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  • 1.
    Ansari, Farhan
    et al.
    KTH Royal Institute of Technology, Sweden.
    Sjöstedt, Anna
    KTH Royal Institute of Technology, Sweden.
    Larsson, Per Tomas
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    Berglund, Lars A.
    KTH Royal Institute of Technology, Sweden.
    Wågberg, Lars
    KTH Royal Institute of Technology, Sweden.
    Hierarchical wood cellulose fiber/epoxy biocomposites: Materials design of fiber porosity and nanostructure2015In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 74, p. 60-68Article in journal (Refereed)
    Abstract [en]

    Delignified chemical wood pulp fibers can be designed to have a controlled structure of cellulose fibril aggregates to serve as porous templates in biocomposites with unique properties. The potential of these fibers as reinforcement for an epoxy matrix (EP) was investigated in this work. Networks of porous wood fibers were impregnated with monomeric epoxy and cured. Microscopy images from ultramicrotomed cross sections and tensile fractured surfaces were used to study the distribution of matrix inside and around the fibers - at two different length scales. Mechanical characterization at different relative humidity showed much improved mechanical properties of biocomposites based on epoxy-impregnated fibers and they were rather insensitive to surrounding humidity. Furthermore, the mechanical properties of cellulose-fiber biocomposites were compared with those of cellulose-nanofibril (CNF) composites; strong similarities were found between the two materials. The reasons for this, some limitations and the role of specific surface area of the fiber are discussed.

  • 2.
    Asp, Leif
    et al.
    RISE, Swerea, Swerea SICOMP.
    Nilsson, S.
    Aeronautical Research Institute of Sweden, FFA.
    Singh, S.
    DERA Farnborough.
    An experimental investigation of the influence of delamination growth on the residual strength of impacted laminates2001In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 32, no 9, p. 1229-1235Article in journal (Refereed)
    Abstract [en]

    This study concerns an experimental investigation to establish data for validation of residual strength models for impacted composite panels. The work focuses on compression tests of panels with embedded artificial delaminations at various depths. Accompanying tests on undamaged and impact-damaged panels are reported and the relevance of the tests on artificially delaminated panels is assessed. In the experiments both the artificially delaminated and the impacted plates failed by delamination growth. Consequently, the same mechanism governed failure in the two cases. Hence, the artificially delaminated plate test is reliable for validation of methods developed for analysis of the residual strength of impact-damaged panels. However, for impacted plates, the load at global plate buckling was consistently 10% lower than that of the artificially delaminated plates and 20% lower than that of the undamaged plates. Hence, conservative prediction of the global buckling load of an impacted composite panel require s methods that consider influence of stiffness reduction of the damaged zone. © 2001 Elsevier Science Ltd. All rights reserved.

  • 3.
    Chinga-Carrasco, Gary
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Zarna, Chiara
    NTNU, Norway.
    Rodríguez-Fabià, Sandra
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Leirset, Ingebjörg
    RISE Research Institutes of Sweden.
    Tanase-Opedal, Mihaela
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Molteberg, Dag
    Norske Skog Saugbrugs, Norway.
    Echtermeyer, Andreas
    NTNU, Norway.
    Hindersland, Leif
    Alloc AS, Norway.
    Side streams from flooring laminate production – Characterisation and recycling in biocomposite formulations for injection moulding2022In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 153, article id 106723Article in journal (Refereed)
    Abstract [en]

    Side streams were collected from three locations in a flooring factory and their suitability in biocomposite formulations was assessed. The side stream (S3) that contained mainly residues from high-density fibreboards (HDF) was selected for further material testing. The effect of different fractions of S3, thermomechanical pulp (TMP) fibres and polylactic acid (PLA) were assessed in terms of their mechanical, melt flow and thermal properties. A biocomposite made from PLA, 20 wt% TMP fibres and 10 wt% S3 revealed a significant increase in modulus (5800 MPa), compared to the neat PLA (3598 MPa), and a similar melt-flow index (MFI = 4.5). The tensile strength was however somewhat reduced from 66 to 58 MPa. Importantly, numerical modelling and simulations were applied to demonstrate that building a model chair out of biocomposite can potentially reduce the material volume by 12% while maintaining similar load bearing capacity, compared to neat PLA. © 2021 The Author(s)

  • 4.
    Costa, Sergio
    et al.
    RISE Research Institutes of Sweden, Materials and Production, Polymeric Materials and Composites.
    Zrida, Hana
    Gestamp Hardtech AB, Sweden.
    Olsson, Robin
    RISE Research Institutes of Sweden, Materials and Production, Polymeric Materials and Composites.
    Herráez, Miguel
    University Rey Juan Carlos, Spain.
    Östlund, Rickard
    Gestamp Hardtech AB, Sweden.
    A unified physically-based finite deformation model for damage growth in composites2022In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 161, article id 107103Article in journal (Refereed)
    Abstract [en]

