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  • 1. Asp, Leif
    Multifunctional composite materials for energy storage in structural load paths2013In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 42, no 4, p. 144-149Article in journal (Refereed)
    Abstract [en]

    This paper presents an overview of the research performed to date by a Swedish interdisciplinaryteam of scientists striving to develop multifunctional composite materials for storage of electric energy in mechanical load paths. To realise structural batteries from polymer composites, research pursued on carbon fibres for use as negative electrode in the battery as well as on polymer electrolytes for use as polymer matrix in the composite is reported. The work on carbon fibres comprises characterisation of the electrochemical capacity of commercial carbon fibre grades and how this is affected by mechanical load. Co-polymers are studied for their multifunctional performance with respect to lithium ion conductivity and stiffness. Also, rational processing of these polymer electrolytes and the effect of processing on their properties are addressed

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    FULLTEXT01
  • 2.
    Carlson, Tony
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ordéus, Daniel
    Swerea SICOMP AB.
    Wysocki, M.
    Swerea SICOMP AB.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    CFRP structural capacitor materials for automotive applications2011In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 40, no 6/7, p. 311-316Article in journal (Refereed)
    Abstract [en]

    In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy prepreg woven lamina separated by a polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and tearing force. The developed structural carbon fibre reinforced polymer (CFRP) capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential.

    Download full text (pdf)
    FULLTEXT01
  • 3.
    Ekstedt, Sofia
    et al.
    Swerea SICOMP AB.
    Wysocki, Maciej
    Swerea SICOMP AB.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Structural batteries made from fibre reinforced composites2010In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 39, no 3-5, p. 148-150Article in journal (Refereed)
    Abstract [en]

    Structural, fibre reinforced, battery prototypes with two types of electrolyte matrix material (a gel and a solid polymer) have been manufactured. This was to confirm the concept of using carbon fibres as current collector in the anode as well as providing a mechanical load-carrying functionality. As a result, functioning batteries with gel electrolyte have been produced and their properties have been characterised.

  • 4. Frishfelds, Vilnis
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Modelling of particle deposition during impregnation of dual-scale fabrics2011In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 40, no 2, p. 65-69Article in journal (Refereed)
    Abstract [en]

    The motion of particles through a system of permeable fibre bundles is considered. The system is discretisised with Voronoi diagrams and the dissipation rate of energy is minimised with respect to the stream function in a system with periodic boundary conditions. The flow of the particles is in the transversal direction to the fibre bundles and the particles are hindered to move out of the plane allowing for two-dimensional calculations. The motion of particles is assumed to be slow with respect to the flowrate so that particles are driven by the Stokesian force for stationary particles. In this case, the flow distribution is essentially dependent on the particle configuration and strictly follows the motion of particles. When testing different sizes of the particles, it is shown that there is a qualitative agreement between model and experiments previously performed. In particular, stationary flow leads to particle depositions in front of the fibre bundles and small particles move into the fibre bundles while large ones are stuck at the border

  • 5.
    Gong, G.
    et al.
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Nyström, Birgitha
    Swerea SICOMP AB, Box 271, 941 26, Piteå.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Enhanced thermal stability and flame retarding properties of recycled polyethylene based wood composites via addition of polyethylene/nanoclay masterbatch2013In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 42, no 6, p. 244-255Article in journal (Refereed)
    Abstract [en]

    Barrier and mechanical properties of wood powder composites based on recycled polyethylene (RPE) were modified using a commercial nanoclay masterbatch. X-ray diffraction, dynamic rheology and thermogravimetric analysis measurements showed that nanoclay from the selected masterbatch was well dispersed and formed a percolation network in both virgin and RPEs. The resulting nanocomposites promoted the thermal stability of matrix significantly. Modification efficiency of nanoclay, however, was evidently influenced by the type of matrix, where the strongest effect was achieved in a low viscosity virgin high density PE. The masterbatch was incorporated into an industrial formula designed extrusion quality RPE/wood flour composite. Processing procedures, mainly compounding cycles, and material composition, mainly clay content and type of coupling agent, were optimised. Two extrusion cycles led to higher uniformity of resulting composites than one cycle. Addition of a coupling agent, which has medium viscosity and plenty functional groups, led to enhanced tensile strength. The twice compounded composites were well stiffened and strengthened via combination of 6 wt-% clay and medium viscosity coupling agent. All composites without the addition of nanoclay burned faster after ignition and dripped much earlier and more compared to the composites containing nanoclay even with as small amount as 3 wt-% and being compounded once. The material with 6 wt-% clay showed the best sample integrity and burned slowest of all the tested composites. Furthermore, no dripping during combustion was seen for this material. This study shows that the incorporation of nanoclay using the selected masterbatch can effectively improve the flame retarding properties of RPE based wood composites

