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  • 51.
    Juntti, Magnus
    et al.
    Aeronautical Research Institute of Sweden.
    Asp, Leif
    Olsson, Robin
    Aeronautical Research Institute of Sweden.
    Assessment of evaluation methods for the mixed-mode bending test1999In: Journal of composites technology & research, ISSN 0884-6804, E-ISSN 1945-7537, Vol. 21, no 1, p. 37-48Article in journal (Refereed)
    Abstract [en]

    The evaluation procedure for the mixed mode bend (MMB) delamination test is assessed with focus on analytically equivalent evaluation models, expressed in load-displacement or load-only parameters. In particular, the assessment concerns the sensitivity of the interlaminar toughness to the test rig forces as well as material and geometrical properties of the specimen. For a typical example, neglect of test rig forces causes a 10% relative error in the calculated mixed mode ratio when using methods based on load only. When all additional forces were considered, both evaluation methods produced almost identical results. However, evaluation based on load only is sensitive to variations in specimen flexural modulus and dimensions and had a larger scatter. The application of crack length corrections for calculating the Mode I component is discussed in detail. The findings of the study are summarized in recommendations for the MMB test procedure and its subsequent evaluation.

  • 52.
    Leijonmarck, S.
    et al.
    KTH, Stockholm.
    Carlson, T.
    Swerea SICOMP, Mölndal.
    Kjell, M.H.
    KTH, Stockholm.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Swerea SICOMP, Mölndal.
    Lindbergh, G.
    KTH, Stockholm.
    Maples, H.
    Department of Chemical Engineering, Imperial College London, London, United Kingdom.
    Bismarck, A.
    Department of Chemical Engineering, Imperial College London, London, United Kingdom; Institute of Materials Chemistry and Research, University of Vienna, Vienna, Austria.
    Coated carbon fibre battery half-cells for structural battery composites2013In: Proceedings of the 19th International Conference on Composite Materials: ICCM 2013, Montreal (Canada), ICCM , 2013, p. 5342-5343Conference paper (Refereed)
  • 53.
    Leijonmarck, S.
    et al.
    Swerea SICOMP AB.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Division of Materials Science, Composite Centre Sweden, Luleå University of Technology.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Division of Materials Science, Composite Centre Sweden, Luleå University of Technology.
    Lindbergh, G.
    Division of Applied Electrochemistry, Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics. Swerea SICOMP AB.
    Direct electropolymerization of polymer electrolytes onto carbon fibers - A route to structural batteries?2014In: 16th European Conference on Composite Materials, ECCM 2014: Seville, Spain, 22 June- 26 June 2014, European Conference on Composite Materials, ECCM , 2014Conference paper (Refereed)
    Abstract [en]

    In an effort to further reduce weight of carbon fibre reinforced composites, the concept of structural batteries has arisen. A structural battery is a multifunctional material managing both energy storage and enabling of structural integrity. More specific, the carbon fibres in the composites are used as negative electrode in a Li-ion battery. A crucial part of such a battery is the preparation of a thin, ionically conductive and stiff polymer matrix. One route to realize this is the use of electropolymerization, which can cover each individual fibre with polymer. In this study, the surface morphology of coated carbon fibres is investigated with electron microscopy and atomic force microscopy. Additionally, the curing degree as a function of process temperature during polymerization is tested.

  • 54.
    Leijonmarck, Simon
    et al.
    Division of Applied Electrochemistry, Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Carlson, Tony
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindbergh, Göran
    Division of Applied Electrochemistry, Department of Chemical Engineering and Technology, KTH Royal Institute of Technology.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Maples, Henry A.
    Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Bismarck, Alexander
    Polymer & Composite Engineering (PaCE) Group, Department of Chemical Engineering, Imperial College London, South Kensington Campus.
    Solid polymer electrolyte-coated carbon fibres for structural and novel micro batteries2013In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 89, p. 149-157Article in journal (Refereed)
    Abstract [en]

    We report a method to deposit a thin solid polymer electrolyte (SPE) coating around individual carbon fibres for the realisation of novel battery designs. In this study an electrocoating method is used to coat methacrylate-based solid polymer electrolytes on to carbon fibres. By this approach a dense uniform, apparently pinhole-free, poly(methoxy polyethylene glycol (350) monomethacrylate) coating with an average coating thickness of 470 nm was deposited around carbon fibres. Li-triflate, used as supporting electrolyte remained in the coating after the electrocoating operation. The Li-ion content in the solid polymer coating was found to be sufficiently high for battery applications. A battery device was built employing the SPE coated carbon fibres as negative electrode demonstrating reversible specific capacity of 260 mAh/g at low currents (C/10), suggesting that these coated carbon fibres can be employed in future structural composite batteries.