    Two 3D homogenized models for damage growth in a unidirectional (UD) composite ply are simplified and merged into a unified model. The fibre kinking behaviour is based on fibre kinking theory handled in a finite deformation framework. The nonlinear shear behaviour is pressure dependent and is modelled by combining damage and friction on the fracture plane. Fibre kinking growth and transverse behaviour are modelled with a single damage variable. This allows both modes to occur simultaneously and mutually influence each other in an efficient and physically-based way. For validation the model is tested against micro-mechanical Finite Element (FE) simulations under pure longitudinal compression and influenced by shear. The results show nearly perfect agreement for stiffness, strength and crushing stress. The model validation is performed against two different components under three-point bending and a quasi-static crash scenario. Both simulation show good correlation with experiments, validating thus the present unified model. © 2022 The Author(s)

  • 5.
    Craven, R.
    et al.
    Imperial College London.
    Iannucci, L.
    Imperial College London.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Delamination buckling: A finite element study with realistic delamination shapes, multiple delaminations and fibre fracture cracks2010In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 41, no 5, p. 684-692Article in journal (Refereed)
    Abstract [en]

    This paper presents a finite element model of a carbon fibre composite laminate with multiple delaminations of realistic shape and including fibre fracture cracks loaded under compression. The modelling technique is initially applied on circular and elliptical delaminations of single ply sublaminates, which are compared with existing analytical solutions. The techniques are then applied to models with multiple delaminations of realistic shape and their behaviour in buckling and post-buckling is captured. An inverse method is used to determine the stiffness reduction caused by the damage, and shows significant stiffness reduction caused by peanut shaped delaminations. When fibre fracture cracks are added, their contribution to further stiffness reduction is minimal but they have some significant effects on the buckling shapes. © 2010 Elsevier Ltd. All rights reserved.

  • 6.
    Dweib, M.A.
    et al.
    Natl. Univ. I..
    Vahlund, Fredrik
    RISE, Swerea, Swerea SICOMP.
    Ó Brádaigh, C.M.
    Natl. Univ. I..
    Fibre structure and anisotropy of glass reinforced thermoplastics2000In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 31, no 3, p. 235-244Article in journal (Refereed)
    Abstract [en]

    The fibre structure and orientation distribution of two commercially available glass mat thermoplastics reinforced by continuous glass fibre was studied to investigate the anisotropic behaviour under compression moulding and mechanical loading, and to investigate the influence of the fibre structure and orientation on the anisotropic behaviour. Circular samples were deformed into ellipses when moulded, due to the anisotropic fibre orientation. The fibre content and orientation were examined in different locations of the elliptically deformed specimens. X-ray pictures were taken of the material in order to develop images of the fibres, before and after compression moulding. In another procedure, the matrix was burned off and the fibre network structures were studied in each case. A CCD camera was used to scan the fibres as digital images to measure the orientation distribution functions of the fibres. The fibre orientation measuring process was facilitated by subroutines implemented in the source code of the public domain NIH-image analysis software using simulated Fraunhofer diffraction.

  • 7.
    Edgren, Fredrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Asp, Leif
    RISE, Swerea, Swerea SICOMP.
    Approximate analytical constitutive model for non-crimp fabric composites2005In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 36, no 2 SPEC. ISS., p. 173-181Conference paper (Refereed)
    Abstract [en]

    In this paper, a study set on development and validation of constitutive models to account for out-of-plane fibre waviness in Non-crimp fabric (NCF) composites is presented. For this purpose, a mathematical model based on Timoshenko beam theory applied on curved beams, representing wavy tows in a NCF composite layer is employed. Stiffness knock-down factors operating at the ply level are established and introduced in laminate theory. The developed models are validated on laminates by comparison between predictions and experimental data as well as by comparison with numerical results for a cross-ply laminate. Application of the models on NCF composite laminates (cross-ply and quasi-isotropic) reveals that the models successfully predict laminate elastic properties. © 2004 Elsevier Ltd. All rights reserved.

  • 8.
    Gamstedt, E.K.
    et al.
    Royal Institute of Technology (KTH).
    Skrifvars, Mikael
    RISE, Swerea, Swerea SICOMP.
    Jacobsen, T.K.
    LM Glasfiber A/S.
    Pyrz, R.
    Aalborg University.
    Synthesis of unsaturated polyesters for improved interfacial strength in carbon fibre composites2002In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 33, no 9, p. 1239-1252Article in journal (Refereed)
    Abstract [en]

    Carbon fibres are gaining use as reinforcement in glass fibre/polyester composites for increased stiffness as a hybrid composite. The mechanics and chemistry of the carbon fibre-polyester interface should be addressed to achieve an improvement also in fatigue performance and off-axis strength. To make better use of the versatility of unsaturated polyesters in a carbon fibre composite, a set of unsaturated polyester resins have been synthesized with different ratios of maleic anhydride, o-phthalic anhydride and 1,2-propylene glycol as precursors. The effective interfacial strength was determined by micro-Raman spectroscopy of a single-fibre composite tested in tension. The interfacial shear strength with untreated carbon fibres increased with increasing degree of unsaturation of the polyester, which is controlled by the relative amount of maleic anhydride. This can be explained by a contribution of chemical bonding of the double bonds in the polymer to the functional groups of the carbon fibre surface. © 2002 Elsevier Science Ltd. All rights reserved.

