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  • 51.
    Edgren, Fredrik
    RISE, Swerea, Swerea SICOMP.
    Hälso- och säkerhetsrisker med kolfiber-epoxi komposit2006Report (Refereed)
  • 52.
    Edgren, Fredrik
    RISE, Swerea, Swerea SICOMP.
    Progressive damage and failure models for composite materials in ABAQUS2007Report (Refereed)
  • 53.
    Edgren, Fredrik
    RISE, Swerea, Swerea SICOMP.
    Using cohesive interface elements to compare different ply drop-off strategies2007Report (Refereed)
  • 54.
    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.

  • 55.
    Edgren, Fredrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Asp, Leif
    RISE, Swerea, Swerea SICOMP.
    Bull, P.H.
    Royal Institute of Technology.
    Compressive failure of impacted NCF composite sandwich panels - Characterisation of the failure process2004In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 38, no 6, p. 495-514Article in journal (Refereed)
    Abstract [en]

    In the present study, non-crimp fabric (NCF) composite face sheet sandwich panels have been tested in compression after impact (CAI). Damage in the face sheets was characterised by fractography. Compression after impact loaded panels were found to fail by plastic fibre microbuckling (kinking) in the damaged face sheet. Studies of panels for which loading was interrupted prior to failure revealed extensive stable kink band formation at several positions and in numerous plies. Kink bands initiated and propagated within a wide region close to the point of impact. In addition, kink bands initiated in zones with high shear stresses, away from the impact centre line. Consequently, the fractographic results from this investigation do not support the assumption of modelling the impact damage as an equivalent hole. To achieve accurate predictions of kink band initiation, the stress field must be known. The results from this study imply that bending effects caused by remaining dent or material eccentricities in the damaged region must be considered.

  • 56.
    Edgren, Fredrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Asp, Leif
    RISE, Swerea, Swerea SICOMP.
    Joffe, Roberts
    RISE, Swerea, Swerea SICOMP.
    Failure of NCF composites subjected to combined compression and shear loading2006In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 66, no 15, p. 2865-2877Article in journal (Refereed)
    Abstract [en]

    Earlier studies have shown that formation of kink bands is the mechanism that is likely to govern failure of compression loaded non-crimp fabric (NCF) composite laminates. Because of this, a failure criterion for prediction of failure caused by kinking under multiaxial (axial compression and shear) loading has been adapted to a NCF composite system. The criterion has been validated for compression tests of quasi-isotropic laminates tested in uniaxial compression. By performing compression tests of the laminate at different off-axis angles, it was possible to vary the ratio of compressive axial stress/shear stress in the specimens. The test results proved that the criterion works well for predictions of kinking governed failure for the present material system. Detailed fractographic studies confirmed that formation of kink bands was the mechanism responsible for specimen failure. Kink bands were also found to develop at loads significantly lower than load at specimen failure. © 2006 Elsevier Ltd. All rights reserved.

  • 57.
    Edgren, FRedrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Mattsson, D.
    Luleå University of Technology.
    Asp, Leif
    RISE, Swerea, Swerea SICOMP.
    Varna, J.
    Luleå University of Technology.
    Formation of damage and its effects on non-crimp fabric reinforced composites loaded in tension2004In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 64, no 5, p. 675-692Article in journal (Refereed)
    Abstract [en]

    Non-crimp fabric (NCF) composites, manufactured by resin infusion techniques are one of the most promising next generation composite materials. They offer large potential for application in primary structures as they give excellent performance at low production costs. However, before NCF composites will be efficiently used in design, detailed understanding of governing micro mechanisms must be accumulated and described by predictive models. In the present study, NCF cross-ply laminates have been tested in tension. Intralaminar cracks caused in the 90° fibre bundle layers and their effect on laminate mechanical properties have been monitored. Occurrence of 'novel' type of cracks propagating in the load direction (longitudinal cracks) is explained by a thorough FE analysis using an Representative Volume Element (RVE) approach, revealing stress concentrations caused by 0° fibre bundle waviness. Effects of damage on mechanical properties are modelled using modified micro mechanical models developed for analysis of conventional laminated composites. The analysis reveals mechanical degradation to be ruled by the crack opening displacement (COD). However, unlike traditional composites, transverse cracks do not generally extend through the entire thickness of the 90° layer, but are rather contained in single fibre bundles, limiting the COD. © 2003 Elsevier Ltd. All rights reserved.