  • 6.
    Gong, Guan
    et al.
    Swerea SICOMP AB.
    Nyström, Birgitha
    Swerea SICOMP AB.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Development of polyethylene/nanoclay masterbatch for use in wood plastic composites2013In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 42, no 4, p. 167-175Article in journal (Refereed)
    Abstract [en]

    In this work, organoclay reinforced high density polyethylene (HDPE) nanocomposites were prepared at lab scale using a batch mixer. Processing conditions, maleic anhydride modified polyethylene (MAPE) type and MAPE/clay weight ratio, were optimized. The microstructure of the resultant nanocomposites was analysed by XRD and melt rheology tests and flexural properties and thermal stability were evaluated. Three types of MAPEs with different melt flow index (MFI) and MA content all improved interaction between HDPE and clay, and promoted clay dispersion. Nanocomposites where the MAPE with MFI most similar to HDPE was used showed the best exfoliation of clay and strongest HDPE-clay interface. Mechanical properties were slightly improved while thermal stability was distinctly enhanced in these HDPE nanocomposites compared to neat HDPE and HDPE nanocomposite without MAPE. The prepared HDPE nanocomposites show potential to improve thermal stability of wood plastic composites for structural applications providing.

  • 7. Hietala, Maiju
    et al.
    Niinimäki, Jouko
    University of Oulu.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Processing of wood chip-plastic composites: effect on wood particle size, microstructure and mechanical properties2011In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 40, no 2, p. 49-56Article in journal (Refereed)
    Abstract [en]

    Wood chips were used as raw material in extrusion of wood-plastic composites. Wood-plastic composites with similar to 50 wt-% wood content were manufactured by using two different compounding methods. Dried and undried wood chips were used to investigate the effect of wood moisture content on the wood particle size and whether the drying process could be carried out in the same step. Wood particle properties were measured using optical fibre analysis. Microscopical methods were used to examine the microstructure of wood particles. Furthermore, the prepared composites' mechanical properties were studied. The particle size of wood chips was significantly reduced during extrusion in both processing methods. The undried wood chips had higher aspect ratios in comparison with the dried wood chips after extrusion. Despite the higher aspect ratio, the mechanical properties of composites manufactured with undried wood chips were not better than the properties of composites with dried wood chips

  • 8.
    Hooshmand, Saleh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cho, Sung-Woo
    University of Borås.
    Skrifvars, Mikael
    University of Borås.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Melt spun cellulose nanocomposite fibres: comparison of two dispersion techniques2014In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 43, no 1, p. 15-24Article in journal (Refereed)
    Abstract [en]

    Bio-based continuous fibers were processed by melt spinning of cellulose acetate butyrate (CAB) and cellulose nanowhiskers (CNW) as well as environmental friendly plasticizer, triethyl citrate (TEC). Homogeneous dispersion of the CNW in CAB was achieved by solvent exchange to ethanol using sol-gel process. The appropriate amounts of well dispersed CNW organo-gel (2 and 10 wt%) as well as 15 wt% TEC were compounded with the dissolved CAB in ethanol followed by magnetic string, solution casting and grinding. Melt spinning of compounded CAB/TEC and CAB/TEC/CNW were carried out using a twin-screw micro extruder in continuous mode to decrease the residence time of materials and avoid thermal degradation. Afterwards, the fibers were solid-state drawn to enhance the mechanical properties. The addition of the CNW restricted the drawability of the fibers to a factor of 1.5. The tensile test data showed that 2 wt% CNW had no noticeable effect on modulus and tensile strength of the fibers while 10 wt% CNW increased the modulus and tensile strength by 58% and 36% respectively. Drawing, in general, provided greater stiffness and strength but sacrificed the ductility of the fibers. The microscopy studies showed that the fiber diameters were in the range of 350-450 μm for as-spun fibers and 300-350 μm for drawn fibers and no defect and increased surface roughness could be detected on the surface of the both as-spun and drawn composite fibers. Furthermore, The thermal properties, viscoelastic behavior as well as crystallinity properties of the fibers were characterized by TGA, DMTA and XRD.