  • 9.
    Khalili, Pooria
    et al.
    Chalmers University of Technology, Sweden.
    Blinzler, Brina
    Chalmers University of Technology, Sweden.
    Kádár, Roland
    Chalmers University of Technology, Sweden.
    Blomqvist, Per
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Sandinge, Anna
    RISE Research Institutes of Sweden, Safety and Transport, Fire Technology.
    Bisschop, Roeland
    RISE Research Institutes of Sweden, Safety and Transport, Safety Research.
    Liu, Xiaoling
    University of Nottingham Ningbo China, China.
    Ramie fabric Elium® composites with flame retardant coating: Flammability, smoke, viscoelastic and mechanical properties2020In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 137, article id 105986Article in journal (Refereed)
    Abstract [en]

    This investigation studied the utilization of intumescent thermal resistive mats to provide surface protection to the core natural fibre-reinforced Elium® composite structural integrity. The intumescent mats contained flame retardant (FR) i.e. expandable graphite (EG) with four different expansion ratios and alumina trihydrate (ATH). All natural fibre thermoplastic composites were fabricated using a resin infusion technique. The impact of char thickness and chemical compositions on the flammability and smoke properties was investigated. It was found that surface protection significantly reduced the peak heat release rate, total smoke release, smoke extinction area and CO2 yield, and substantially enhanced UL-94 rating, time to ignition and residual char network, depending on the EG exfoliation ratio, ATH and mineral wool fibre. The glass transition temperature increased for the FR composites containing EG with lower expansion ratio. Inclusion of intumescent mats increased the strength of the composites while it had a negative effect on the modulus. 

  • 10.
    McElroy, Mark
    et al.
    NASA Langley Research Center, USA.
    Jackson, Wade
    NASA Langley Research Center, USA.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Hellström, Peter
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Tsampas, Spyros
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Pankow, Mark
    North Carolina State University, USA.
    Interaction of delaminations and matrix cracks in a CFRP plate, Part I: A test method for model validation2017In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 103, p. 314-326Article in journal (Refereed)
    Abstract [en]

    Isolating and observing the damage mechanisms associated with low-velocity impact in composites using traditional experiments can be challenging, due to damage process complexity and high strain rates. In this work, a new test method is presented that provides a means to study, in detail, the interaction of common impact damage mechanisms, namely delamination, matrix cracking, and delamination-migration, in a context less challenging than a real impact event. Carbon fiber reinforced polymer specimens containing a thin insert in one region were loaded in a biaxial-bending state of deformation. As a result, three-dimensional damage processes, involving delaminations at no more than three different interfaces that interact with one another via transverse matrix cracks, were observed and documented using ultrasonic testing and X-ray computed tomography. The data generated by the test is intended for use in numerical model validation. Simulations of this test are included in Part II of this paper.

  • 11.
    Molker, Henrik
    et al.
    Volvo Car Corporation, Sweden; Chalmers University of Technology, Sweden.
    Gutkin, Renaud
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Asp, Leif E.
    Chalmers University of Technology, Sweden.
    Implementation of failure criteria for transverse failure of orthotropic Non-Crimp Fabric composite materials2017In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 92, p. 158-166Article in journal (Refereed)
    Abstract [en]

    In this paper a set of failure criteria for Non-Crimp Fabric (NCF) reinforced composites is implemented in a Finite Element (FE) software. The criteria, implemented at the ply level, predict transverse failure of NCF reinforced composites, in particular accounting for their inherent orthotropic properties. Numerical simulations are compared with tests on specimens with a generic design feature found in automotive structures. The current implementation enables correct prediction of failure mode and location.

  • 12.
    Nilsson, Greger
    et al.
    RISE, Swerea, Swerea SICOMP.
    Fernberg, S.P.
    Luleå University of Technology.
    Berglund, L.A.
    Luleå University of Technology.
    Strain field inhomogeneities and stiffness changes in GMT containing voids2002In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 33, no 1, p. 75-85Article in journal (Refereed)
    Abstract [en]

    During compression moulding of glass mat thermoplastics (GMT), voids may form. However, it is not clear whether voids are as critical to mechanical performance in GMT as in thermoset composites. The present investigation also considers the general problem of damage mechanisms in GMT. Conventional tensile tests, acoustic emission, a stiffness degradation test and a speckle technique for strain field measurements are used as well as optical microscopy of polished cross-sections. The void content (up to 5%) does not significantly influence the strength or stiffness degradation process. The reason is the large inhomogeneity of the strain fields in GMT. Failure occurs in locally soft regions and void effects are of secondary importance. Details of the failure process are discussed, emphasising the large local strains in matrix-rich regions. © 2001 Published by Elsevier Science Ltd.

