance of the joints and gain a better understanding of the governing damage mechanisms.

    The performance of the joints was eventually investigated by means of experiments on single-shear, single- and double-bolt specimens, with and without inserts. The allowable bolt distance and the influence from the bolt tightening torque were also examined.

    The initial samples had inserts of stainless steel. Later, specimens with titanium alloy inserts were also included in the test series. Various insert configurations were designed to study the effects of different features in the composite-metal bond lines. The numerical simulations of the composite--metal interfaces were performed with two types of models, one joining the two materials directly to each other, without modelling any adhesive film in between, and the other including an elastic representation of the adhesive layer. The experimental results were then used to support verification of the results from the simulations.

    The final assessment of the concept was performed on insert configurations designed either for pure tensile loading or for more general (bi-directional) loading conditions, and the bearing load capacity, open-hole tensile strength and the performance of bolted joints were compared for cases with different inserts. While higher bearing strength improvement was achieved when the holes were reinforced with inserts of stainless steel, reinforcement with inserts of titanium was even more successful since it improved virtually all studied aspects of the joints considerably.

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  • 16.
    Akbarpour, Sahar
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Hallström, Stefan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Enhancing the performance of bolted joints in composites by use of patched steel or titanium inserts2021In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 275, article id 114464Article in journal (Refereed)
    Abstract [en]

    A new insert concept that interlaces metal inserts into composite laminates has earlier been shown to improve the relatively poor bearing strength of holes in fibre reinforced polymer composites, and it is here further and more thoroughly investigated. The concept was invented to increase the efficiency of joints with mechanical fasteners in composite materials and this work presents experiments on double-bolt joints with inserts made of either stainless steel or a titanium (Ti) alloy. In particular the work compares different implementations of the insert concept by reinforcing one or two holes in double bolt joints, and the effect of using different metals in the inserts. Some complementary tests on pin-loaded specimens and open hole tensile specimens are also performed and compared, partly with results that were reported previously. Considerable improvements of the bearing load capacity are attained, i.e. 50%-60% for steel and 35%-45% for Ti, compared to references. The open-hole tensile strength is also improved considerably (almost 30%) when the holes are reinforced with Ti inserts. The fact that the inserts can improve not only the bearing strength but also the performance in open-hole tension implies that the Ti inserts bring nothing but positive effects to the strength of the joints. The test results from single-shear double-bolt specimens with inserts at one hole showed improved strengths of 30% and 20% for specimens with steel and Ti inserts, respectively. Finally, an impressive strength improvement of 40-45% is achieved for single-shear double-bolt specimens having both holes reinforced with inserts of either steel or Ti.

  • 17.
    Akbarpour, Sahar
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Hallström, Stefan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Enhancing the performance of bolted joints in composites by use of patched steel or titanium inserts2021Report (Other academic)
    Abstract [en]

    A new insert concept that interlaces metal inserts into composite laminates has earlier been shown to improve the relatively poor bearing strength of holes in fibre reinforced polymer composites, and it is here further and more thoroughly investigated. The concept was invented to increase the efficiency of joints with mechanical fasteners in composite materials and this work presents experiments on double bolt joints with inserts made of either stainless steel or a titanium (Ti) alloy. In particular the work compares different implementations of the insert concept by reinforcing one or two holes in double bolt joints, and the effect of using different metals in the inserts. Some complementary tests on pin-loaded specimens and open hole tensile specimens are also performed and compared, also with some results reported previously.                    Considerable improvements in the bearing load capacity, i.e. 50%-60% or 35%-45%, is attained. The open-hole tensile strength is also improved considerably (almost 30%)  when the holes are reinforced with Ti inserts. The fact that the inserts can improve not only the bearing strength but also the performance in open-hole tension implies that the Ti inserts bring nothing but positive effects to the strength of the joints. The test results from single-shear double-bolt specimens with inserts at one hole showed improved strengths of 30% and 20% for specimens with steel and Ti inserts, respectively. Finally, an impressive strength improvement of 40-45% is achieved for single-shear double-bolt specimens having both holes reinforced with inserts of either steel or Ti.

  • 18.
    Akbarpour, Sahar
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Hallström, Stefan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Experimental investigation and numerical analysis of multi-material interfaces related to a composite joint concept2021Report (Other academic)
    Abstract [en]

    An insert concept for reinforcing bolt-holes with high strength metals was previously introduced by the authors, where inserts are anchored in composite laminates through interlacement of composite plies and thin metal patches. The resulting finger-joints must be strong enough to avoid composite-metal debonding happening before bearing failure at the bolt-hole. The strength of the composite-metal interfaces is thus crucial for successful implementation of the insert concept. The paper presents an experimental study investigating the strength of various interface geometries between a prepreg composite material and stainless steel or titanium alloy inserts. In addition to the experimental work, finite element simulations are performed to analyse the stresses at the interfaces. The results indicate that the stress concentrations at multi-material corner points govern the failure and that the strength can be enhanced by expedient design.

  • 19.
    Akbarpour, Sahar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Hallström, Stefan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Reinforcement around holes in composite materials by use of patched metal inserts2019In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 225, article id 111084Article in journal (Refereed)
    Abstract [en]

    Metal inserts are sometimes used to improve the load carrying capacity of bolted joints in composite materials. In this paper a new concept is introduced where inserts are built during composite manufacturing by integrating stacked metal patches at locations where holes are to be made after consolidation. Initial tests and a parameter study enable more informed design, and specimens with improved stacked inserts are then produced and tested. The specimens with inserts show up to 60% strength improvement in pin-loaded tests. In addition to the experimental work, finite element analysis is performed to investigate the stress fields and the failure mechanisms. The model indicates that the singular stresses at the multi-material corner points are governing for the strength and give indications of the failure mechanisms. Some basic analytical estimates are also presented.

  • 20.
    Akbarpour, Sahar
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Hallström, Stefan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Lightweight Structures.
    Strength improvement of bolted joints in composite materials by use of patched metal inserts2020In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 52, article id 112628Article in journal (Refereed)
    Abstract [en]

    Metal inserts are occasionally used to improve bearing load capacity of bolted joints in laminated composite materials. This paper investigates a new reinforcement concept where inserts are built by locally replacing composite plies with metal patches of various diameters, surrounding the holes. The inserts are built during composite manufacturing by alternately placing the metal patches through the thickness of the laminate at locations where holes are to be drilled after consolidation. An extensive experimental study including pin‐ loaded, open–hole tensile, and single‐shear testing of bolted specimens is presented. Considerable improve- ment of the bearing strength – 50‐60% – is attained for pin‐loaded specimens with inserts, demonstrating the potential of the reinforcement concept. The open–hole tensile tests show that the by‐pass strength can be maintained or even improved with up to 20% if the inserts are properly designed. Finally, the results from the single‐shear tests of bolted joints show more than 25% improvement in strength for reinforced single‐ and double‐bolt specimens. It is possible that the inserts would maintain clamping pressure over time, which could then almost double the imrovement (47%) for bolted joints.