  • 9.
    Högberg, Sofie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Motion of dispersed carbon nanotubes during impregnation of fabrics2011In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 40, no 2, p. 70-79Article in journal (Refereed)
    Abstract [en]

    Interest is growing in the development of hierarchical composites, in which nanoscale particles are used alongside the traditional microscale reinforcing fibres. To produce high quality multiscale materials, knowledge of mechanisms governing nanofibre distribution and orientation is crucial. In this work, analysis and numerical simulations are used to model the motion of dispersed carbon nanotubes during impregnation of dual scale fabrics in composites manufacturing. Results suggest that nanofibre displacement and orientation is mainly deterministic on mesoscale, while typically random on microscale. The randomising Brownian torque may still influence the motion and trigger the fibre to make 180 degrees rotations in the former, however, when acting together with the fluid shear. Fibre deposition may lead to a total blockage of the flow within the microchannels, whereas only minor deposition is expected in the mesochannels.

  • 10.
    Loukil, Mohamed Sahbi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hussain, W.
    Kirti, A.
    Pupurs, Andrejs
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Varna, Janis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thermoelastic constants of symmetric laminates with cracks in 90-layer: application of simple models2013In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 42, no 4, p. 157-166Article in journal (Refereed)
    Abstract [en]

    The change of thermoelastic properties of cross-ply and quasi-isotropic laminates with intralaminar cracks in layers is analysed. Predictions are performed using previously derived general expressions for stiffness of symmetric damaged laminates as dependent on crack density and crack face opening and sliding. It is shown that the average crack opening displacement can be linked with the average value of axial stress perturbation between two cracks. Using this relationship, analytical shear lag and Hashin’s models, developed for axial modulus, can be applied for calculating thermal expansion coefficients, in-plane moduli and Poisson’s ratios of damaged laminates. The approach is evaluated using finite element method and it is shown that the accuracy is rather similar to that in axial modulus calculation.

  • 11.
    Marklund, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Varna, Janis
    Micromechanical modelling of wood fibre composites2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 2, p. 118-123Article in journal (Refereed)
    Abstract [en]

    A concentric cylinder model for an N-phase composite with orthotropic properties of constituents was previously presented by the authors. With only minor modifications the model allows for including also free hygroexpansion terms in the elastic stress-strain relationship in order to deal with orthotropic phase swelling. Thus the effect of wood fibre ultrastructure and cell wall hygroelastic properties on wood fibre composite hygroexpansion may be analysed. Multiscale modelling was performed to calculate the hygroexpansion coefficients of both the fibre cell wall and the aligned wood fibre composite. Furthermore, the fibre's helical structure leads to an extension-twist coupling and thus a free fibre will deform axially and also rotate upon loading in longitudinal fibre direction. Within the composite, however, the fibre rotation will be restricted. Therefore, the decision was to compare the composite performance in the two extreme cases (i) free rotation (ii) no rotation of the fibre in the composite.

  • 12. Nilsson, Sören
    et al.
    Bredberg, Anders
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Effects of CFRP laminate thickness on bending after impact strength2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 2, p. 61-66Article in journal (Refereed)
    Abstract [en]

    This paper describes a series of experiments set out to explore the strength of bending loaded impacted monolithic composite panels with different thicknesses. Two laminate thicknesses are tested, both exposed to the same impact event in a drop tower with 35 J using a spherical tup with a radius of 8 mm. Accompanying tests in compression are performed and reported to allow evaluation of the full effects of bending. A limited fractographic analysis is also performed to study damage distribution after impact as well as after mechanical tests. It has been demonstrated that damage distribution through the thickness affects the bending properties of the laminate as the failure load was lower when the side with the largest delamination was loaded in compression. As expected it has also been demonstrated that the far field failure strain is higher at bending compared to compression loading.

