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  • 1.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Development of Constituents for Multi-functional Composites Reinforced with Cellulosic Fibers2019Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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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  • 2.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Multifunctionality and Durability of Cellulosic Fiber Reinforced Polymer Composites2022Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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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  • 3.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Dobryden, Illia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Almqvist, Nils
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Apparent Elastic Modulus of Polyethylene and its Nanocomposites Measured at Different Scales2023Ingår i: ICCM 2023 - Proceedings of the 2023 23rd International Conference on Composite Materials / [ed] Brian G. Falzon; Conor McCarthy, Queen's University Belfast , 2023Konferensbidrag (Refereegranskat)
  • 4.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gong, Guan
    RISE SICOMP AB, Fibervägen 2, 943 33 Öjebyn, Sweden.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mechanical Performance of PE Reinforced with Graphene Nanoplatelets (GNPs): Effect of Composition and Processing ParametersManuskript (preprint) (Övrigt vetenskapligt)
  • 5.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Characterization of Wood and Graphene Nanoplatelets (GNPs) Reinforced Polymer Composites2020Ingår i: Materials, E-ISSN 1996-1944, Vol. 13, nr 9, artikel-id 2089Artikel i tidskrift (Refereegranskat)
    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.

  • 6.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Swerea SICOMP AB, Box 271, SE 941 26, Piteå, SWEDEN.
    Wood Fiber Composites With Added Multi-Functionality2018Konferensbidrag (Refereegranskat)
    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
  • 7.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hajlane, Abdelghani
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Renbi, Abdelghani
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ouarga, Ayoub
    Materials Science and Nano-engineering, Mohammed VI Polytechnic University, Benguerir, Morocco.
    Chouhan, Shailesh Singh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Conductive Regenerated Cellulose Fibers by Electroless Plating2019Ingår i: Fibers, ISSN 2079-6439, Vol. 7, nr 5, artikel-id 38Artikel i tidskrift (Refereegranskat)
    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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  • 8.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Jantel, Ugo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribological Study on Wood and Graphene Reinforced High Density Polyethylene2022Ingår i: 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, s. 585-592Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 9.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Synergistic Effect of Multiscale Reinforcement on Wear of Wood Polymer Composites2022Ingår i: PolyTrib 2022, 2022, s. 34-35Konferensbidrag (Övrigt vetenskapligt)
  • 10.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ouarga, Ayoub
    High Throughput Multidisciplinary Research Laboratory, Mohammed VI Polytechnic University (UM6P), Lot 660—Hay Moulay Rachid, 43150 Benguerir, Morocco.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Chouhan, Shailesh Singh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Landström, Anton
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    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 Investigation2021Ingår i: Materials, E-ISSN 1996-1944, Vol. 14, nr 7, artikel-id 1746Artikel i tidskrift (Refereegranskat)
    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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  • 11.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pupure, Liva
    Riga Technical University, Kalnciema Iela 6, Rīga, LV-1048, Latvia.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Analysis of long-term performance of wood polymer composites with added multifunctionality2022Ingår i: 80th International Scientific Conference of the University of Latvia - Advanced Composites and Applications: Book of Abstracts, Riga: University of Latvia , 2022, s. 9-Konferensbidrag (Övrigt vetenskapligt)
  • 12.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pupure, Liva
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Time-dependent properties of graphene reinforced HDPE2019Ingår i: Proceedings of 9th International Conference on Composite Testing and Model Identification: Book of Abstracts / [ed] R. Joffe; L. Pupure; J. Varna; L. Wallström, 2019, artikel-id 163Konferensbidrag (Övrigt vetenskapligt)
  • 13.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pupure, Liva
    Department of Structural Engineering,Riga Technical University, Rīga, Latvia.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Time-dependent properties of high-density polyethylene with wood/graphene nanoplatelets reinforcement2023Ingår i: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 44, nr 1, s. 465-479Artikel i tidskrift (Refereegranskat)
    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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  • 14.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pupure, Liva
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. 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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Time‐dependent properties of graphene nanoplatelets reinforced high‐density polyethylene2021Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 138, nr 30, artikel-id 50783Artikel i tidskrift (Refereegranskat)
    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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  • 15.
    Al-Maqdasi, Zainab
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    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 tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Performance of recycled glass fibers from composite parts by different treatments2022Ingår i: 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, s. 77-84Konferensbidrag (Övrigt vetenskapligt)
    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. 