  • 21.
    Akintunde, Moyinoluwa
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business. Department of Microbiology, University of Ibadan, Ibadan, Nigeria.
    Adebayo-Tayo, B C
    Department of Microbiology, University of Ibadan, Ibadan, Nigeria.
    Ishola, M M
    Department of Energy and Environment, Göteborg Energi, Gothenburg, Sweden.
    Zamani, Akram
    University of Borås, Faculty of Textiles, Engineering and Business.
    Sárvári Horváth, Ilona
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bacterial Cellulose Production from agricultural Residues by two Komagataeibacter sp. Strains2022In: Bioengineered, ISSN 2165-5979, E-ISSN 2165-5987, Vol. 13, no 4, p. 10010-10025Article in journal (Refereed)
    Abstract [en]

    Agricultural residues are constantly increasing with increased farming processes, and improper disposal is detrimental to the environment. Majority of these waste residues are rich in lignocellulose, which makes them suitable substrate for bacterial fermentation in the production of valueadded products. In this study, bacterial cellulose (BC), a purer and better form of cellulose, was produced by two Komagataeibacter sp. isolated from rotten banana and kombucha drink using corncob (CC) and sugarcane bagasse (SCB) enzymatic hydrolyzate, under different fermentation conditions, that is, static, continuous, and intermittent agitation. The physicochemical and mechanical properties of the BC films were then investigated by Fourier Transformed Infrared Spectroscopy (FTIR), Thermogravimetry analysis, Field Emission Scanning Electron Microscopy (FESEM), and Dynamic mechanical analysis. Agitation gave a higher BC yield, with Komagataeibacter sp. CCUG73629 producing BC from CC with a dry weight of 1.6 g/L and 1.4 g/L under continuous and intermittent agitation, respectively, compared with that of 0.9 g/L in HS medium. While BC yield of dry weight up to 1.2 g/L was obtained from SCB by Komagataeibacter sp. CCUG73630 under continuous agitation compared to that of 0.3 g/L in HS medium. FTIR analysis showed BC bands associated with cellulose I, with high thermal stability. The FE-SEM analysis showed that BC fibers were highly ordered and densely packed. Although the BC produced by both strains showed similar physicochemical and morphological properties, the BC produced by the Komagataeibacter sp. CCUG73630 in CC under intermittent agitation had the best modulus of elasticity, 10.8 GPa and tensile strength, 70.9 MPa. [GRAPHICS]

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  • 22.
    Alagumalai, Vasudevan
    et al.
    Department of Mechanical Engineering, Saveetha School of Engineering, SIMATS, Chennai 602105, India.
    Shanmugam, Vigneshwaran
    Department of Mechanical Engineering, Saveetha School of Engineering, SIMATS, Chennai 602105, India.
    Balasubramanian, Navin Kumar
    Department of Mechanical Engineering, Saveetha School of Engineering, SIMATS, Chennai 602105, India.
    Krishnamoorthy, Yoganandam
    Department of Mechanical Engineering, ARM College of Engineering and Technology, Kanchipuram 603209, India.
    Ganesan, Velmurugan
    Department of Agricultural Engineering, Saveetha School of Engineering, SIMATS, Chennai 602105, India.
    Försth, Michael
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Sas, Gabriel
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Berto, Filippo
    Department of Mechanical Engineering, Norwegian University of Science and Technology, 13 7491 Trondheim, Norway.
    Chanda, Avishek
    Centre for Advanced Composite Materials, Department of Mechanical Engineering, The University of Auckland, Auckland 1142, New Zealand.
    Das, Oisik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
    Impact response and damage tolerance of hybrid glass/kevlar-fibre epoxy structural composites2021In: Polymers, E-ISSN 2073-4360, Vol. 13, no 16Article in journal (Refereed)
    Abstract [en]

    The present study is aimed at investigating the effect of hybridisation on Kevlar/E-Glass based epoxy composite laminate structures. Composites with 4 mm thickness and 16 layers of fibre (14 layers of E-glass centred and 2 outer layers of Kevlar) were fabricated using compression moulding technique. The fibre orientation of the Kevlar layers had 3 variations (0, 45 and 60°), whereas the E-glass fibre layers were maintained at 0° orientation. Tensile, flexural, impact (Charpy and Izod), interlaminar shear strength and ballistic impact tests were conducted. The ballistic test was performed using a gas gun with spherical hard body projectiles at the projectile velocity of 170 m/s. The pre-and post-impact velocities of the projectiles were measured using a high-speed camera. The energy absorbed by the composite laminates was further reported during the ballistic test, and a computerised tomographic scan was used to analyse the impact damage. The composites with 45° fibre orientation of Kevlar fibres showed better tensile strength, flexural strength, Charpy impact strength, and energy absorption. The energy absorbed by the composites with 45° fibre orientation was 58.68 J, which was 14% and 22% higher than the 0° and 60° oriented composites. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

  • 23.
    Albin, Lundgren
    et al.
    Halmstad University.
    Rudolf, Bengtsson
    Halmstad University.
    Fiberarmerad betong: En analys av fiberarmerat plattbärlag2021Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Fiber-reinforced concrete is a construction material that holds high promise in progressing theconstruction industry. The fibers impact on crackproperties as well as strength means there isa wide array of application areas. Still this material holds a very limited area of application asof today. One of the main reasons for this is the lack of examples and tests in new applicationareas. This work therefore aims to identify whether fiber-reinforced lattice girder elementscan compete with an element reinforced in the traditional way in any of the categories cost,work environment, strength or environmental impact. Through literature study andcalculations, we were able to see that this method of reinforcing lattice girder elements couldbe applicable at least in some of the areas. The study saw that the steel fiber came with anincrease in cost, decrease in time, bigger impact on the environment and a better workenvironment. This means that this method could be used in some specific cases where timeand work environment is of importance. We also see that further advancements in this methodcan be made if the fibers are combined with normal rebar.

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  • 24.
    Albo Zieme, Louise
    et al.
    Jönköping University, School of Engineering, JTH, Industrial Product Development, Production and Design.
    Bergstedt, Pontus
    Jönköping University, School of Engineering, JTH, Industrial Product Development, Production and Design.
    A pre-study for functional coatings evaluated on light metals to be applied on a new HPDC Mg-alloy: Investigating tribological and thermophysical properties, as-cast and coated2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Magnesium with two-thirds of the density compared to aluminium and one-quarter of steel, intrigues product developers and material scientists due to the light metal’s excellent combination of strength to weight ratio as well as their capability of being produced as a High Pressure Die Cast component compared to other ferrous or light metal alloys.