  • 58.
    Edgren, Fredrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Soutis, C.
    The University of Sheffield.
    Asp, Leif
    RISE, Swerea, Swerea SICOMP.
    Damage tolerance analysis of NCF composite sandwich panels2008In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 68, no 13, p. 2635-2645Article in journal (Refereed)
    Abstract [en]

    This paper concerns development and validation of impact damage representations in carbon fibre non-crimp fabric reinforced face sheets for damage tolerance analysis of sandwich panels loaded in compression. For this purpose, experimental data accompanied by fractographic observations have been employed to scrutinize numerical predictions by state-of-the-art notch strength models. As a result, equivalent hole representations of visible impact damage (VID) and, more surprisingly, of the subtle barely visible impact damage (BVID) are recommended for reliable damage tolerance prediction of the compression after impact (CAI) load case for the investigated panels. This recommendation relies on the identification of the mechanisms controlling failure resulting in reliable damage tolerance predictions employing a linear cohesive zone model. © 2008 Elsevier Ltd. All rights reserved.

  • 59.
    Ekstedt, Sofia
    RISE, Swerea, Swerea SICOMP.
    Analysis of composite materials lay-up and materials2009Report (Refereed)
  • 60.
    Ekstedt, Sofia
    RISE, Swerea, Swerea SICOMP.
    Carbon Fibre Material structure and electrical properties2008Report (Refereed)
  • 61.
    Ekstedt, Sofia
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Wysocki, Maciej
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Asp, Leif
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Structural batteries made from fibre reinforced composites2009Conference paper (Refereed)
    Abstract [en]

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

  • 62.
    Ekstedt, Sofia
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Wysocki, Maciej
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Asp, Leif
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Structural batteries made from fibre reinforced composites2010Conference paper (Refereed)
    Abstract [en]

    Structural, fibre reinforced, battery prototypes with two types of electrolyte matrix material (a gel and a solid polymer) have been manufactured. This was to confirm the concept of using carbon fibres as current collector in the anode as well as providing a mechanical load-carrying functionality. As a result, functioning batteries with gel electrolyte have been produced and their properties have been characterised. © 2010 Maney Publishing.

  • 63.
    Emami, Nazanin
    RISE, Swerea, Swerea SICOMP.
    Rheology during curing of unsaturated polyester and ATH suspensions2005Report (Refereed)
  • 64.
    Engström, Jonas
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Calculated data for thermoset and glass fibre composite material in FACOMP2009Report (Refereed)
  • 65.
    Engström, Jonas
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Joffe, Roberts
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Fernberg, Patrik
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Characterization of carbon nanotube doped carbon fiber prepreg laminate2012Conference paper (Refereed)
    Abstract [en]

    The current paper reports results from a preliminary study on PREGCYL™ NC R2HM-01 which is a carbon nanotube doped prepreg produced by Nanocyl. The work consisted of sample manufacturing in autoclave, microcopy analysis with XHR-SEM and mechanical testing. The mechanical testing consisted of tensile tests of unidirectional (in longitudinal direction) and cross-ply laminates. Test of unidirectional laminates showed that stiffness of the PREGCYL material is slightly higher than that of MTM55 composites (111GPa vs 102GPa). The results from tests of cross-ply laminates indicated that damage (transverse cracks) initiation is delayed in PREGCYL composites compare to the MTM55 material. Damage accumulation also seems to be slower in nano-doped composites.

  • 66.
    Farajzadeh Khosroshahi, S.
    et al.
    University of Padova, Italy.
    Olsson, Robin
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Wysocki, Maciej
    RISE - Research Institutes of Sweden, Bioscience and Materials, Chemistry and Materials.
    Zaccariotto, M.
    University of Padova, Italy.
    Galvanetto, U.
    University of Padova, Italy.
    Response of a helmet liner under biaxial loading2018In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 72, p. 110-114Article in journal (Refereed)
    Abstract [en]

    Helmets are the most effective protective item for motorcyclists. The liner of the helmet is the part of the helmet which dissipates most of the impact energy and mitigates the risk of head injuries. It has been proposed that the helmet test standards should include assessment of the helmets for oblique impacts that is not currently addressed in the standards. A conventional uniaxial compression test method is still used for characterization of the helmet liner material. However, compressive tests of EPS foams provide reliable results for normal loading on EPS, but do not provide a realistic result for oblique impacts. Therefore, we carried out experimental tests to measure the response of EPS foams, which are commonly used for helmet liners, under biaxial loading. The result of our experiments show that the shear response of EPS foams is a function of axial compression, and increasing the axial strain leads to increased shear stiffness, and thus higher levels of shear stress. We also showed that including shear-stiffening of EPS in the FE assessment of helmets may change the headform rotational acceleration by 25%. Therefore, such behavior of EPS foams should be included in FE analysis of helmets in the case of oblique impacts for a more realistic assessment of their performance.