  • 13.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Sain, Mohini
    University of Toronto.
    Novel bionanocomposites: processing properties and potential applications2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 9-10, p. 396-405Article in journal (Refereed)
    Abstract [en]

    The demand for environmental sustainability has resulted in a great interest in finding new materials that are biodegradable and environmentally friendly. Therefore, materials derived from natural resources are now being extensively studied. Preparation of novel biocomposites based on nanocelluloses has drawn specific attention. It is expected that cellulose nanocomposites will open new areas for applications in medicine, packaging, electronics, the automotive sector, construction and other areas. This article presents a new research field of bionanocomposites where different types of nanocelluloses are used as reinforcements in biopolymers. Isolation of cellulose nanofibres and nanowhiskers from different sources, and processing technologies for the composites, are described and discussed. The main difficulty when producing cellulose based nanocomposites is to disperse the reinforcement in the polymer matrix without degradation of the biopolymer or the reinforcing phase. This can be addressed by improving the interaction (compatibility) between nanofibres and the matrix and by using suitable processing methods. The study of alignment of the nanocelluloses by using magnetic field is discussed and the nanocomposites' mechanical properties, based on the findings from different studies, are presented. Finally, some examples of future nanocomposites are discussed.

  • 14. Olsson, Jimmy
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Olofsson, Kurt
    Swerea SICOMP AB.
    Design of experiment study of compression moulding of SMC2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 9/10, p. 428-433Article in journal (Refereed)
    Abstract [en]

    The effect of vacuum assistance, mould temperature and ram velocity on the void transport and flow behaviour for sheet moulding compound (SMC) have been investigated with a design of experiment approach of the compression moulding phase. The relative amount of voids has been quantified with a high voltage insulation test and the flow behaviour has been quantified with image analysis of samples moulded with coloured SMC. In conclusion, the setting of high vacuum, low ram velocity and low mould temperature creates a homogeneous flow and minimises the amount of voids.

  • 15. Pupurs, Andrejs
    et al.
    Varna, Janis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Unidirectional composite in mechanical fatigue: modelling debond growth from fibre breaks2010In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 39, no 3-5, p. 128-136Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to analyse fibre/matrix debond crack growth during high stress cyclic tension-tension loading of unidirectional composites. The debond crack evolution analysis is based on fracture mechanics concepts that mode II energy release rate calculations are performed analytically for long debonds, where crack growth is self-similar, and numerically for short debonds by finite element method in combination with virtual crack closure technique. From the calculation results simple expressions are derived for an arbitrary mechanical and thermal loading case. Finally, the obtained expressions are applied in Paris law for debond growth simulations in cyclic tension-tension loading.

  • 16.
    Svanberg, J. Magnus
    Luleå tekniska universitet.
    Shape distortion of non-isothermally cured composite angle bracket2002In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 31, no 9, p. 398-404Article in journal (Refereed)
    Abstract [en]

    A simulation tool for prediction of shape distortion and residual stresses has been developed by implementing a new material model in the general purpose FE package ABAQUS. To validate the simulation tool, three thick wailed angle brackets were manufactured under non-isothermal conditions. Predicted temperatures, degree of cure, and shape distortions were then compared with the experimental values for the thick walled angle brackets. Predicted and experimental values show good agreement, which verifies that the simulation procedure is reliable under non-isothermal curing conditions

  • 17. Szpieg, Magdalena
    et al.
    Wysocki, Maciej
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Recycled polypropylene aimed as composites precursor material2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 9-10, p. 412-418Article in journal (Refereed)
    Abstract [en]

    The aim of this research is to assess the stability and processability of recycled PP materials for their suitability for use as matrix material in polymer composite. The work comprises development and characterisation of matrix precursors from recycled polypropylene. The reused PP considered comes from two sources: PP from the self reinforced PP PURE® processing scrap and an automotive grade developed to offer an even material quality. To assess the thermal stability of two PP qualities for subsequent composite manufacturing, oxidation induction time (OIT), melting point (Tm), decomposition temperature (Td) and viscosity (μ) were investigated. The results indicate, that PURE® processing scrap is very well stabilised and therefore suitable for multiple processing, whereas the automotive grade recycled PP cannot be used for this purpose. Fibres, for subsequent composite preforming were spun by melt spinning from the PURE® scrap processing and its mechanical properties were characterised.

  • 18.
    Szpieg, Magdalena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Wysocki, Maciej
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Reuse of polymer materials and carbon fibres in novel engineering composite materials2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 9-10, p. 419-425Article in journal (Refereed)
    Abstract [en]

    The present work was devoted to the development of a technique for manufacture of a novel engineering material from carbon fibres and thermoplastic matrix recyclates. Fibre preforms were manufactured employing a papermaking technique for dispersing the carbon fibres. The polypropylene (PP) matrix recyclate was reprocessed into a film. The carbon fibre preforms and PP films were stacked and composite materials were subsequently manufactured by press forming. The mechanical behaviour of carbon fibre preforms was characterised by a compaction test and compared to the results obtained by consolidation test of the carbon fibres reinforced PP composites. The consolidation experiments were found to follow the trend from compaction tests allowing prediction of the amount of polymer material needed, fibre volume fraction as well as composites thickness. The resulting dispersion of fibres and void content were evaluated by microscopy.