     

    However, a magnesium alloy inherits some concerning drawbacks, limiting the exploitation in structural applications and mechanical design such as automotive, heavy machinery and aerospace components. The need for a magnesium alloy that could withstand a sufficient amount of wear, temperature and corrosive environment, leads towards the investigation and evaluation of a suitable, functional coating as a solution to exploit the evident advantages a magnesium alloy exhibits. A substantial amount of research is required in order to reduce an existing knowledge gap that is the ongoing development in the search for a sufficient functional coating and adherence capability to the highly reactive substrate that is a magnesium alloy.

     

    This industrial master thesis is an early stage investigation to evaluate how the currently used aluminium substrate with an electrodeposited coating relate and compares to a heat-treated electroless deposited coating through tribological and thermophysical induced stresses. These properties are tested with proven industrial standard methods resulted in a comprehensive conclusion and discussion regarding the feasibility of applying the coating onto a commercial magnesium alloy closely related to the Mg-alloy developed by Husqvarna and thereby contributing to technological advances to the highly relevant topic within product development in materials engineering.

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    A pre-study for functional coatings evaluated on light metals to be applied on a new HPDC Mg-alloy
  • 25.
    Alfredsen, Gry
    et al.
    Norwegian Forest and Landscape Institute, Norway.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Dibdiakova, Janka
    Norwegian Forest and Landscape Institute, Norway.
    Filbakk, Tore
    Norwegian Forest and Landscape Institute, Norway.
    Bollmus, Susanne
    Georg-August-University of Göttingen, Germany.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Thermogravimetric analysis for wood decay characterisation2012In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 70, no 4, p. 527-530Article in journal (Refereed)
    Abstract [en]

    The paper focuses on the use of thermogravimetric analysis (TGA) as a fast method for estimating the change of lignocellulosic materials during fungal degradation in laboratory trials. Traditionally, evaluations of durability tests are based on mass loss. However, to gain more knowledge of the reasons for differences in durability and strength between wooden materials, information on the chemical changes is needed. Pinus sylvestris sapwood was incubated with the brown rot fungusGloeophyllum trabeum and the white rot fungus Trametes versicolor. The TGA approach used was found to be reproducible between laboratories. The TGA method did not prove useful for wood deteriorated by white rot, but the TGA showed to be a convenient tool for fast estimation of lignocellulosic components both in sound wood and wood decayed by brown rot.

  • 26.
    Alfredsson, K. Svante
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Gawandi, A. A.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Gillespie, J. W., Jr.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Carlsson, L. A.
    Department of Mechanical Engineering, Florida Atlantic University, Boca Raton, USA.
    Bogetti, T. A.
    Army Research Laboratory, Aberdeen Proving Ground, MD, USA.
    Stress analysis of axially and thermally loaded discontinuous tile core sandwich with and without adhesive filled core gaps2011In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 93, no 7, p. 1621-1630Article in journal (Refereed)
    Abstract [en]

    An analytical study is performed to investigate the stress states in an axially and thermally loaded sandwich structure with a discontinuous ceramic tile core. General and simplified models are developed to determine stresses in the constituents of the sandwich structure with and without adhesive in the gaps between adjacent tiles. A general model that allows local bending of the face sheet and a simplified model which assumes uniform through-thickness stress distribution in the face sheets are developed. It is shown that the normal stress in the face sheet decreases when the gap is filled by adhesive, although the tile stress increases. The analytical model shows that normal and shear stresses at the face/core interface can be reduced by filling the gaps between tiles. Filled gaps also elevate the axial stiffness of the structure. Model results are verified by comparison to a previously developed analytical model and finite element analysis. (C) 2011 Elsevier Ltd. All rights reserved.

  • 27.
    Alfredsson, K. Svante
    et al.
    University of Skövde, School of Technology and Society. University of Skövde, The Virtual Systems Research Centre.
    Gawandi, A. A.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Gillespie Jr., J. W.
    Center for Composite Materials, University of Delaware, Newark, USA.
    Carlsson, L. A.
    Department of Mechanical Engineering, Florida Atlantic University, Boca Raton, USA.
    Bogetti, T. A.
    Army Research Laboratory, Aberdeen Proving Ground, USA.
    Flexural analysis of discontinuous tile core sandwich structure2012In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 94, no 5, p. 1524-1532Article in journal (Refereed)
    Abstract [en]

    Three-point flexure loading of sandwich beams with a core consisting of discrete ceramic tiles (DTSS) is considered. The tile gaps may be bonded or unbonded (open gaps). The analysis utilizes a layer-wise beam theory approach. The general formulation for the displacements and stresses in the face sheets, face/core adhesive layer, and core is derived. Solutions for stresses and displacements of the beam constituents are obtained from finite element formulation based on analytical solution of the face sheet/tile unit cell. The approach is verified by comparison to stress results obtained from ordinary finite element analysis where each layer is modeled discretely. Effects of load introduction and support conditions on the effective flexural stiffness are examined. It is demonstrated that the face sheets experience substantial stress concentrations at the tile joint locations, especially if the gaps are unfilled. Analysis of beam compliance reveals sensitivity to details of load introduction and support conditions, especially when the span length becomes comparable to the tile length.

  • 28.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Linnaeus University, Linnaeus Knowledge Environments, Advanced Materials.
    Impact of the Atomic Packing Density on the Properties of Nitrogen-Rich Calcium Silicate Oxynitride Glasses2022In: Materials, E-ISSN 1996-1944, Vol. 15, no 17, article id 6054Article in journal (Refereed)
    Abstract [en]

    In this work, the impact of the atomic packing density/fractional glass compactness of Ca-Si-O-N glasses on glass transition and crystallization temperatures, glass density, microhardness, molar volume, and refractive index were examined. It was found that the atomic packing density increased with increasing the nitrogen content and decreased with increasing the Ca content in the glass network. Furthermore, density, glass transition and crystallization temperatures, and refractive index, increased with an increasing atomic packing density of the glass, while molar volume increased with decreasing atomic packing density values. The change in hardness with atomic packing density is less clear and suggests that the atomic packing density does not solely control the underlying deformation mechanism. There is indeed competition between densification (favored at low packing density values) and isochoric shear (at larger packing density). Despite that, the effects of nitrogen as a network former and Ca as a modifier are significantly independent. The obtained results indicate that the atomic packing density of the prepared samples linearly depends on many mechanical and optical properties, suggesting that the glass network and cross-linking are proportional to the ionic radius of the Ca and the nitrogen content, respectively.