  • 13.
    Nordlund, M.
    et al.
    Luleå University of Technology.
    Fernberg, Patrik
    RISE, Swerea, Swerea SICOMP.
    Lundström, T.S.
    Luleå University of Technology.
    Particle deposition mechanisms during processing of advanced composite materials2007In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 38, no 10, p. 2182-2193Article in journal (Refereed)
    Abstract [en]

    Liquid composite moulding of advanced composite materials often comprises infiltration of a particle-filled resin into a multi-scale porous fabric. These injections/infusions are subject to severe particle depositions inside the reinforcement, leading to undesired inhomogeneous mechanical and functional properties. Hence, the mechanisms for particle depositions are investigated by detailed meso-scale experiments, analysed by microscopic imaging and micro-particle image velocimetry, and macroscopic infusions of a biaxial non-crimp fabric. It is shown that two main particle deposition mechanisms are filtration during fibre bundle impregnation and filtration induced by stationary flow through fibre bundles. It is also clarified where in the reinforcement the particles will deposit. Finally, a number of suggestions on how to process advanced composite materials with a more homogeneous particle distribution are launched. © 2007 Elsevier Ltd. All rights reserved.

  • 14.
    Oldenbo, M.
    et al.
    Volvo Car Corporation.
    Fernberg, Patrik
    RISE, Swerea, Swerea SICOMP.
    Berglund, L.A.
    Royal Institute of Technology.
    Mechanical behaviour of SMC composites with toughening and low density additives2003In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 34, no 9, p. 875-885Article in journal (Refereed)
    Abstract [en]

    A new type of SMC material (Flex-SMC) developed for automotive exterior body panels has been investigated. Flex-SMC contains hollow glass micro-spheres and thermoplastic toughening additives. A conventional SMC (Std-SMC) was used as a reference material. Materials were tested in monotonic tension and compression. Stiffness degradation with strain as well as fracture toughness was determined. In situ SEM was used to study failure mechanisms. Flex-SMC has a density almost 20% lower than Std-SMC and has higher impact resistance. The damage threshold strain of the Flex-SMCs is higher than for Std-SMC. Flex-SMCs have more than twice the fracture toughness of Std-SMC. The major reason identified is that Flex-SMCs shows extensive fibre pullout. © 2003 Elsevier Ltd. All rights reserved.

  • 15.
    Olsson, Robin
    RISE, Swerea, SICOMP.
    Analytical prediction of damage due to large mass impact on thin ply composites2015In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 72, p. 184-191Article in journal (Refereed)
    Abstract [en]

    This article presents analytical models for predicting large mass impact response and damage in thin-ply composite laminates. Existing models for large mass impact (quasi-static) response are presented and extended to account for damage phenomena observed in thin-ply composites. The most important addition is a set of criteria for initiation and growth of bending induced compressive fibre failure, which has been observed to be extensive in thin ply laminates, while it is rarely observed in conventional laminates. The model predictions are compared to results from previous tests on CFRP laminates with a plain weave made from thin spread tow bands. The experiments seem to confirm the model predictions, but also highlight the need to include the effects of widespread bending induced fibre failure into the structural model

  • 16.
    Prakobna, Kasinee
    et al.
    KTH Royal Institute of Technology, Sweden.
    Berthold, Fredrik
    RISE, Innventia. KTH Royal Institute of Technology, Sweden.
    Medina, Lilian
    KTH Royal Institute of Technology, Sweden.
    Berglund, Lars A.
    KTH Royal Institute of Technology, Sweden.
    Mechanical performance and architecture of biocomposite honeycombs and foams from core-shell holocellulose nanofibers2016In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 88, p. 116-122Article in journal (Refereed)
    Abstract [en]

    CNFs (cellulose nanofibers) based on holocellulose have a pure cellulose fibril core, with a hemicellulose coating. The diameter is only around 6-8 nm and the hemicellulose surface coating has anionic charge. These CNFs are used to prepare honeycomb and foam structures by freeze-drying from dilute hydrocolloidal suspensions. The materials are compared with materials based on "conventional" cellulose CNFs from sulfite pulp with respect to mechanical properties in compression. Characterization methods include FE-SEM of cellular structure, and the analysis includes comparisons with similar materials from other types of CNFs and data in the literature. The honeycomb structures show superior out-of-plane properties compared with the more isotropic foam structures, as expected. Honeycombs based on holocellulose CNFs showed better properties than sulfite pulp CNF honeycombs, since the cellular structure contained less defects. This is related to better stability of holocellulose CNFs in colloidal suspension.

  • 17.
    Pupurs, Andrejs
    et al.
    RISE, Swerea, SICOMP. Luleå University of Technology, Sweden.
    Varna, J.
    Luleå University of Technology, Sweden.
    Loukil, Mohamed
    RISE, Swerea, SICOMP.
    Ben Kahla, H.
    Luleå University of Technology, Sweden.
    Mattsson, David
    RISE, Swerea, SICOMP.
    Effective stiffness concept in bending modeling of laminates with damage in surface 90-layers2016In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 82, p. 244-252Article in journal (Refereed)
    Abstract [en]

    Simple approach based on Classical Laminate Theory (CLT) and effective stiffness of damaged layer is suggested for bending stiffness determination of laminate with intralaminar cracks in surface 90-layers and delaminations initiated from intralaminar cracks. The effective stiffness of a layer with damage is back-calculated comparing the in-plane stiffness of a symmetric reference cross-ply laminate with and without damage. The in-plane stiffness of the damaged reference cross-ply laminate was calculated in two ways: (1) using FEM model of representative volume element (RVE) and (2) using the analytical GLOB-LOC model. The obtained effective stiffness of a layer at varying crack density and delamination length was used to calculate the A, B and D matrices in the unsymmetrically damaged laminate. The applicability of the effective stiffness in CLT to solve bending problems was validated analyzing bending of the damaged laminate in 4-point bending test which was also simulated with 3-D FEM.