  • 55.
    Marklund, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Multiscale methodology for matrix failure prediction in non-crimp fabric composites2010In: ECCM 14: 14th European Conference on Composite Materials ; June 7 - 10, 2010, Budapest, Hungary, Budapest: BUTE Dep. of Polymer Engineering , 2010Conference paper (Refereed)
    Abstract [en]

    This paper examines the possibility of performing a combined micro-meso approach to model transverse matrix failure within the bundle structure for non-crimp fabric composites. Failure initiation sites are predicted considering the discrete bundle structure, its volume fraction and fibre volume fraction within bundles, as well as the triaxial stress state built up from the combined contributions of mechanical loading and thermal/chemical shrinkage due to curing at elevated temperature. An analytical expression for average strain in a bundle with simplified geometry is used to link the micro- and meso length scales. The work presented here is intended to give further guidelines in the creation of a black-box modelling tool, which utilises traditional laminar analyses for non-crimp fabric composites consisting of layers having “effective” ply properties.

  • 56.
    Marklund, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Olsson, Robin
    Swerea SICOMP AB, Mölndal.
    Transverse strength of unidirectional non-crimp: multiscale Modelling2014In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 65, p. 47-56Article in journal (Refereed)
    Abstract [en]

    A multiscale approach is used to predict transverse tensile and transverse compressive strength of unidirectional non-crimp fabric (NCF) composites. Numerical analysis on fibre/matrix scale is performed to obtain the transverse strength of the fibre bundle to be further used in an analytical mesoscale model to predict the strength of the unidirectional NCF composite. Design of unidirectional layer composites with the same fibres, interface, matrix and volume fractions as in the bundle is suggested as an alternative method for bundle strength determination. Good agreement of both methods for bundle transverse strength determination is demonstrated. The simple analytical model used on mesoscale gives accurate predictions of the tensile transverse strength whereas the compressive strength is underestimated. The necessity of including bundle waviness in models when bidirectional NCF composites are analyzed is demonstrated by FEM stress analysis and by experimental data showing differences in transverse cracking pattern due to bundle waviness.

  • 57.
    Marklund, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nilsson, Sören
    Swerea SICOMP AB.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Matrix failure prediction in polymer composites including effects of temperature and degree of cure2011In: Composites 2011: ECCOMAS Thematic Conference, 3rd International Conference on the Mechanical Response of Composites, Hannover, 21 - 23 September, 2011 / [ed] R. Rolfes; E.L. Jansen, Hannover: LUH, Institut für Statik und Dynamik , 2011, p. 579-586Conference paper (Other academic)
  • 58.
    Marklund, Erik
    et al.
    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.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Damage progression in non-crimp fabric composites2011In: Non-crimp fabrics composites: manufacturing, properties and applications, Cambridge: Woodhead Publishing Materials , 2011Chapter in book (Refereed)
  • 59.
    Marklund, Erik
    et al.
    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.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Stiffness and strength modelling of non-crimp fabric composites2011In: 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference 2011, Red Hook: Curran Associates, Inc., 2011, Vol. 1, p. 679-695Conference paper (Refereed)
    Abstract [en]

    This work comprises methodologies for micro-meso stiffness modelling and limited analysis for strength prediction. It is intended to formulate some guidelines and recommendations when modelling NCF composites mechanical performance. For both micro- and meso stiffness modelling, analytical models are compared to FE investigations considering idealised structures. Important aspects when modelling matrix failure of NCF composite bundles are presented to highlight some of the challenges in future modelling. Possible failure criteria for modelling matrix failure within fibre bundles have been investigated; their strength, problems and weaknesses are revealed.