  • 16.
    Bianchi, Otávio
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials Engineering (DEMAT), Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
    Cruz, Joziel A.
    Department of Materials Engineering (DEMAT), Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
    Paim, Lucas
    Department of Materials Engineering (DEMAT), Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
    Lavoratti, Alessandra
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials Engineering (DEMAT), Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Amico, Sandro C.
    Department of Materials Engineering (DEMAT), Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
    Fernberg, Patrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Rheology, curing and time-dependent behavior of epoxy/carbon nanoparticles systems2024Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 141, nr 3, artikel-id e54821Artikel i tidskrift (Refereegranskat)
  • 17.
    Forsberg, Fredrik
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Fernberg, Patrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Petkov, Valeri
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lycksam, Henrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Efficient Use of Micro-Tomography for In-Depth Characterization of Composites2023Ingår i: ICCM 2023 - Proceedings of the 2023 23rd International Conference on Composite Materials / [ed] Brian G. Falzon; Conor McCarthy, Queen's University Belfast, Northern Ireland , 2023Konferensbidrag (Refereegranskat)
  • 18.
    Krzak, Anna
    et al.
    Scientific and Didactic Laboratory of Nanotechnology and Material Technologies, Silesian University of Technology, 44-100 Gliwice, Poland.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nowak, Agnieszka J.
    Scientific and Didactic Laboratory of Nanotechnology and Material Technologies, Silesian University of Technology, 44-100 Gliwice, Poland.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Effect of Thermomechanical Loading at Low Temperatures on Damage Development in Glass Fiber Epoxy Laminates2024Ingår i: Materials, E-ISSN 1996-1944, Vol. 17, nr 1, artikel-id 16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to the high interest in the use of glass/epoxy laminates in aerospace applications, aviation, and as cryogenic tanks, it is crucial to understand the behavior of composites under challenging environmental conditions. Polymer composites are exposed to low temperatures, including cryogenic temperatures, which can lead to the initiation of microdamage. This paper investigates damage initiation/accumulation and its influence on the properties of cross-ply woven glass fiber epoxy composites at low temperatures compared to room temperature conditions. To evaluate the influence of a low-temperature environment on the mechanical performance of glass fiber reinforced epoxy composite (GFRP) laminates, three types of test campaigns were carried out: quasi-static tensile tests and stepwise increasing loading/unloading cyclic tensile tests at room temperature and in a low-temperature environment (−50 °C). We demonstrated that the initial stiffness of the laminates increased at low temperatures. On the other hand, there were no observed changes in the type or mechanism of developed damage in the two test conditions. However, the reduction in stiffness due to the accumulated damage was more significant for the laminates tested at low temperatures (~17% vs. ~11%). Exceptions were noted in a few formulations where the extent of damage at low temperatures was insignificant (<1%) compared to that at room temperature. Since some of the studied laminates exhibited a relatively minor decrease in stiffness (~2–3%), we can also conclude that the formulation of matrix material plays an important role in delaying the initiation and formation of damage.