  • 18.
    Rodriguez Fabia, Sandra
    et al.
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Zarna, Chiara
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Chinga Carrasco, Gary
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    A comparative study of kraft pulp fibres and the corresponding fibrillated materials as reinforcement of LDPE- and HDPE-biocomposites2023In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 173, article id 107678Article in journal (Refereed)
    Abstract [en]

    Cellulose nanofibrils (CNFs) have been proposed as reinforcement for thermoplastic polymers due to their potentially superior mechanical properties. However, it seems still uncertain how the reinforcement ability of CNFs compares to cheaper pulp fibres, and how the suspected potential of CNFs can be fully utilized in biocomposites. Therefore, this study presents a direct comparative investigation of kraft pulp fibres and their fibrillated materials as reinforcement of high- or low-density polyethylene. Besides the experimental investigations, the tensile properties of the corresponding biocomposites were predicted by using micromechanical analysis. It was shown that considering the same fraction of fibrous materials (pulp fibres vs CNFs), the experimental and modelling results revealed that the highest tensile strength was obtained from the pulp fibre-reinforced biocomposites. Regarding the CNFs-reinforced biocomposites, the compatibilizer content had to be up to 20 wt% to experimentally achieve the tensile strength predicted by the model. © 2023 The Author(s)

  • 19.
    Rouhi, Mohammad S.
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Wysocki, Maciej
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Larsson, Ragnar
    Chalmers University of Technology, Sweden.
    Experimental assessment of dual-scale resin flow-deformation in composites processing2015In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 76, p. 215-223Article in journal (Refereed)
    Abstract [en]

    In this paper we are concerned with the assessment of sub-models within a two-phase continuum mechanical FE framework for process modeling of composites manufacturing. In particular, the framework considers the inclusion of two deformation dependent models describing resin flow related to: (1) meso-scale wetting and compaction of individual plies and (2) overall preform deformation and macroscopic Darcian flow. Using micro-mechanical modeling, we model the physics of these sub-processes in relation to the recently developed Out-Of-Autoclave (OOA) prepergs. The models are placed in context with a compression–relaxation experiment, employed to study the preform deformations considered separated from other sub-processes. Finally, calibrations and model validations are carried out against the relaxation experiment to relate the FE framework to the mechanical response of the preform. Therefore, using the above experiment, parameter values out of the literature and those estimated from micrographs gave a fair agreement between the simulation and experiments.

  • 20.
    Rouhi, Mohammad S.
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Wysocki, Maciej
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP. Chalmers University of Technology, Sweden.
    Larsson, Ragnar
    Chalmers University of Technology, Sweden.
    Modeling of coupled dual-scale flow–deformation processes in composites manufacturing2013In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 46, no 1, p. 108-116Article in journal (Refereed)
    Abstract [en]

    The present contribution is a part of the work towards a framework for holistic modeling of composites manufacturing. Here we focus our attention onto the particular problem of coupled dual-scale deformation–flow process such as the one arising in RTM, Vacuum Assisted Resin Infusion (VARI) and Vacuum Bag Only (VBO) prepregs. The formulation considers coupling effects between macro-scale preform processes and meso-scale ply processes as well as coupling effects between the solid and fluid phases. The framework comprises a nonlinear compressible fiber network saturated with incompressible fluid phase. Internal variables are introduced in terms of solid compressibility to describe the irreversible mesoscopic infiltration and reversible preform compaction processes. As a main result a coupled displacement–pressure, geometrically nonlinear, finite element simulation tool is developed. The paper is concluded with a numerical example, where a relaxation–compression test of a planar fluid filled VBO preform at globally un-drained and partly drained conditions is considered.

  • 21.
    Svanberg, Magnus
    et al.
    RISE, Swerea, Swerea SICOMP.
    Holmberg, Anders
    RISE, Swerea, Swerea SICOMP.
    An experimental investigation on mechanisms for manufacturing induced shape distortions in homogeneous and balanced laminates2001In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 32, no 6, p. 827-838Article in journal (Refereed)
    Abstract [en]

    Manufacturing induced shape distortions is a common problem for composite manufacturers. For single curved geometries the phenomenon is known as spring-in. Today a lot of effort is spent to develop modelling tools for prediction of spring-in and shape distortions in general. However, good experimental data is rare in the literature and there are no established constitutive models capable of account for the effect from different cure schedules. In this paper, experimental data for spring-in of glass-fibre epoxy composites are presented. The experiments were performed with angle brackets manufactured by RTM, in a steel mould with accurate temperature control. Different in-mould temperature have been used to point out and separate different mechanisms responsible for spring-in. © 2001 Elsevier Science Ltd.