  • 60.
    Melin, L. Gunnar
    et al.
    Luleå tekniska universitet.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Strain rate dependency of the mechanical properties of a CF/EP composite studied by Moiré photography1997Report (Other academic)
  • 61. Melin, L.Gunnar
    et al.
    Asp, Leif
    Dynamic transverse tensile behavior of a carbon/epoxy composite: Monitoring crack initiation and propagation1998In: American Society for Composites: 13th technical conference on composite materials, American Society of Civil Engineers (ASCE), 1998, p. 354-370Conference paper (Refereed)
  • 62.
    Melin, L.Gunnar
    et al.
    Luleå tekniska universitet.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Effects of strain rate on transverse tension properties of a carbon/epoxy composite: Studied by moire photography1999In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 30, no 3, p. 305-316Article in journal (Refereed)
    Abstract [en]

    The dependence on strain rate of the mechanical properties of a high performance carbon fibre/epoxy composite loaded in transverse tension has been investigated. Dog-bone shaped specimens have been tested in quasi-static and dynamic loading conditions. The dynamic tests were performed in a split Hopkinson bar at strain rates between 100 and 800 s-1. A moiré technique combined with high-speed photography, at framing rates of 0.25-1 MHz, was used for extraction of the local strain fields. The transverse mechanical properties were found to have weak or no dependence on strain rate. The average transverse modulus did not depend on strain rate, whereas the strain to and stress at failure were found to increase slightly with increased strain rate. For these dog-bone shaped specimens the strain evaluated by conventional Hopkinson bar technique was found to underestimate the true strain field measured by moiré technique. Finally, the moiré technique facilitated crack-propagation monitoring in real time. Crack speeds up to 2300 m s-1 were measured at transverse crack propagation.

  • 63. Melin, L.Gunnar
    et al.
    Neumeister, Jonas
    Pettersson, Kaj B.
    Johansson, Hans
    Asp, Leif
    Evaluation of four composite shear test methods by digital speckle strain mapping and fractographic analysis2000In: Journal of composites technology & research, ISSN 0884-6804, E-ISSN 1945-7537, Vol. 22, no 3, p. 161-172Article in journal (Refereed)
    Abstract [en]

    Four methods to determine composite interlaminar shear strength (ILSS) are evaluated. In particular, the recently devised inclined double-notch shear test (IDNS) is compared with three existing and more established methods: the Iosipescu test, the short three-point bending test (S3PB) and the double-notch compression tesl (DNC). The uniformity of strain field in the test region in a real test situation - which is the crucial test method quality parameter - is investigated by strain mapping using digital speckle photography. The measured strain fields are compared with FE-calculated strains representing ideal conditions and both known advantages and drawbacks of the different methods are confirmed. The IDNS test produces the most uniform strain fields and also consistently high ILSS values. A fractographic analysis indicates shear separation over a major part of the fracture surfaces of all specimen types; typical shear cusps were found over about 80% of the IDNS fracture surface and in about 50% to 70% in the other specimens. For the Iosipescu tests, failure initiation could be ascribed to initiation in tension at defects. Experimentally determined stress-strain responses in shear exhibit a distinct variation among the different methods. For the best methods, a notable material softening was observed prior to failure. Observed formation of shear cusps is believed to be the primary cause for this softening of the composite material studied here.

  • 64. Nilsson, K.-F.
    et al.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Alpman, J.
    Delamination buckling and growth at global buckling1997In: Damage and failure of interfaces: proceedings of the First International Conference on Damage and Failure of Interfaces, Vienna, Austria, 22 - 24 September 1997 / [ed] Hans-Peter Rossmanith, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1997Conference paper (Refereed)
  • 65. Nilsson, K.-F.
    et al.
    Asp, Leif
    Alpman, J.E:
    Nystedt, L.
    Delamination buckling and growth for delaminations at different depths in a slender composite panel2001In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 38, no 17, p. 3039-3071Article in journal (Refereed)
    Abstract [en]

    A numerical and experimental investigation for delamination buckling and growth for slender composite panels loaded in compression is presented. The investigated panels consisted of 35 plies in a cross-ply layup with artificially embedded delaminations inserted after three, five or seven plies from the upper surface. The tests clearly and consistently showed that for all delamination depths, delaminated panels failed by delamination growth slightly below the global buckling load of the undamaged panel, whereas the undelaminated panels failed in compression at global buckling. The analysis was done with a finite element based computational model that accounts for contact between delaminated members and fracture mode separation and where crack propagation was simulated with a moving mesh scheme. For all delamination depths, the analysis showed a dramatic increase in the energy release rate when global buckling takes place. Features seen in the tests were captured in the computational analysis. Excellent agreement with tests was found for loads at which delaminated members buckle, the load for onset of delamination growth and the evolution of delamination, e.g., delamination shape and out-of-plane displacements.