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  • 29.
    Alinejadian, Navid
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Tallinn Univ Technol, Dept Mech & Ind Engn, Ehitajate Tee 5, EE-19086 Tallinn, Estonia..
    Kazemi, S. H.
    Inst Adv Studies Basic Sci, Dept Chem, Zanjan 4513766731, Iran..
    Grossberg-Kuusk, M.
    Tallinn Univ Technol, Dept Mat & Environm Technol, Ehitajate Tee 5, EE-19086 Tallinn, Estonia..
    Kollo, L.
    Odnevall, Inger
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Karolinska Inst, AIMES Ctr Advancement Integrated Med & Engn Sci, Stockholm, Sweden.;KTH Royal Inst Technol, Stockholm, Sweden.;Karolinska Inst, Dept Neurosci, SE-17177 Stockholm, Sweden..
    Prashanth, K. G.
    Tallinn Univ Technol, Dept Mech & Ind Engn, Ehitajate Tee 5, EE-19086 Tallinn, Estonia.;Austrian Acad Sci, Erich Schmid Inst Mat Sci, Jahnstr 12, A-8700 Leoben, Austria.;Vellore Inst Technol, Sch Mech Engn, CBCMT, Vellore 632014, India..
    Importance of the micro-lattice structure of selective laser melting processed Mo/Mo(x)S(x+1) composite: Corrosion studies on the electrochemical performance in aqueous solutions2022In: Materials Today Chemistry, E-ISSN 2468-5194, Vol. 26, article id 101219Article in journal (Refereed)
    Abstract [en]

    Selective laser melting (SLM) based processing of Mo-based samples is challenging due to solidification cracking. We here demonstrate that the addition of 2 wt% MoS2 to the Mo feedstock markedly improves crack mitigation of SLM-processed Mo/MoS2/Mo2S3 composite micro-lattice structures (SLM-Mo/ Mo(x)S(x+1)). Crack inhibition is suggested to be a result of Mo2S3 formation, decreased lattice strain (0.04 4%), and a decrease in accumulated residual stresses. The increased values of polarization resistance from 42.3 and 19.2 kU cm2 to 437 and 78.2 kU cm2, respectively verified the hindering effect of the composition on stress corrosion cracking (SCC) and surface oxidation cracking. However, an increased corrosion current density, from 1.22 to 10.2 mA/cm2, and cathodic Tafel constant, from 175 to 260.5 mV, confirmed the decreased polarization resistance and occurrence of different types of corrosion such as SCC and pitting. The strategy to add 2 wt% MoS2 to the Mo feedstock enables the fabrication of hightemperature micro-lattice structure components with improved corrosion resistance properties applicable in e.g., electronic, power semiconductor heat sinks, offshore-, aerospace-, defense-, or particularly novel sodium-ion energy storage applications.

  • 30.
    Alipour, Nazanin
    et al.
    KTH Royal Institute of Technology, Sweden.
    Strömberg, Emma
    KTH Royal Institute of Technology, Sweden.
    Enebro, Jonas
    RISE Research Institutes of Sweden, Built Environment, Infrastructure and concrete technology.
    Hedenqvist, Mikael
    KTH Royal Institute of Technology, Sweden.
    Release of micro- and nanoparticles from a polypropylene/clay nanocomposite, a methodology for controlled degradation and evaluation2021In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 319, article id 128761Article in journal (Refereed)
    Abstract [en]

    A methodology was developed for qualitative assessment and characterisation of particle losses from nanocomposites during service life. The methodology can be generalised to other systems where the material fragments during ageing and can be extended to quantitative analysis. A chamber was constructed for ageing of selected materials, which enabled effective collection and subsequent analysis of released particles. A combination of scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy was found to be suitable for characterising particles in terms of size, shape and content. The methodology was tested on a common nanoclay composite with polypropylene as the matrix. There was no need for physical/mechanical wear to generate particles, slow flow of air and elevated temperature led to cracking and fragmentation of the material, and subsequent release of nanocomposite particles containing embedded or protruding clay. The release of pure clay particles and polypropylene particles was also detected. Using the methodology, it was observed that even in ‘mild’ degradation conditions (pure thermo-oxidation with no wear), fillers and nanocomposite particles can be released to the environment, which is an environmental and health concern. © 2021 The Authors

  • 31.
    Al-Lami, Noor
    University West, Department of Engineering Science.
    Solid-state additive friction-stir manufacturing technology for composite manufacturing2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    An experiment study was conducted to locally improve the properties of Al6082-T6 alloy by adding hard particles reinforcement using Friction Stir Processing. Aluminum and its alloys are the most used as a substrate material in the fabrication of Aluminum surface composites because of their lightweight. Thus, aluminum alloy is widely preferred in generating surface composite that is used in sports, marine, aerospace, aircraft, automobile, electronics, railway, etc. Industry requirements ask for good-cost materials with very high properties and light weight. To meet the market requirements, this study has been conducted to investigate the development of the microhardness of Aluminum matrix composites after treating by Friction Stir Processing. From an economic perspective, it is important to enhance the property of the materials by treating the surface instead of the core of the materials. Thus, FSP consid ered in this study as a one of the green fabrication process because it can be done without fume or toxic gases during processing.

    The basic principle of the Friction Stir Process is to use a rotating tool that provides the friction between the tool and the workpiece material producing heating, to produce the wanted plastic deformation. This project aimed to fabricate composites with different reinforcements. The reinforcements used were diamond, cubic Boron Nitride and Graphene. Friction Stir Process was carried out at the tool rotating speed of 1000, 1200 and 1500 rpm and traversing speed of 2, 3 and 5 mm/s. Effects of the number of Friction Stir Process passes were investigated. The samples were all mounted, ground, polished, and analyzed by SEM and optical microscope devices. Microhardness was recorded across the Friction Stir Process region using DU-RAMIN-40 AC1 device with applied load 20, 50, 100 gf.

    It was concluded that a good refinement of the particles size can be achieved in the processed zones for all types of reinforcement. Increasing the number of stirring passes produced well distribution of reinforcement particles and reduced the agglomeration. While increasing rotation speed during processing of graphene reinforcement led to generate more heat, subsequence more agglomeration would be produced. Finally, the results showed that by incorporating diamond reinforcement using single FSP-pass increase the microhardness by about 20% while using double FSP-pass it was found that there was no significant improvement in the microhardness of the composite. A good improvement was also achieved by incorporating the cBN reinforcement where the improvement in the microhardness was also about 20% using single FSP-pass. Increasing rotating speed in FSPed GNP reinforcement leads to generate more heat which leads to more agglomeration or clustering of the reinforcement particles

  • 32.
    Al-Maqdasi, Zainab
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Development of Constituents for Multi-functional Composites Reinforced with Cellulosic Fibers2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bio-basedcomposites are being increasingly used in applications where weight saving,and environmental friendliness is as important as structural performance. Obviously, bio-based materials have their limitations regarding durability and stability of the properties,but their potential in use for advanced applications can be expanded if they were functionalized and considered beyond their structural performance.