  • 22.
    Svanberg, Magnus
    et al.
    RISE, Swerea, Swerea SICOMP.
    Holmberg, Anders
    RISE, Swerea, Swerea SICOMP.
    Prediction of shape distortions Part I. FE-implementation of a path dependent constitutive model2004In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 35, no 6, p. 711-721Article in journal (Refereed)
    Abstract [en]

    There is a great interest, especially from the aircraft industry, to increase the ability to understand and predict development of shape distortions and residual stresses during manufacture of polymer composite components. An increased ability to predict shape distortions will result in more cost efficient development, improved performance and optimised manufacturing of composites. To be able to predict residual stresses and shape distortions a model is needed that accounts for all important mechanisms involved. In a previous work by the authors, it was demonstrated that such - models must account for thermal expansion (different in glassy and rubbery state), chemical shrinkage due to the crosslinking reaction and finally frozen-in deformations. The present paper presents a simple mechanical constitutive model that accounts for the mechanisms mentioned above. The model is a limiting case of linear visco-elasticity that permits us to replace the rate dependence by a path dependence on the state variables: strain, degree of cure and temperature. This means significant savings in computational time, memory requirements and costs for material characterisation as compared to conventional visco-elastic models. This is the first of two papers, the second paper deals with experimental validation and analysis of mechanical boundary conditions during prediction of shape distortion. © 2004 Elsevier Ltd. All rights reserved.

  • 23.
    Svanberg, Magnus
    et al.
    RISE, Swerea, Swerea SICOMP.
    Holmberg, Anders
    RISE, Swerea, Swerea SICOMP.
    Prediction of shape distortions. Part II. Experimental validation and analysis of boundary conditions2004In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 35, no 6, p. 723-734Article in journal (Refereed)
    Abstract [en]

    During cure of thermoset composite structures residual stresses and/or shape distortions are always present. Residual stresses can cause apparent strength reduction or failure, even prior demoulding, respectively, shape distortions can deform a component so that the component becomes useless. For this reason a lot of effort has been spent to develop simulation tools to be able to foresee problems related to residual stresses and/or shape distortions and make the first part right. In a companion paper a process model for shape distortion predictions was developed and implemented into ABAQUS. In the present paper the model is validated for a material and cure schedule typical for RTM and autoclave processes. Comparisons between predicted and experimental shape distortion shows that the model and simulation approach used capture both effects from different cure schedules as well as the mechanical interaction between composite and tooling during in-mould cure. The results show that changing the mechanical boundary conditions significantly affects the shape distortion prediction. Therefore accurate modelling of the composite-tooling interaction is an important part of a shape distortion analysis. © 2004 Elsevier Ltd. All rights reserved.

  • 24.
    Syerko, E.
    et al.
    Nantes Université, France.
    Rouhi, Mohammad
    RISE Research Institutes of Sweden, Materials and Production, Polymeric Materials and Composites. National University of Singapore, Singapore.
    Vorobyev, R
    Skolkovo Institute of Science and Technology, Russia.
    Benchmark exercise on image-based permeability determination of engineering textiles: Microscale predictions2023In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 167, article id 107397Article in journal (Refereed)
    Abstract [en]

    Permeability measurements of engineering textiles exhibit large variability as no standardization method currently exists; numerical permeability prediction is thus an attractive alternative. It has all advantages of virtual material characterization, including the possibility to study the impact of material variability and small-scale parameters. This paper presents the results of an international virtual permeability benchmark, which is a first contribution to permeability predictions for fibrous reinforcements based on real images. In this first stage, the focus was on the microscale computation of fiber bundle permeability. In total 16 participants provided 50 results using different numerical methods, boundary conditions, permeability identification techniques. The scatter of the predicted axial permeability after the elimination of inconsistent results was found to be smaller (14%) than that of the transverse permeability (∼24%). Dominant effects on the permeability were found to be the boundary conditions in tangential direction, number of sub-domains used in the renormalization approach, and the permeability identification technique. 

  • 25.
    Trey, Stacy
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, Trätek.
    Gamstedt, E. Kristofer
    Mäder, Edith
    Jönsson, Sonny
    Johansson, Mats
    Glass fiber reinforced high glass transition temperature thiol–ene networks2011In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 42, no 11, p. 1800-1808Article in journal (Refereed)
  • 26.
    Tsampas, Spyros
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Greenhalgh, E. S.
    Imperial College London, UK.
    Ankersen, J.
    GKN Aerospace CTC, UK.
    Curtis, P. T.
    Physical Sciences Department DSTL, UK.
    Compressive failure of hybrid multidirectional fibre-reinforced composites2015In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 71, p. 40-58Article in journal (Refereed)
    Abstract [en]

    In this paper, the hybridisation of multidirectional carbon fibre-reinforced composites as a means of improving the compressive performance is studied. The aim is to thoroughly investigate how hybridisation influences the laminate behaviour under different compression conditions and thus provide an explanation of the "hybrid effect". The chosen approach was to compare the compressive performance of two monolithic carbon fibre/epoxy systems, CYTEC HTS/MTM44-1 and IMS/MTM44-1, with that of their respective hybrids. This was done by keeping the same layup throughout ((0/90/45/-45)2S) while replacing the angle plies in one case or the orthogonal plies in the other case with the second material, thus producing two hybrid systems. To investigate the compressive performance of these configurations, compact and plain compression test methods were employed which also allowed studying the sensitivity of compressive failure to specimen geometry and loading conditions. The experimental results and the subsequent fractographic analysis revealed that the hybridisation of selective ply interfaces influenced the location and severity of the failure mechanisms. Finally, in light of this knowledge, an update of the generic sequence of events, previously suggested by the authors, which lead to global fracture in multidirectional fibre-reinforced composites under compression is presented. 