  • 67.
    Fernberg, Patrik
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    Gong, Guan
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Mannberg, Peter
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Processing and properties of new polyimide composites with high temperature ability2014Conference paper (Refereed)
    Abstract [en]

    The communication present results from work on development and evaluation of new polymeric carbon fiber composites with extreme temperature performance: Tg up to 360°C is targeted. The anticipated use of such composites is found in aeroengine-applications. In the work we are exploring a new and tailored phenyl ethynyl terminated imide (PETI) formulation, specially developed for the program. The formulation utilizes crosslinkers of the Nexamide" type (from Nexam Chemical AB, Sweden). The resins are initially evaluated from a processing and property perspective. Both DSC-measurements and rheology characterization are utilized in the development. Suitable RTM-processing schemes are investigated from a viscosity point of view. The schemes are used in the composite sample manufacturing. Besides a processing perspective the study also present the first results on physical behavior of the polymers and their composites.

  • 68.
    Fernberg, Patrik
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    Gong, Guan
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Mannberg, Peter
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Tsampas, Spyros
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Development of novel high Tg polyimide-based composites. Part I: RTM processing properties2018In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 52, no 2, p. 253-260Article in journal (Refereed)
    Abstract [en]

    In this study, an assessment of the composite processing-related properties of a newly developed 6-FDA-based phenylethynyl-terminated polyimide (available under the tradename NEXIMID®MHT-R) is presented. Processing schemes, used for preparing high quality carbon fibre-reinforced composites by the use of conventional resin transfer moulding are developed and presented. The influences of manufacturing parameters on glass transition temperature of the composites are presented. The results confirm that composites with exceptionally high Tg, in the range between 350 and 460℃ can be achieved. A manufacturing scheme that yields in composites with Tg of 370℃ is presented and proposed as a good candidate to serve as baseline for further studies.

  • 69.
    Fernberg, Patrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Jekabsons, N.
    Luleå University of Technology.
    Determination of bridging laws for SMC materials from DENT tests2003In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 63, no 15, p. 2143-2153Article in journal (Refereed)
    Abstract [en]

    A bridging law (or cohesive zone law) approach is employed to evaluate the fracture of double edge notched tensile (DENT) specimen from two SMC materials (Std-SMC and Flex-SMC) with considerable difference in fracture characteristics. Linear- and non-linear FEM was used to separate volumetric body contributions and true crack opening from measured displacements (measured with extensometer) over the cracked region. We found that extrinsic non-linear material response gave a significant contribution to measured displacements. The paper also considers the influence of specimen dimensions on the characteristics of fracture. This is of great importance since stable crack growth is required in order to allow a complete determination of the bridging law in a single experiment. By applying corrections for volumetric displacements in the data reduction scheme we were able to estimate the bridging laws of the two SMCs respectively. They were found to be of decreasing nature and two distinct regions were identified. For small δ, a steeply decreasing part where debonding and fiber fracture are major micro-scale failure mechanism, is identified. At larger δ, a transition to a less steep bridging law response is observed. Pullout friction governs the bridging law at that stage. © 2003 Elsevier Ltd. All rights reserved.

  • 70.
    Fernberg, Patrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Joffe, Roberts
    RISE, Swerea, Swerea SICOMP.
    Edgren, F.
    Volvo Aero Corporation.
    Carbon nanotube treated carbon fibre preforms for improved properties of aeronautical grade composites2012In: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite MaterialsConference paper (Refereed)
    Abstract [en]

    The current paper reports work on development of enhanced carbon fibre composites manufactured by resin transfer moulding (RTM). In particular, the possibility to obtain a toughened composite through deposition of carbon nanotubes (CNT) on the fibres is investigated. The hypothesis is that deposition of CNT on the fibre surface has two major advantages: a) filtering problems during manufacturing are eliminated and b) CNT can contribute to a local toughening in the vicinity of fibres, where stress concentrations often are high. Unidirectional and multi-axial composites, with and without CNT-modification, were manufactured using conventional RTM-technique and HexFlow®RTM6 epoxy resin. The composites were characterized by means of mechanical testing (interlaminar shear strength, ILSS) and microscopy. Significant improvements by 13 to37 % in ILSS values were achieved with the addition of CNT. Stiffness degradation tests were also performed. The results from these tests were not completely conclusive. Some treatments promoted stiffness degradation whereas others had no apparent effect.