    Multifunctionalityincomposites can be achieved by modifyingeither of the composite constituents at different levelsso that they can perform energy-associated roles besides their structural reinforcement in the system. For the fibers, this can be done at the microscale by altering theirmicrostructure during spinning process or by applying functional coatings. As for the matrix, it is usually done by incorporating additives that can impart the required characteristics to the matrix. The nano-sized additives that mightbe considered for this objective are graphene and carbon nano-tubes. A big challenge with such materials is the difficulty to reachthe dispersionstate necessary for formation ofstable network to overcome the percolation threshold for conductivity. However, once the network is formed, the composite can have improved mechanical performance together with one or more of the added functionalities such as barrier capabilities,thermal and/or electrical conductivities or electromagnetic interference ability.

    Enormous work has been done to achieve the functionality incomposites produced with special care in laboratories. However, when it comes to mass production, it is both cost and energy inefficient to use tedious,complex methods for the manufacturing. Hence there is a need to investigate the potential of using scalable and industrial-relevant techniques and materials with acceptable compromise between cost and properties.

    The work presented in this thesis is performedwithin two projects aiming to achieve functional composites based on natural and man-made cellulosic fibers suitable for industrial upscaling. Conductive Regenerated Cellulose Fibers (RCFs) were produced by coating them with copper by electroless coating process using commercial materials. On the other hand, commercial masterbatches based on Graphene Nano-Platelets (GNPs) were used to produce wood polymer composites (WPC) with added multifunctionality by melt extrusion process. The process is one of the conventional methods used inpolymerproductionand needsno modifications for processingfunctional composites. Both materials together can be used to produce hybrid functional composites.

    The incorporation of the GNP into HDPE has resulted in improvement in the mechanical propertiesof polymer as well as composite reinforced with wood fibers. Stiffness has increased to a large extent while effect on the strength was less pronounced(>100% and 18% for stiffness and strength at 15%GNP loading). The enhancement of thermal conductivityat higher graphene loadingswas also observed. Moreover, time-dependent response of the polymer has also been affected and the addition of GNP has resulted in reduced viscoplastic strains and improved creep behavior.

    The copper-coated cellulose fibers showed a significant increasein electrical conductivity(<1Ω/50mm of coated samples) and a potential in use as sensor materials. However, these results come with the cost of reduction in mechanical properties of fibers (10% and 70% for tensile stiffness and strength, respectively) due to theeffect ofchemicals involved in the process.

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  • 33.
    Al-Maqdasi, Zainab
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Multifunctionality and Durability of Cellulosic Fiber Reinforced Polymer Composites2022Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The overall objective of this thesis is to develop and evaluate cellulose-based fiber composites with added multifunctionality for advanced applications. In the strive towards sustainable societies and industries, materials as well as production processes need to be assessed against the sustainability criteria and selected accordingly. Cellulosic fibers reinforced polymer composites are being increasingly used in applications where weight saving, and environmental friendliness is as important as structural performance. Nonetheless, these materials have their limitations regarding durability and stability of the properties, but their potential in use for advanced applications can be expanded if functionalized and considered beyond their structural performance. Such multi-functionality of composites can be achieved by the coating of fibers and/or modifying the matrix with functional reinforcement, or by both of these routes combined. Coating of fibers and modifying the matrix with nano-reinforcement are two selected approaches for imparting functionality to the cellulosic fiber composites in the current study. 

    Conductive Regenerated Cellulose Fibers (RCFs) were produced by coating commercial RCFs with copper via electroless plating process. Electrical conductivity and mechanical performance were evaluated, and the coated fibers were transformed into an embedded strains sensor-like assembly that could be used as structural health monitoring system in composites structures. A noticeable degradation in the mechanical strength of fibers was realized and it was attributed to the influence of the chemicals of the final plating step of process on the chains of cellulose as well as the loss of crystalline order in the RCF. 

    In order to obtain modified matrix (nanocomposites) for multifunctional wood polymer composites (WPC), the commercial masterbatches based on Graphene Nanoplatelets (GNPs) were utilized by melt extrusion process. Effect of the processing parameters in terms of change in screw configurations and the change in composition of the constituents on the structure and mechanical performance of the nanocomposites was studied.  Results showed that there is insignificant effect of the change in the screw configuration in comparison with the effect of increasing the content of the GNPs. Stronger shear forces did not result in better dispersion of the nanoparticles. Addition of the compatibilizer, on the other hand, resulted in an adverse effect on the properties compared to the formulations where it is absent. The use of GNPs with larger aspect ratio resulted in much better improvement in the mechanical performance. Addition of the nanoparticles did not only improve mechanical performance but also resulted in increased thermal conductivity and diffusivity, especially when micro-scale reinforcement was added because of synergy between wood fibers and the GNPs. This synergy was reflected also in the significant 99% improved wear resistance and the >80% reduction in the creep strains of wood and graphene reinforced composites. 

    During the design and selection of materials, quasi-static properties are often used as a selection criterion. However, in reality structures in use are often loaded during lengthy periods of time which are followed by multiple steps of unloading/reloading, depending on the service conditions.  In such cases their time-dependent response becomes more crucial than instantaneous mechanical response. Typically, characterization of these properties requires a lot of time, but it may be significantly shortened if proper modeling and analysis are employed. The effect of addition of GNPs to the polymer and wood composites has been studied experimentally by short term creep tests. The materials showed highly nonlinear response even at very low loading stresses, but the addition of the nanoparticles resulted in a decrease in the nonlinearity and in the irreversible strains due to plasticity. Modelling approaches have been used to extract parameters from experimental data that could be used in predicting long term performance using Zapas model for viscoplasticity and Schapery’s model for nonlinear viscoelasticity. 

    Overall, the results of the performed work contribute to enriching the research field with the potential the bio-based composites have to offer in the advanced application and how nano-scale reinforcement can interact synergistically with the micro-sized fibers to improve the overall performance of WPC and under different loading scenarios.  