  • 27.
    Vernet, Nicolas
    et al.
    Ecole Polytechnique de Montreal, Canada.
    Ruiz, Edu
    Ecole Polytechnique de Montreal, Canada.
    Advani, Suresh G.
    University of Delaware, USA.
    Alms, Justin B.
    University of Delaware, USA.
    Aubert, M.
    Hexcel Reinforcements, France.
    Barburski, Marcin
    KU Leuven, Belgium.
    Barari, Bamdad
    University of Wisconsin, USA.
    Beraud, Jean Marc
    Hexcel Reinforcements, France.
    Berg, David Christian
    Technische Universität Clausthal, Germany.
    Correia, Nuno C.
    Universidade Do Porto, Portugal.
    Danzi, Mario
    Eidgenössische Technische Hochschule Zürich, Switzerland.
    Delaviere, T.
    Ecole Polytechnique Fédérale de Lausanne, Switzerland.
    Dickert, Matthias
    Technische Universität Clausthal, Germany.
    Di Fratta, Claudio
    Eidgenössische Technische Hochschule Zürich, Switzerland.
    Endruweit, Andreas
    University of Nottingham, United Kingdom.
    Ermanni, Paolo A.
    Technische Universität Clausthal, Germany.
    Francucci, Gaston
    National University of Mar Del Plata, Argentina.
    Garcia, J. A.
    Universitat Politecnica de Valencia, Spain.
    George, Andrew R.
    RISE, Swerea, SICOMP.
    Hahn, Christoph
    Technische Universität München, Germany.
    Klunker, Florian
    Eidgenössische Technische Hochschule Zürich, Switzerland.
    Lomov, Stepan Vladimirovitch
    KU Leuven, Belgium.
    Long, Andrew C.
    University of Nottingham, United Kingdom.
    Louis, Bryan Michael
    Eidgenössische Technische Hochschule Zürich, Switzerland.
    Maldonado, Jesus I.
    Eidgenössische Technische Hochschule Zürich, Switzerland.
    Meier, Reinhold
    Technische Universität München, Germany.
    Michaud, Veronique J.
    Eidgenössische Technische Hochschule Zürich, Switzerland.
    Perrin, Henri
    Pole de Plasturgie de l'Est, France.
    Pillai, Krishna M.C.
    University of Wisconsin, USA.
    Rodriguez, Exequiel S.
    National University of Mar Del Plata, Argentina.
    Trochu, Francois
    Ecole Polytechnique de Montreal, Canada.
    Verheyden, S.
    Ecole Polytechnique Federale de Lausanne, Switzerland.
    Weitgrefe, M.
    Pole de Plasturgie de l'Est, France.
    Xiong, W.
    Eidgenössische Technische Hochschule Zürich, Switzerland.
    Zaremba, Swen
    Technische Universität München, Germany.
    Ziegmann, Gerhard
    Technische Universität Clausthal, Germany.
    Experimental determination of the permeability of engineering textiles: Benchmark II2014In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 61, p. 172-184Article in journal (Refereed)
    Abstract [en]

    In this second international permeability benchmark, the in-plane permeability values of a carbon fabric were studied by twelve research groups worldwide. One participant also investigated the deformation of the tested carbon fabric. The aim of this work was to obtain comparable results in order to make a step toward standardization of permeability measurements. Unidirectional injections were thus conducted to determine the unsaturated in-plane permeability tensor of the fabric. Procedures used by participants were specified in the guidelines defined for this benchmark. Participants were asked to use the same values for parameters such as fiber volume fraction, injection pressure and fluid viscosity to minimize sources of scatter. The comparison of the results from each participant was encouraging. The scatter between data obtained while respecting the guidelines was below 25%. However, a higher dispersion was observed when some parameters differed from the recommendations of this exercise.

  • 28.
    Wagih, A.
    et al.
    University of Girona, Spain; Zagazig University, Egypt.
    Maimí, P.
    University of Girona, Spain.
    González, E. V.
    University of Girona, Spain.
    Blanco, N.
    University of Girona, Spain.
    De Aja, J. R. S.
    Aernnova Engineering Solutions Ibérica S.A., Spain.
    De La Escalera, F. M.
    Aernnova Engineering Solutions Ibérica S.A., Spain.
    Olsson, Robin
    RISE, Swerea, SICOMP.
    Alvarez, E.
    Oxeon AB, Sweden.
    Damage sequence in thin-ply composite laminates under out-of-plane loading2016In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 87, p. 66-77Article in journal (Refereed)
    Abstract [en]