  • 71.
    Fernberg, Patrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Joffe, Roberts
    RISE, Swerea, Swerea SICOMP.
    Nilsson, Greger
    RISE, Swerea, Swerea SICOMP.
    Strain and damage sensing during loading of carbon nanotube doped composites2009In: ICCM International Conferences on Composite MaterialsConference paper (Refereed)
    Abstract [en]

    This work explores the possibility to use resistance changes in a carbon nanotube (CNT) doped composites to monitor deformations and damage. Most other studies in the field are done on simplified uniaxial loading whereas current work also evaluates the possibilities to monitor strain in more complex loading case, such as bending.

  • 72.
    Fernberg, Patrik
    et al.
    RISE, Swerea, SICOMP. Luleå University of Technology, Sweden.
    Joffe, Roberts
    RISE, Swerea, SICOMP. Luleå University of Technology, Sweden.
    Tsampas, Spyros
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Mannberg, Peter
    RISE, Swerea, SICOMP.
    Influence of post-cure on carbon fibre polyimide composites with glass transition temperatures above 400c2015In: ICCM International Conferences on Composite Materials, International Committee on Composite Materials , 2015Conference paper (Refereed)
    Abstract [en]

    The current communication present results from work on polymeric composites with extreme temperature performance. This study focuses on carbon fibre composites based on a new phenyl ethynyl terminated polyimide formulation NEXIMID® MHT-R (Nexam Chemicals AB, Sweden) based on hexafluoroisopropylidene bisphthalic dianhydride (6-FDA), 4-(Phenylethynyl)Phthalic Anhydride (4-PEPA) and ethynyl bis-phthalic anhydride (EBPA). In particular influence of post-cure conditions such as time, temperature and atmosphere on Tg of the composites is investigated. In addition to this monitoring and analyses of the consequences of post-cure on mass loss and occurrence of micro-cracks is carried out. Three different post-curing temperatures are considered in this study: 400°C, 420°C and 440°C. Two different atmospheres, air and inert by nitrogen, were also investigated. In summary the results reveal that remarkably high Tg, up to around 460°C, is achieved with only very limited mass loss. It was also observed that some, but limited amounts of, micro-cracks are developed within the laminates due to the inevitable high thermal stresses generated upon cooling from cure temperature.

  • 73.
    Fernberg, Patrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Nilsson, Greger
    RISE, Swerea, Swerea SICOMP.
    Joffe, R.
    Luleå University of Technology.
    Piezoresistive performance of long-fiber composites with carbon nanotube doped matrix2009In: Journal of Intelligent Materials Systems and Structures, ISSN 1045-389X, E-ISSN 1530-8138, Vol. 20, no 9, p. 1017-1023Conference paper (Refereed)
    Abstract [en]

    The electrical and mechanical properties of carbon nanotube (CNT) doped epoxy resin and composites based on this matrix were studied. The investigation was carried out on neat nanocomposites and on structural composites i.e., when the nanocomposite is used as matrix in composite materials reinforced with long continuous fibers. Tensile tests showed that CNT doped epoxy exhibited clear piezoresistive behavior. It was, however, also shown that geometrical changes of the specimen also contribute significantly to resistance changes during tensile loading. Particular effort was made to establish the relations between transverse cracking in glass fiber cross-ply laminates with nanotube doped matrix and changes of electrical resistance. It was shown that changes of electrical resistance during tensile loading of composites containing CNT doped matrix gives highly relevant information about the damage state of the material. In an unloaded state the resistance change is proportional to the relative change of stiffness. This work demonstrates that there are three different mechanisms, which contribute to changes of electrical resistance of a composite specimen subjected to tensile strain. These three mechanisms are: (a) geometrical changes of the specimen (b) piezoresistive material response, and (c) accumulation of micro-damage. © 2009 SAGE Publications.