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  • 34.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gong, Guan
    RISE SICOMP AB, Fibervägen 2, 943 33 Öjebyn, Sweden.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mechanical Performance of PE Reinforced with Graphene Nanoplatelets (GNPs): Effect of Composition and Processing ParametersManuscript (preprint) (Other academic)
  • 35.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gong, Guan
    Rise Sicomp AB, Fibervägen 2, SE-941 26 Öjebyn, Sweden.
    Nyström, Birgitha
    Podcomp AB, Skylvägen 1, SE-943 33 Öjebyn, Sweden.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Characterization of Wood and Graphene Nanoplatelets (GNPs) Reinforced Polymer Composites2020In: Materials, E-ISSN 1996-1944, Vol. 13, no 9, article id 2089Article in journal (Refereed)
    Abstract [en]

    This paper investigates the utilization of commercial masterbatches of graphene nanoplatelets to improve the properties of neat polymer and wood fiber composites manufactured by conventional processing methods. The effect of aspect ratio of the graphene platelets (represented by the different number of layers in the nanoplatelet) on the properties of high-density polyethylene (HDPE) is discussed. The composites were characterized for their mechanical properties (tensile, flexural, impact) and physical characteristics (morphology, crystallization, and thermal stability). The effect of the addition of nanoplatelets on the thermal conductivity and diffusivity of the reinforced polymer with different contents of reinforcement was also investigated. In general, the mechanical performance of the polymer was enhanced at the presence of either of the reinforcements (graphene or wood fiber). The improvement in mechanical properties of the nanocomposite was notable considering that no compatibilizer was used in the manufacturing. The use of a masterbatch can promote utilization of nano-modified polymer composites on an industrial scale without modification of the currently employed processing methods and facilities.

  • 36.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gong, Guan
    Swerea SICOMP AB, Box 271, SE 941 26, Piteå, SWEDEN.
    Nyström, Birgitha
    Swerea SICOMP AB, Box 271, SE 941 26, Piteå, SWEDEN.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Swerea SICOMP AB, Box 271, SE 941 26, Piteå, SWEDEN.
    Wood Fiber Composites With Added Multi-Functionality2018Conference paper (Refereed)
    Abstract [en]

    Graphene nanoplatelets (GNPs) are used to enhance the mechanical properties and functionality of wood plastic composite (WPC) targeting applications such as de-icing or anti-icing and fast thermal diffusivity. The GNPs are integrated into neat polymer using a masterbatch containing functionalized graphene by melt compounding through a twin-screw extruder without the use of any coupling agent or compatibilizer. The same manufacturing process (melt compounding) but with the use of compatibilizer is employed to produce WPC with nano-doped matrix. The effect of different GNP loadings (up to 15 wt.%) on morphology, crystallinity, mechanical and thermal conductivity of the nanocomposites and the WPCs was investigated. It was found that both strength and modulus of nanocomposites, in tension and bending, were increased with the addition of GNPs. With the aid of MAPE compatibilizer WPCs show higher flexural strength and modulus than neat polymer. GNP has marginal effect on the flexural stress but further increases flexural modulus of WPC. The preliminary results related to the thermal conductivity of studied materials indicate that the incorporation of GNP may be beneficial for faster and more uniform heat distribution in WPC.

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    WOOD FIBER COMPOSITES WITH ADDED MULTI-FUNCTIONALITY
  • 37.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hajlane, Abdelghani
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Renbi, Abdelghani
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ouarga, Ayoub
    Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Chouhan, Shailesh Singh
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Conductive Regenerated Cellulose Fibers by Electroless Plating2019In: Fibers, ISSN 2079-6439, Vol. 7, no 5, article id 38Article in journal (Refereed)
    Abstract [en]

    Continuous metallized regenerated cellulose fibers for advanced applications (e.g. multi-functional composites) are produced by electroless copper plating. Copper is successfully deposited on the surface of cellulose fibers using commercial cyanide-free electroless copper plating package commonly available for manufacturing of printed wiring boards. The deposited copper is found to enhance the thermal stability, electrical conductivity and resistance to moisture uptake of the fibers. On the other hand, involved chemistry results in altering the molecular structure of the fibers as is indicated by the degradation of their mechanical performance (tensile strength and modulus).

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  • 38.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jantel, Ugo
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological Study on Wood and Graphene Reinforced High Density Polyethylene2022In: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability / [ed] Vassilopoulos, Anastasios; Michaud, Véronique, Lausanne: EPFL Lausanne, Composite Construction Laboratory , 2022, Vol. 1, p. 585-592Conference paper (Other academic)
    Abstract [en]

    Wear rate (WR) and coefficient of friction (COF) for high-density polyethylene (HDPE)and its composites of wood flour (WF) and/or graphene nanoplatelets (GNPs) are studied. Theinvestigation is performed by pin-on-disc test configuration on samples with different moisturecontents (dry, and samples saturated at RH of 33% and 79% in room temperature). The effect ofthe different scales of reinforcement (GNPs and WF) on these properties is discussed. Themorphological/microstructural changes in the materials induced by the motion in contact and/ormoisture content are investigated by differential scanning calorimetry (DSC). Results show thatreinforcing the polymer with WF or GNPs reduces the WR significantly, compared to neat HDPE.The hybrid reinforcements contribute to maximum improvement in wear resistance (>98%) andin the reduction of COF (>11%). The improvement in the tribological behavior of bio-basedmaterials has a significant impact on sustainable development through the improved design,durability, and environmental impact.

  • 39.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Synergistic Effect of Multiscale Reinforcement on Wear of Wood Polymer Composites2022In: PolyTrib 2022, 2022, p. 34-35Conference paper (Other academic)
  • 40.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ouarga, Ayoub
    High Throughput Multidisciplinary Research Laboratory, Mohammed VI Polytechnic University (UM6P), Lot 660—Hay Moulay Rachid, 43150 Benguerir, Morocco.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Chouhan, Shailesh Singh
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Landström, Anton
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hajlane, Abdelghani
    Laboratory of Crystallography and Materials Sciences, National Graduate School of Engineering of Caen, 6 Boulevard Maréchal Juin, 14000 Caen, France.
    Conductive Regenerated Cellulose Fibers for Multi-Functional Composites: Mechanical and Structural Investigation2021In: Materials, E-ISSN 1996-1944, Vol. 14, no 7, article id 1746Article in journal (Refereed)
    Abstract [en]

    Regenerated cellulose fibers coated with copper via electroless plating process are investigated for their mechanical properties, molecular structure changes, and suitability for use in sensing applications. Mechanical properties are evaluated in terms of tensile stiffness and strength of fiber tows before, during and after the plating process. The effect of the treatment on the molecular structure of fibers is investigated by measuring their thermal stability with differential scanning calorimetry and obtaining Raman spectra of fibers at different stages of the treatment. Results show that the last stage in the electroless process (the plating step) is the most detrimental, causing changes in fibers’ properties. Fibers seem to lose their structural integrity and develop surface defects that result in a substantial loss in their mechanical strength. However, repeating the process more than once or elongating the residence time in the plating bath does not show a further negative effect on the strength but contributes to the increase in the copper coating thickness, and, subsequently, the final stiffness of the tows. Monitoring the changes in resistance values with applied strain on a model composite made of these conductive tows show an excellent correlation between the increase in strain and increase in electrical resistance. These results indicate that these fibers show potential when combined with conventional composites of glass or carbon fibers as structure monitoring devices without largely affecting their mechanical performance.