    The study of the damage sequence in polymer-based composite laminates during an impact event is a difficult issue. The problem can be more complex when the plies are thin. In this paper, quasi-static indentation tests were conducted on thin-ply laminates to understand qualitatively the damage mechanisms and their sequence during low-velocity impact loading. TeXtreme® plain weave plies were used with two different thicknesses, 0.08 mm and 0.16 mm (referenced as ultra-thin-ply and thin-ply, respectively), and tested under different load levels. Load-displacement curves were analyzed and the extent of damage was inspected using optical microscopy and ultrasonic technique. The results showed that the damage onset occurs earlier in thin-ply laminates. The damage onset in thin-ply laminates is matrix cracking which induces delaminations, whereas for ultra-thin-ply laminates is due to delaminations which are induced by shear forces and small amount of matrix cracking. Moreover, the fiber breakage appears earlier in ultra-thin-ply laminates.

  • 29.
    Wilhelmsson, D
    et al.
    Chalmers University of Technology, Sweden.
    Gutkin, Renaud
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Edgren, F
    GKN Aerospace Sweden AB, Sweden.
    Asp, L E
    Chalmers University of Technology, Sweden.
    An experimental study of fibre waviness and its effects on compressive properties of unidirectional NCF composites2018In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 107, p. 665-674Article in journal (Refereed)
    Abstract [en]

    In this paper a comprehensive experimental study on effects of different fibre waviness characteristics on the compressive properties of unidirectional non-crimp fabrics (NCF) composites is presented. The fibre waviness ranges from periodic to random with medium to large misalignment angles. As expected, fibre waviness is found to strongly impair the compressive mechanical properties of the composite. It is demonstrated that the maximum fibre misalignment alone can be used to accurately predict strength with analytical kinking criteria. Furthermore, there is a direct correlation between waviness and a knock-down factor on stiffness with approximately 5%/degree mean fibre misalignment angle. Analysis of the extension of the misaligned regions (defects) provides additional evidence that defect extension in the transverse direction is more critical than in the longitudinal direction, supporting earlier theoretical predictions in the open literature.

  • 30.
    Wysocki, Maciej
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Toll, S.
    KTH Royal Institute of Technology.
    Larsson, R.
    Chalmers University of Technology.
    Asp, Leif
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    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. © 2009 Elsevier Ltd. All rights reserved.

  • 31.
    Zarna, Chiara
    et al.
    NTNU, Norway.
    Chinga-Carrasco, Gary
    RISE Research Institutes of Sweden, Bioeconomy and Health, Material and Surface Design.
    Echtermeyer, Andreas T
    NTNU, Norway.
    Bending properties and numerical modelling of cellular panels manufactured from wood fibre/PLA biocomposite by 3D printing2023In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 165, article id 107368Article in journal (Refereed)
    Abstract [en]

    The major advantage of cellular structures is the saving of material, energy, cost, and weight. Biocomposites are strong, lightweight materials and offer a high degree of design freedom. The purpose of this study was to characterise and compare the bending properties of various cellular structures for utilisation in panels made of a wood fibre/PLA biocomposite. Material extrusion (MEX) 3D printing is a highly flexible manufacturing method and well-suited for prototyping. Hence, MEX was applied to manufacture five different cell configurations that were mechanically tested. Additionally, numerical simulations were carried out to present a tool for optimising the structures for future requirements. Two material modelling approaches, a hyperelastic and a linear elastic, bimodular model were created and validated based on 3-point-bending tests. It is shown that a linear elastic, bimodular and perfectly plastic material model can adequately capture the elastic/plastic bending behaviour of the corresponding 3D-printed sandwich panels. © 2022 The Author(s)

  • 32.
    Zhuang, Linqi
    et al.
    Texas A&M University, USA; Luleå University of Technology, Sweden.
    Pupurs, Andrejs
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP. Luleå University of Technology, Sweden.
    Varna, Janis
    Luleå University of Technology, Sweden.
    Talreja, Ramesh
    Texas A&M University, USA ; Luleå University of Technology, Sweden.
    Ayadi, Zoubir
    University of Lorraine, France.
    Effects of inter-fiber spacing on fiber-matrix debond crack growth in unidirectional composites under transverse loading2018In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 109, p. 463-471Article in journal (Refereed)
    Abstract [en]

    The energy release rate (ERR) of a fiber–matrix debond crack in a unidirectional composite subjected to transverse tension is studied numerically. The focus of the study is the effect of the proximity of the neighboring fibers on the ERR. For this, a hexagonal pattern of fibers in the composite cross-section is considered. Assuming one fiber to be debonded at certain initial debond arc-length, the effect of the closeness of the surrounding six fibers on the ERR of the crack is studied with the inter-fiber distance as a parameter. Using an embedded cell consisting of discrete fibers in a matrix surrounded by the homogenized composite, a finite element model and the virtual crack closure technique are used to calculate the ERR. Results show that the presence of the local fiber cluster accelerates the crack growth up to a certain initial crack angle, beyond which the opposite effect occurs. It is also found that the residual stress due to thermal cooldown reduces the ERR. However, the thermal cooldown is found to enhance the debond growth in plies within a cross-ply laminate.

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