  • 19. Talreja, Ramesh
    Defect damage mechanics: Broader strategy for performance evaluation of composites2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 2-4, p. 49-54Article in journal (Refereed)
    Abstract [en]

    Damage mechanics is a well established field wherein analyses and methodologies are developed to provide bases for evaluation of materials response and for structural design. Although this field has been very active for composites in the past two decades, the approaches taken still largely treat homogenised microstructures of composites, leaving out influences of manufacturing induced defects in initiation and progression of damage. The present paper illustrates the importance of accounting for such defects by taking examples of voids in unidirectional fibre reinforced composites and of fibre clusters in short fibre composites. The explicit incorporation of defects is suggested as a broader damage mechanics strategy by which failure analysis and the consequent performance evaluation of composite structures must be conducted

  • 20. Vargas, Natalia Herrera
    et al.
    Mathew, Aji P.
    Wang, Luyi
    Luleå tekniska universitet.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Randomly oriented and aligned cellulose fibres reinforced with cellulose nanowhiskers and prepared by electrospinning2011In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 40, no 2, p. 57-64Article in journal (Refereed)
    Abstract [en]

    The goal of this work was to prepare random and aligned cellulose fibres by electrospinning. Cellulose acetate (CA) was used as a matrix and a mixture of acetic acid and acetone (1:1) was used as an solvent. Cellulose nanowhiskers (CNWs) with different concentrations (0-5 wt-%) were used as reinforcement. Microscopy studies showed fibres with smooth surfaces, different morphologies and diameters ranging between 200 and 3300 nm. It was found that the fibre diameters decreased with increased CNW contents. The microscopy studies also indicated well aligned fibres. Results from dynamic mechanical thermal analysis indicated improved mechanical properties with the addition of CNWs. The storage modulus of electrospun CA fibres increased from 81 to 825 MPa for fibres with 1 wt-% CNW at room temperature. X-ray analysis showed that the electrospun CA fibres had a crystalline nature and that there was no significant change in crystallinity with the addition of CNWs

  • 21.
    Varna, Janis
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rozite, Liva
    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.
    Pupurs, Andrejs
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Non-linear behaviour of PLA based flax composites2012In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 41, no 2, p. 49-60Article in journal (Refereed)
    Abstract [en]

    The mechanical behaviour of polylactic acid/flax fibre composite in tension was investigated by analysing elastic properties and loading curves. The observed non-linearity was attributed to microdamage, viscoelastic and viscoplastic response, suggesting Schapery's type of model for viscoelasticilty and Zapas' model for viscoplasticity. It was found that after loading at stress levels below the maximum possible, the elastic modulus is not affected, and therefore, damage does not need to be included in the material model. Viscoplastic and viscoelastic strain development was analysed in creep and strain recovery tests at several high stress levels. The identified and validated material model is non-linear viscoelastic and viscoplastic with slight non-linearity even in the elastic strain term. It appears that there is no region of linear viscoelasticity for this material. Non-linear elasticity, viscoelasticity and viscoplasticity are equally responsible for the observed non-linearity in the tensile tests

  • 22.
    Wysocki, Maciej
    et al.
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Toll, Staffan
    Chalmers University of Technology.
    Larsson, Ragnar
    Chalmers University of Technology.
    Two phase continuum modelling of composites consolidation2009In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, no 2, p. 93-97Article in journal (Refereed)
    Abstract [en]

    In this paper, a finite element (FE) code for modelling of pressure driven axisymmetric consolidation of composite material from commingled yarns is presented. The proposed model is developed on the basis of a two phase continuum model incorporated in an FE framework. The applicability of the code to axisymmetric geometries is demonstrated by analysis of the consolidation, i.e. resin infiltration and fibre bundle network deformation, of a GF/PP pressure vessel. In this numerical example, two different sets of processing conditions are presented. Based on these analysis results conclusions on the process ability of the investigated vessel configuration and manufacturing scheme are drawn and processing recommendations are given.

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