    Ladda ner fulltext (pdf)
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  • 19.
    Lavoratti, Alessandra
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials, Federal University of Rio Grande do Sul–UFRGS, Porto Alegre, RS, Brazil.
    Bianchi, Otávio
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of Materials, Federal University of Rio Grande do Sul–UFRGS, Porto Alegre, RS, Brazil.
    Cruz, Joziel A.
    Department of Materials, Federal University of Rio Grande do Sul–UFRGS, Porto Alegre, RS, Brazil.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Amico, Sandro Campos
    Department of Materials, Federal University of Rio Grande do Sul–UFRGS, Porto Alegre, RS, Brazil.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Impact of water absorption on the creep performance of epoxy/microcrystalline cellulose composites2024Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 141, nr 19, artikel-id e55365Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently, considerable effort has been made to study cellulose/epoxy composites. However, there is a gap when it comes to understanding the post-conditioning anomalous effect of moisture uptake on their mechanical and dynamic-mechanical properties, and on their creep behavior. In this work, up to 10.0 wt% microcrystalline cellulose (MCC) was incorporated into epoxy resin by simple mixing and sonication. Epoxy/MCC composites were fabricated by casting in rubber silicone molds, and rectangular and dog-bone test specimens were produced. The moisture uptake, dynamic mechanical, chemical, tensile, and creep behavior were evaluated. The incorporation of MCC increased the water diffusion coefficient. The changes in storage modulus and glass transition temperature, combined with Fourier-transform infrared spectroscopy analysis, evidenced that water sorption in epoxies causes both plasticization and additional resin crosslinking, although the latter is prevented by the addition of MCC. The creep strain of the composites increased by 60% after conditioning, indicating that plasticization induced by water sorption plays an important role in the long-term properties of the composites.

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  • 20.
    Nunes, Stephanie Goncalves
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement. Institute of Mechanics and Mechanical Engineering, Riga Technical University, Riga, Latvia; Materials Engineering Department, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Fernberg, Patrik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Amico, Sandro Campos
    Materials Engineering Department, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Institute of Mechanics and Mechanical Engineering, Riga Technical University, Riga, Latvia.
    Does the viscoelastic behavior of fully cured epoxy depend on the thermal history during curing?2022Ingår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 56, nr 22, s. 3439-3453Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Residual strains and shape distortions in a polymer-based composite structure may depend on the cure schedule used for manufacture. Aiming to understand the cure history effects, the influence of the curing “path” (time tc and temperature Tc path during curing) on viscoelastic (VE) response of a fully cured (FC) (alpha = 0.992) epoxy was investigated. Five different “families” of the same epoxy were manufactured in constraint-free conditions using different sets of curing parameters. Then, tensile tests were performed at different temperatures (T = 30 to 110 °C), and the time-temperature superposition principle (TTSP) and Schapery’s type of linear viscoelastic (VE) model, accounting for physical aging of specimens tested at high temperature, were used. The results show that the VE properties of the studied epoxy are independent of the curing history provided that at the end all specimens are fully cured. Also, the physical aging rate at high temperatures of all “families” is the same and it can be described by a simple aging-temperature independent equation reported in Nunes et al1 It is expected that curing history of unconstrained and fully cured epoxy has an insignificant effect on final viscoelastic behavior, a knowledge which could assist in developing more time and cost-efficient cure cycles.