  • 74.
    Fernberg, Patrik
    et al.
    RISE, Swerea, Swerea SICOMP.
    Sandlund, Erik
    RISE, Swerea, Swerea SICOMP.
    Lundström, T.S.
    Luleå University of Technology.
    Mechanisms controlling particle distribution in infusion molded composites2006In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 25, no 1, p. 59-70Article in journal (Refereed)
    Abstract [en]

    This article presents results from an experimental investigation in which two grades of aluminatrihydroxide (ATH) particles are added to liquid resin and used in infusion molding experiments. Based on the results, potential key mechanisms controlling resin flow and hence also the final particle distribution are proposed. A pore doublet model is proposed to explain the seemingly random spatial distribution of particle-dense regions within the final material. These dense regions are found within flow channels, at locations where local shear strain rates are low. This suggests that they are formed as a consequence of a Bingham type of viscosity behavior observed for the suspension and/or due to filtering of particles during fiber bundle impregnation. © 2006 SAGE Publications.

  • 75.
    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.

  • 76.
    George, Andy
    et al.
    RISE, Swerea, Swerea SICOMP.
    Ahlborn, H.
    University of Stuttgart.
    ElGhareeb, M.
    University of Stuttgart.
    Drechsler, K.
    University of Stuttgart.
    Heider, D.
    University of Delaware.
    Compressibility modeling and validation for coupled flow simulation2011In: ICCM International Conferences on Composite MaterialsConference paper (Refereed)
  • 77.
    George, Andy
    et al.
    RISE, Swerea, Swerea SICOMP.
    Drechsler, K.
    Institute of Aircraft Design, Stuttgart.
    Sweden,
    Void characterization and membrane selection in the Vacuum Assisted Process2012In: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite MaterialsConference paper (Refereed)
    Abstract [en]

    The Vacuum Assisted Process (VAP) can achieve better laminate quality than other infusion processes. This study aims to develop void characterization tools, to characterize the resultant void content in VAP, and to evaluate various membranes with respect to laminate quality. Infusions were made with each membrane and either single- or double-sided distribution media coverage. Each laminate's thickness gradient was measured, as well as the void content by three methods for comparison. The voids' position and size were characterized. The ultrasound attenuation and the shear strength were correlated to the local void content.

  • 78.
    George, A.R.
    et al.
    University of Stuttgart.
    Drechsler, K.
    University of Stuttgart.
    Holmberg, A.
    RISE, Swerea, Swerea SICOMP.
    The permeability of tackified, stitched, and braided carbon fiber textiles: Experimental characterization and design modeling2009In: International SAMPE Symposium and Exhibition (Proceedings), ISSN 8910138, Vol. 54Conference paper (Refereed)
    Abstract [en]

    Liquid composite molding (LCM) has greatly benefited from advances in textile preforming. Large and complex part-shapes can be assembled and held in place until resin injection and curing. The three most common preform stabilization techniques are tackification (binders), stitching, and braiding. The often complex geometrical arrangement and inhomogeneous and anisotropic nature of these textile preforms has complicated attempts to model the processing and final properties of such materials, thus hindering their applicability. This paper focuses on the experimental characterization of the permeability of advanced carbon fiber textile preforms. Permeability knowledge allows the simulation of resin flow during processing in LCM. The inplane permeability is determined by the multiple cavity parallel flow technique. Non-crimped fabric (NCF) with various configurations and binder amounts, tailored fiber-placement (TFP) stitched fabric in a variety of orientations, and both biax and triax braided samples are characterized. Previous literature includes measurements of glass-fiber based preforms, and simple carbon weaves and NCF's. But no permeability data has been published for these particular state-of-the-art materials. Strategies to model the design of a preform using similar materials are also presented.

  • 79.
    Giannadakis, K.
    et al.
    Luleå University of Technology.
    Szpieg, Magdalena
    RISE, Swerea, Swerea SICOMP.
    Varna, J.
    Mechanical Performance of a Recycled Carbon Fibre/PP Composite2011In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 51, no 5, p. 767-777Article in journal (Refereed)
    Abstract [en]

    A composite made of recycled carbon fibres in recycled polypropylene matrix is studied experimentally to describe the features of the elastic and time dependent nonlinear mechanical behaviour. The properties of the developed material have a large variability to be addressed and understood. It was found that the stress-strain curves in tension are rather nonlinear at low strain rate and the strength is sensitive to strain rate. The elastic properties' reduction for this composite after loading to high strains is rather limited. More important is that even in the "elastic region" due to viscoelastic effects the slope of loading-unloading curve is not the same and that at higher stress large viscoplastic strains develop and creep rupture is typical. The time and stress dependence of viscoplastic strains was analysed and described theoretically. The viscoelastic response of the composite was analysed using creep compliance, which was found to be slightly nonlinear. © 2010 Society for Experimental Mechanics.