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  • 41.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pupure, Liva
    Riga Technical University, Kalnciema Iela 6, Rīga, LV-1048, Latvia.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Analysis of long-term performance of wood polymer composites with added multifunctionality2022In: 80th International Scientific Conference of the University of Latvia - Advanced Composites and Applications: Book of Abstracts, Riga: University of Latvia , 2022, p. 9-Conference paper (Other academic)
  • 42.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pupure, Liva
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Time-dependent properties of graphene reinforced HDPE2019In: Proceedings of 9th International Conference on Composite Testing and Model Identification: Book of Abstracts / [ed] R. Joffe; L. Pupure; J. Varna; L. Wallström, 2019, article id 163Conference paper (Other academic)
  • 43.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pupure, Liva
    Department of Structural Engineering,Riga Technical University, Rīga, Latvia.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Time-dependent properties of high-density polyethylene with wood/graphene nanoplatelets reinforcement2023In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 44, no 1, p. 465-479Article in journal (Refereed)
    Abstract [en]

    The effect of graphene nanoplatelets (GNPs) on the long-term performance of wood fiber/high-density polyethylene (HDPE) composite is investigated by using short-term creep tests with an efficient, faster data analysis approach. Previously, it was shown that the addition of GNPs at 15 wt% into HDPE reduces the viscoplastic (VP) strain developed during 2 h creep by ~50%. The current study shows that 25 and 40 wt% wood content in HDPE reduce the VP strains developed during 2 h creep time by >75% with no noticeable effect of the increased wood content. However, further addition of GNPs results in more than 90% total reduction in the VP strains. The current study shows that the development of the VP strains in the hybrid composites follows Zapas model. Viscoelastic (VE) response of these composites is nonlinear and thus is described by Schapery's model. Parameters for VP and VE models are obtained from the creep experiments and were validated in a separate loading-unloading test sequence. Results show a very good agreement between experiments and predictions for the studied materials as long as the micro-damage is not present.

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  • 44.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pupure, Liva
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Riga Technical University, Institute of Construction and Reconstruction, Riga, Latvia.
    Gong, Guan
    RISE SICOMP AB, Composite materials and product development, Piteå, Sweden.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Time‐dependent properties of graphene nanoplatelets reinforced high‐density polyethylene2021In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 138, no 30, article id 50783Article in journal (Refereed)
    Abstract [en]

    The deformation of polymers at constant applied stress is one of their major drawbacks, limiting their use in advanced applications. The study of this property using classical techniques requires extensive testing over long periods of time. It is well known that reinforced polymers show improved behavior over time compared to their neat counterparts. In this study, the effect of adding different amounts of graphene nanoplatelets (GNPs) on the time‐dependent properties of high‐density polyethylene (HDPE) is investigated using short‐term creep tests and load/unload recovery tests. The results are discussed in terms of the test profile and the influence of loading history. Viscoplasticity/viscoelasticity analysis is performed using Zapas model and by comparing creep, creep compliance and pure viscoelasticity curves. The results show that the reinforcement of 15 wt% GNP have the most significant effect on the time‐dependent behavior, reducing the strain by more than 50%. The creep compliance curves show that nano‐reinforced HDPE behaves nonlinearly viscoelastically even at very low stresses. In addition to demonstrating the effect of nano‐reinforcement, the discussion of the results concludes that the influence of loading history can be quite significant and should not be neglected in the design and evaluation of material behavior.

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    fulltext
  • 45.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Sweden.
    Pupure, Liva
    Luleå University of Technology, Sweden; Riga Technical University, Latvia.
    Gong, Guan
    RISE Research Institutes of Sweden, Materials and Production, Polymeric Materials and Composites.
    Emami, Nazanin
    Luleå University of Technology, Sweden.
    Joffe, Roberts
    Luleå University of Technology, Sweden.
    Time-dependent properties of graphene nanoplatelets reinforced high-density polyethylene2021In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 138, no 30, article id 50783Article in journal (Refereed)
    Abstract [en]

    The deformation of polymers at constant applied stress is one of their major drawbacks, limiting their use in advanced applications. The study of this property using classical techniques requires extensive testing over long periods of time. It is well known that reinforced polymers show improved behavior over time compared to their neat counterparts. In this study, the effect of adding different amounts of graphene nanoplatelets (GNPs) on the time-dependent properties of high-density polyethylene (HDPE) is investigated using short-term creep tests and load/unload recovery tests. The results are discussed in terms of the test profile and the influence of loading history. Viscoplasticity/viscoelasticity analysis is performed using Zapas model and by comparing creep, creep compliance and pure viscoelasticity curves. The results show that the reinforcement of 15 wt% GNP have the most significant effect on the time-dependent behavior, reducing the strain by more than 50%. The creep compliance curves show that nano-reinforced HDPE behaves nonlinearly viscoelastically even at very low stresses. In addition to demonstrating the effect of nano-reinforcement, the discussion of the results concludes that the influence of loading history can be quite significant and should not be neglected in the design and evaluation of material behavior. © 2021 The Authors.

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  • 46.
    Al-Maqdasi, Zainab
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sott, Richard
    RISE Research Institutes of Sweden, Mölndal, 431 22, Sweden.
    Mattsson, Cecilia
    RISE Research Institutes of Sweden, Mölndal, 431 22, Sweden.
    André, Alann
    RISE Research Institutes of Sweden, Mölndal, 431 22, Sweden.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Performance of recycled glass fibers from composite parts by different treatments2022In: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability / [ed] Vassilopoulos, Anastasios; Michaud, Véronique, Lausanne: EPFL Lausanne, Composite Construction Laboratory , 2022, Vol. 6, p. 77-84Conference paper (Other academic)
    Abstract [en]

    In this work, glass fibers have been retrieved from decommissioned composite parts by three different methods. Namely, (i) pyrolysis, (ii) a novel solvolysis and (iii) a combination of solvolysis followed by pyrolysis. The techniques allowed successful recovering of sufficiently long fiber bundles (> 30 mm) that enabled separating single fibers for manual handling and testing. Single fiber tensile tests were performed to evaluate the efficiency of different recovery methods to preserve properties in comparison to the virgin fibers. The mechanical test results revealed that the stiffness of the recovered fibers has not been affected by the treatments. On the other hand, around 45% of the fiber’s strength was retained after the solvolysis process which is a comparable value to that found in literature. 