  • 21.
    Pupure, Liva
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gong, Guan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Effect of Nano-reinforcement on the Time-dependent Properties of Graphene Modified High Density PolyethyleneManuskript (preprint) (Övrigt vetenskapligt)
  • 22.
    Pupure, Liva
    et al.
    Department of structural engineering, Riga Technical University, Kipsalas 6A, LV-1048, Riga, Latvia.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Department of structural engineering, Riga Technical University, Kipsalas 6A, LV-1048, Riga, Latvia.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pakrastins, Leonids
    Department of structural engineering, Riga Technical University, Kipsalas 6A, LV-1048, Riga, Latvia.
    Experimental Parameter Identification for 3D Nonlinear Viscoelastic Material Model2023Ingår i: ICCM 2023 - Proceedings of the 2023 23rd International Conference on Composite Materials / [ed] Brian G. Falzon; Conor McCarthy, Queen's University Belfast, Northern Ireland , 2023Konferensbidrag (Refereegranskat)
  • 23.
    Pupure, Liva
    et al.
    Institute of Structural engineering, Riga Technical University, Latvia.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Institute of Structural engineering, Riga Technical University, Latvia.
    Gailitis, Rihards
    Institute of Structural engineering, Riga Technical University, Latvia.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pakrastins, Leonids
    Institute of Structural engineering, Riga Technical University, Latvia.
    Development of methodology for experimental parameter identification for inelastic 3D material model2022Ingår i: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability / [ed] Vassilopoulos, Anastasios; Michaud, Véronique, Lausanne, Lausanne: EPFL Lausanne, Composite Construction Laboratory , 2022, Vol. 6, s. 282-289Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Lately due to advancement of materials, structures and modeling capacities demand for 3D nonlinear material models implemented in commercial software’s and codes have increased. In order to obtain such implemented model, firstly the model itself and the methodology for experimental parameter identification have to be established. The overall goal is to create a 3D material model, that could account for viscolpasticity, viscoelasticity and damage. Within this study the viscoplastic behavior in axial and lateral direction will be analyzed, thus obtaining the materials 3D viscoplastic behavior. Experimental data for various materials are analyzed. The results showed that viscoplastic strain has the same time and stress dependency in axial and lateral direction. The only difference is in the ration of axial and lateral strain, which is characterized by a single multiplication factor within viscoplastic material model. 

  • 24.
    Vadivel, Hari Shankar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Pupure, Liva
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap. Institue of Structural Engineering and Reconstruction, Riga Technical University, LV 1658, Riga, Latvia.
    Joffe, Roberts
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kalin, Mitjan
    Laboratory for tribology and interface nanotechnology, University of Ljubljana, 1000, Ljubljana, Slovenia.
    Emami, Nazanin
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Time-dependent properties of newly developed multiscale UHMWPE composites2022Ingår i: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 105, artikel-id 107400Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultra-high molecular-weight polyethylene (UHMWPE) composites reinforced with Graphene Oxide (GO), Nanodiamonds (ND), and Short Carbon Fibres (SCF) are characterised for their mechanical performance in tensile and short-term creep tests. A methodology to separate and analyse the materials’ viscoelastic (VE) and viscoplastic (VP) responses is applied and evaluated. The results show a clear dependence of the performance on size scale/morphology of the reinforcements. All composites show time-dependent VP responses that can be expressed by Zapas model and fit the experimental data with high accuracy. The analysed VE strains and creep compliance curves reveal the nonlinear stress-dependent VE behaviour of all composites at all tested creep stresses. Combining multiscale reinforcements results in an improvement that surpasses that of individual reinforcements. The results of this work offer valuable input for the design and selection of polymer-based materials in demanding applications where prolonged use under service conditions is critical to their performance.

  • 25.
    Viesturs, Lācis
    et al.
    Riga Technical university, Latvia.
    Alens, Šņepsts
    Riga Technical university, Latvia.
    Andrejs, Pupurs
    Riga Technical university, Latvia.
    Al-Maqdasi, Zainab
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Experimental and numerical analysis of heat dissipation in hybrid carbon/glass thin-ply composites for multifunctional applications2022Ingår i: 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. 3, s. 122-128Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Thermal behavior of hybrid carbon/glass thin-ply laminates with different layer thickness ratios were investigated experimentally. Two different approaches were used for applying thermal loads: in one experiment small-scale external heater was attached on the surface of laminate specimen; in the second approach cyclic mechanical loading with high frequency was applied to generate internal heating within materials. In both experiments transient temperature distribution along the thickness of specimens was measured and recorded using high performance thermal imaging camera. Obtained results demonstrate temperature distribution in reference and hybrid laminate layers during the transient and steady state thermal conditions. Relatively large differences between carbon/epoxy and glass/epoxy layers were found in terms of internal heat generation and heat transfer. Parametric analysis results on reference and various hybrid lay-ups from this study could aid the lay-up design for composites in multifunctional applications with various thermal processes.

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