  • 66.
    Nilsson, K.F.
    et al.
    Aeronautical Research Institute of Sweden.
    Asp, Leif
    Sjögren, A.
    Aeronautical Research Institute of Sweden.
    On transition of delamination growth behaviour for compression loaded composite panels2001In: International Journal of Solids and Structures, ISSN 0020-7683, E-ISSN 1879-2146, Vol. 38, no 46-47, p. 8407-8440Article in journal (Refereed)
    Abstract [en]

    This paper presents a combined numerical and experimental study of slender composite panels loaded in compression with artificial delaminations at two different depths. The study was motivated by finite element analyses where this change in delamination depth induced a transition in the direction of delamination growth along with a change in the basic fracture modes and stability. Tests were then carried out to verify the transition in delamination growth. The predicted transitions were to a large extent also seen in the tests. The paper gives an outline of the computational model, which includes contact between delaminated members, calculation of energy release rate with fracture mode separation by an approximate as well as a reliable method for general layups, and moving mesh scheme to account for delamination growth. The experimental work includes monitoring of delamination growth by C-scan and acoustic emission along with a detailed fractographical study. The correlation between experimental observations and computed results are discussed in detail.

  • 67. 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.

  • 68.
    Nilsson, Sören
    et al.
    Swerea SICOMP AB, Mölndal.
    Bredberg, Anders
    SAAB, Linköping.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Effects of CFRP laminate thickness on the bending after impact strength2008In: 13th European Conference on Composite Materials: 2-5 June 2008, Stockholm, Sweden, 2008Conference paper (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. Due to the aim to decrease manufacturing cost future structures are expected to have a higher degree of integration and complexity. More integrated structures give fewer articles and fewer steps in the manufacturing chain. Also the maximum thickness of laminated composite structures is increasing in aircraft structures. For example, the wing spars of the inner wings as well as the central wing box in modern aircraft are made from composite laminates with thickness exceeding 40 mm. As a consequence of this development there are more interlaminar loads (bending, transverse shear etc) within composite structures. Therefore the composite  structures must sustain high out of plane loads (bending, transverse shear etc). To increase the potential and reduce conservatism during design there is a need to increase the knowledge regarding residual strength of out of plane loaded impact damaged composite structure. This study was launched as a first attempt to study the effects of bending load at different laminate thicknesses of a composite structure. Here two laminate thicknesses are tested, both exposed to the same impact threat. 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.

  • 69.
    Nilsson, Sören
    et al.
    Swerea SICOMP AB.
    Bredberg, Anders
    Saab Aerostructures.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Size effects on strength of notched CFRP laminates loaded in bending2009In: ICCM 17, Edinburgh: 17th International Conference on Composite Materials ; 27 Jul 2009 - 31 Jul 2009, Edinburgh International Convention Centre, Edinburgh, UK, London: IOM Communications , 2009Conference paper (Refereed)
    Abstract [en]

    This paper describes a series of experiments set out to explore the strength of notched monolithic composite panels with different dimensions and notch size loaded in bending. Two laminate thicknesses and two widths are tested. When varying the width, also the notch diameter is varied to retain a constant W/D- ratio. 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 failure initiation. It has been shown that a larger hole results in a lower failure strain although the W/D-ratio is the same. As expected it has also been demonstrated that the far field failure strain is higher in bending than in compression.