  • 47.
    Almesmari, Abdulla
    et al.
    Advanced Digital & Additive Manufacturing Center, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788; Department of Mechanical Engineering, School of Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788.
    Baghous, Nareg
    Advanced Digital & Additive Manufacturing Center, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788; Department of Mechanical Engineering, School of Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788.
    Ejeh, Chukwugozie J.
    Advanced Digital & Additive Manufacturing Center, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788; Department of Mechanical Engineering, School of Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788.
    Barsoum, Imad
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics. Advanced Digital & Additive Manufacturing Center, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates; Department of Mechanical Engineering, School of Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates.
    Abu Al-Rub, Rashid K.
    Advanced Digital & Additive Manufacturing Center, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788; Department of Mechanical Engineering, School of Engineering, Khalifa University of Science and Technology, P.O. Box 127788, Abu Dhabi, United Arab Emirates, P.O. Box 127788.
    Review of Additively Manufactured Polymeric Metamaterials: Design, Fabrication, Testing and Modeling2023In: Polymers, E-ISSN 2073-4360, Vol. 15, no 19, article id 3858Article, review/survey (Refereed)
    Abstract [en]

    Metamaterials are architected cellular materials, also known as lattice materials, that are inspired by nature or human engineering intuition, and provide multifunctional attributes that cannot be achieved by conventional polymeric materials and composites. There has been an increasing interest in the design, fabrication, and testing of polymeric metamaterials due to the recent advances in digital design methods, additive manufacturing techniques, and machine learning algorithms. To this end, the present review assembles a collection of recent research on the design, fabrication and testing of polymeric metamaterials, and it can act as a reference for future engineering applications as it categorizes the mechanical properties of existing polymeric metamaterials from literature. The research within this study reveals there is a need to develop more expedient and straightforward methods for designing metamaterials, similar to the implicitly created TPMS lattices. Additionally, more research on polymeric metamaterials under more complex loading scenarios is required to better understand their behavior. Using the right machine learning algorithms in the additive manufacturing process of metamaterials can alleviate many of the current difficulties, enabling more precise and effective production with product quality.

  • 48.
    Almgren, K. M.
    et al.
    RISE, STFI-Packforsk.
    Kerholm, M.
    RISE, STFI-Packforsk.
    Gamstedt, E. K.
    RISE, STFI-Packforsk.
    Salmen, Lennart
    RISE, STFI-Packforsk.
    Lindström, Mikael
    RISE, STFI-Packforsk.
    Effects of moisture on dynamic mechanical properties of wood fiber composites studied by dynamic FT-IR spectroscopy2008In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 27, no 16-17, p. 1709-1721Article in journal (Refereed)
    Abstract [en]

    Wood fiber reinforced polylactide is a biodegradable composite where both fibers and matrix are from renewable resources. In the development of such new materials, information on mechanical behavior on the macroscopic and the molecular level is useful. In this study, dynamic Fourier transform infrared (FT-IR) spectroscopy is used to measure losses at the molecular level during cyclic tensile loading for bonds that are characteristic of the cellulosic fibers and the polylactid matrix. This molecular behavior is compared with measured macroscopic hysteresis losses for different moisture levels. The results show that moisture ingress will transfer the load from the fibers to the matrix, and that a more efficient fiber-matrix interface would diminish mechanical losses. Although the dynamic FT-IR spectroscopy method is still qualitative, this investigation shows that it can provide information on the stress transfer of the constituents in wood fiber reinforced plastics.

  • 49.
    Almgren, Karin M.
    et al.
    RISE, STFI-Packforsk.
    Gamstedt, E. Kristofer
    RISE, STFI-Packforsk.
    Berthold, Fredrik
    RISE, STFI-Packforsk.
    Lindström, Mikael
    RISE, STFI-Packforsk.
    Moisture uptake and hygroexpansion of wood fiber composite materials with polylactide and polypropylene matrix materials2009In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 30, no 12, p. 1809-1816Article in journal (Refereed)
    Abstract [en]

    Effects of butantetracarboxylic acid (BTCA) modification, choice of matrix, and fiber volume fraction on hygroexpansion of wood fiber composites have been investigated. Untreated reference wood fibers and BTCA-modified fibers were used as reinforcement in composites with matrices composed of polylactic acid (PLA), polypropylene (PP), or a mixture thereof. The crosslinking BTCA modification reduced the out-of- plane hygroexpansion of PLA and PLA/PP composites, under water-immersed and humid conditions, whereas the swelling increased when PP was used as matrix material. This is explained by difficulties for the BTCA- modified fibers to adhere to the PP matrix. Fiber volume fraction was the most important parameter as regards out-of-plane hygroexpansion, with a high-fiber fraction leading to large hygroexpansion. Fiber-matrix wettability during processing and consolidation also showed to have a large impact on the dimensional stability and moisture uptake.

  • 50.
    Almgren, Karin M.
    et al.
    RISE, STFI-Packforsk.
    Gamstedt, E. Kristofer
    RISE, STFI-Packforsk.
    Nygård, P.
    Malmberg, F.
    Lindblad, J.
    Lindström, Mikael
    RISE, STFI-Packforsk.
    Role of fibre-fibre and fibre-matrix adhesion in stress transfer in composites made from resin-impregnated paper sheets2009In: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 29, no 5, p. 551-557Article in journal (Refereed)
    Abstract [en]

    Paper-reinforced plastics are gaining increased interest as packaging materials, where mechanical properties are of great importance. Strength and stress transfer in paper sheets are controlled by fibre-fibre bonds. In paper-reinforced plastics, where the sheet is impregnated with a polymer resin, other stress-transfer mechanisms may be more important. The influence of fibre-fibre bonds on the strength of paper-reinforced plastics was therefore investigated. Paper sheets with different degrees of fibre-fibre bonding were manufactured and used as reinforcement in a polymeric matrix. Image analysis tools were used to verify that the difference in the degree of fibre-fibre bonding had been preserved in the composite materials. Strength and stiffness of the composites were experimentally determined and showed no correlation to the degree of fibre-fibre bonding, in contrast to the behaviour of unimpregnated paper sheets. The degree of fibre-fibre bonding is therefore believed to have little importance in this type of material, where stress is mainly transferred through the fibre-matrix interface.

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