  • 70. Olsson, R.
    et al.
    Asp, Leif
    Nilsson, S.
    Sjögren, A.
    Review of some key developments in the analysis of the effects of impact upon composite structures2001In: Composite structures : theory and practice / [ed] Peter Grant; Carl Q. Rousseau, ASTM International, 2001, p. 12-28Conference paper (Refereed)
  • 71.
    Olsson, Robin
    et al.
    Swerea SICOMP AB.
    Marklund, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jansson, Niklas
    Volvo Aero Corporation.
    Strength of NCF composite bundles under biaxial stress2011In: Composite materials for structural performance: towards higher limits: of the 32nd Risø International Symposium on Materials Science ; 5 - 9 September 2011, Roskilde, Denmark / [ed] S. Fæster, Roskilde: Risø National Laboratory for Sustainable Energy, Danmarks Tekniske Universitet , 2011Conference paper (Refereed)
  • 72.
    Scobbie, K.
    et al.
    Huntsman Advanced Materials, Basel.
    Tsotra, P.
    Huntsman Advanced Materials, Basel.
    Hoge, J.
    Huntsman Advanced Materials, Basel.
    Christou, P.
    Huntsman Advanced Materials, Basel.
    Knipprath, C.
    Composites Centre, Cranfield University.
    Skordos, A. A.
    Composites Centre, Cranfield University.
    Nilsson, S.
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Pickett, A.K.
    ESI GmbH, Eschborn.
    Development of high toughness epoxy resins for liquid composite moulding2009In: ICCM 17, Edinburgh: 17th International Conference on Composite Materials ; 27 Jul 2009 - 31 Jul 2009, Edinburgh International Convention Centre, Edinburgh, UK, London: IOM Communications , 2009Conference paper (Refereed)
    Abstract [en]

    Epoxy matrix systems combining high toughness with rheological behaviour appropriate for liquid composite moulding are developed in this work. The neat resin and carbon laminate properties of a variety of novel formulations are evaluated and compared with reference materials to identify promising technologies for the development of advanced matrix materials suitable for infusion processing

  • 73. Sjögren, A.
    et al.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Greenhalgh, E.S.
    Hiley, M.J.
    Interlaminar crack propagation in CFRP: effects of temperature and loading conditions2002In: Composite Materials: Testing, Design, And Acceptance Criteria, ASTM International, 2002, p. 235-252Conference paper (Refereed)
  • 74.
    Sjögren, Anders
    et al.
    Aeronautical Research Institute of Sweden.
    Asp, Leif
    Effects of temperature on delamination growth in a carbon/epoxy composite under fatigue loading2001In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 24, no 2-4, p. 179-184Article in journal (Refereed)
    Abstract [en]

    This paper presents a study of delamination growth in HTA/6376C carbon fibre/epoxy laminates. Tests were conducted under Mode I, Mode II and mixed-mode static and fatigue loading at both ambient conditions and elevated temperature. The results show that the strain energy release rate threshold values for delamination growth under fatigue loading are significantly lower than the critical energy release rates in static tests. At elevated temperature, the threshold values in the fatigue loading were only about 10% of the critical values in the static tests. A fractographic analysis of the delamination growth revealed that the fracture surfaces generated at elevated temperature generally were similar to the fracture surfaces generated at room temperature. Nevertheless, some differences in morphology of the fracture surfaces were observed, and their effect on the static and fatigue delamination growth is discussed in detail.

  • 75.
    Szpieg, Magdalena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Giannadakis, Konstantinos
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Viscoelastic and viscoplastic behavior of a fully recycled carbon fibre-reinforced maleic anhydride grafted polypropylene modified polypropylene composite2012In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, no 13, p. 1633-1646Article in journal (Refereed)
    Abstract [en]

    The effect of maleic anhydride grafted polypropylene (MAPP) coupling agents on properties of a new composite made of recycled carbon fibers and recycled polypropylene (rCF/[rPP + MAPP]) was studied experimentally. This new material presented significantly improved properties, compared to the previous generation, without the addition of MAPP (Giannadakis K, Szpieg M and Varna J. Mechanical performance of recycled carbon fibre/PP. Exp Mech 2010; published online.). This was mostly attributed to improvement of the fiber/matrix interface. The inelastic and time-dependent behavior of the MAPP modified composite material in tension was analyzed. A series of quasi-static tensile and creep tests were performed to identify the material model, which accounts for: (a) damage-related stiffness reduction, (b)development of stress and time-dependent irreversible strains described as viscoplasticity, (c) nonlinear viscoelastic behavior. The damage-related stiffness reduction was found to be less than 10%. Although damage-dependent stiffness was not the main source of nonlinearity, it was included in the inelastic material model. In creep tests, it was found that the time and stress dependence of viscoplastic strains follows a power law, which makes the determination of the parameters in the viscoplasticity model relatively simple. The viscoelastic response of the composite was found to be linear in the investigated stress domain. The material model was validated in constant stress rate tensile tests.

  • 76.
    Szpieg, Magdalena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Wysocki, M.
    SICOMP AB, Swedish Institute of Composites.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Novel composites from recycled constituents2009In: 24th annual technical conference of the American Society for Composites 2009 and 1st Joint Canadian-American Technical Conference on Composites: Newark, Delaware, USA, 15 - 17 September 2009 / [ed] John W. Gillespie, Red Hook, NY: Curran Associates, Inc., 2009, Vol. 4, p. 2651-2661Conference paper (Refereed)
    Abstract [en]

    Only a small fraction of the waste generated by use and manufacturing of carbon-based composites is currently reused. However, due to European Union (EU) regulations and limited amount of landfilling, the industry is forced to consider recycling solutions already during the manufacturing process. The following work is devoted to the development of a technique for manufacture of novel engineering materials from recycled carbon fibres and thermoplastic matrix. Fibre preforms are manufactured employing a papermaking technique for dispersing the carbon fibres. The polypropylene (PP) matrix was reprocessed into a film. The carbon fibre preforms and PP films were stacked and composite materials were subsequently manufactured by press forming and evaluated.

  • 77. 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.

  • 78.
    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.

  • 79. Wysocki, M.
    et al.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Toll, S.
    Larsson, R.
    Finite element model for axisymmetric consolidation of thermoplastic composite materials2005In: Proceedings. ASC 20th Annual Technical Conference, 2005Conference paper (Refereed)
  • 80.
    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.

  • 81.
    Wysocki, Maciej
    et al.
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Toll, Staffan
    Chalmers University of Technology.
    Larsson, Ragnar
    Chalmers University of Technology.
    Two-phase continuum modelling of composites consolidation2008In: 13th European Conference on Composite Materials: 2-5 June 2008, Stockholm, Sweden, 2008Conference paper (Refereed)
    Abstract [en]

    In this paper a finite element 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 a FEframework. 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.

  • 82.
    Wysocki, Maciej
    et al.
    SICOMP AB, Swedish Institute of Composites.
    Toll, Staffan
    Chalmers University of Technology.
    Asp, Leif
    Consolidation of commingled yarn based composites: continuum modelling2007In: Proceedings of COMP07: 6th International Symposium on Advanced Composites 16-18 May, 2007, Corfu, Greece, 2007Conference paper (Refereed)
    Abstract [en]

    Pressure driven consolidation of a component made from a commingled yarn composite is modelled and simulated. A finite-element code is developed based on a novel two-phase continuum framework. The applicability of the code to complex geometries is demonstrated by analysis of the consolidation, i.e. resin infiltration and preform deformation, of an axisymmetric filament wound GF/PP pressure vessel. In conclusion, the consolidation of the vessel is prevented by the loading mode where the pressure is applied on the interior. To succeed in manufacturing of this type of pressure vessel, a use of an loosely wound preform that allows extension in the fibre direction is suggested.

  • 83.
    Wysocki, Maciej
    et al.
    SICOMP AB, Swedish Institute of Composites.
    Toll, Staffan
    Royal Institute of Technology, Stockholm.
    Larsson, Ragnar
    Chalmers University of Technology.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Anisotropic and tension-compression asymmetric model for composites consolidation2010In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 41, no 2, p. 284-294Article in journal (Refereed)
    Abstract [en]

    A constitutive model for anisotropic and tension-compression asymmetric response of a fibrous preform is developed and solved using a FE software. Applicability of the method to complex geometries is demonstrated by analysis the consolidation of an axisymmetric filament wound pressure vessel made from commingled yarns. Three different winding patterns are considered. In conclusions, the consolidation of the whole vessel, except at the opening, is prevented by the loading mode where the pressure is applied on the interior. To succeed in manufacturing of this type of pressure vessel, use of an oversized preform that allows extension in the fibre direction is suggested. The proposed model provides precisely the required spatial distribution of fibre excess for consolidation without fibre tension: on average a 2 % oversize for both winding patterns.

  • 84. Wysocki, Maciej
    et al.
    Toll, Staffan
    Chalmers University of Technology.
    Larsson, Ragnar
    Chalmers University of Technology.
    Asp, Leif
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hyperelastic constitutive models for consolidation of commingled yarn based composites2008In: FPCM-9. The 9th International Conference on Flow Processes in Composite Materials: Montréal (Québec), Canada 8 - 10 July 2008, 2008Conference paper (Refereed)
12 51 - 84 of 84
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