  • 80.
    Gong, Guan
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Literature study of graphene modified polymeric composites2018Report (Other academic)
    Abstract [en]

    This study presents a survey of literatures including recent work in relevant projects, ongraphene modified polymeric composites with a particular focus on fibre reinforcedpolymeric composites.A variety of routes that are used and can potentially be used to integrate graphene intocomposites are reviewed, including dispersing graphene into a polymer matrix, dopinggraphene onto fibre reinforcement, graphene modified prepreg and the use of graphenebuckypaper. The effect of processing parameters, such as dispersion and doping methods,temperature, pressure, etc., along with modification of graphene, on the structure andmechanical, electrical, thermal, barrier, rheological and crystalline properties of the resultantcomposites are also reviewed.The most prominent influencing factors are the intrinsic properties of graphene includingaspect ratio of nanoplatelets and surface functionalization, dispersion and exfoliation as wellas orientation and alignment of graphene, and interactions of graphene-polymer andgraphene-fibre reinforcement. The selection of processing techniques and tailoring ofinfluencing factors depend on the required properties. For instance, deposited graphene ontofibres for reinforcement can be more efficient than dispersed graphene into the polymer toimprove the interfacial and interlaminar properties. Well-dispersed and randomly orientedgraphene can be more beneficial than well-dispersed and aligned graphene for higherelectrical conductivity while less favoured for higher mechanical properties. Potentialapplications of graphene modified polymeric composites addressing industrial and societalchallenges are also discussed.

  • 81.
    Gong, Guan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Nyström, Birgitha
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Joffe, Roberts
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Development of polyethylene/nanoclay masterbatch for use in wood-plastic composites2013Conference paper (Refereed)
    Abstract [en]

    In this work, organoclay reinforced high density polyethylene (HDPE) nanocomposites were prepared at laboratory scale using a batch mixer. Processing conditions, maleic anhydride modified polyethylene (MAPE) type and MAPE/clay weight ratio were optimised. The microstructure of the resultant nanocomposites was analysed by X-ray diffraction and melt rheology tests, and flexural properties and thermal stability were evaluated. Three types of MAPEs with different melt flow indices (MFI) and maleic anhydride contents all improved the interaction between HDPE and clay and promoted clay dispersion. Nanocomposites where the MAPE with MFI most similar to HDPE was used showed the best exfoliation of clay and the strongest HDPE/clay interface. Mechanical properties were slightly improved, while thermal stability was distinctly enhanced in these HDPE nanocomposites compared with neat HDPE and HDPE nanocomposite without MAPE. The prepared HDPE nanocomposites show the potential to improve the thermal stability of wood-plastic composites for structural applications. © 2013 Institute of Materials, Minerals and Mining.

  • 82.
    Gong, Guan
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Nyström, Birgitha
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Joffe, Roberts
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP. Luleå Univerity of Technology, Sweden.
    Enhanced thermal stability and flame retarding properties of recycled polyethylene based wood composites via addition of polyethylene/nanoclay masterbatch2013In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 42, no 6, p. 244-255Article in journal (Refereed)
    Abstract [en]

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

  • 83.
    Gong, Guan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Nyström, Birgitha
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Sandlund, Erik
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Eklund, Daniel
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Noel, Maxime
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Westerlund, Robert
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Stenberg, Sofia
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Pupure, Liva
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    Pupurs, Andrejs
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    Joffe, Roberts
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    Development of electrophoretic deposition prototype for continuous production of carbon nanotube-modified carbon fiber fabrics used in high-performance multifunctional composites2018In: Fibers, ISSN 2079-6439, Vol. 6, no 4, article id 71Article in journal (Refereed)
    Abstract [en]

    An electrophoretic deposition (EPD) prototype was developed aiming at the continuous production of carbon nanotube (CNT) deposited carbon fiber fabric. Such multi-scale reinforcement was used to manufacture carbon fiber-reinforced polymer (CFRP) composites. The overall objective was to improve the mechanical performance and functionalities of CFRP composites. In the current study, the design concept and practical limit of the continuous EPD prototype, as well as the flexural strength and interlaminar shear strength, were the focus. Initial mechanical tests showed that the flexural stiffness and strength of composites with the developed reinforcement were significantly reduced with respect to the composites with pristine reinforcement. However, optical microscopy study revealed that geometrical imperfections, such as waviness and misalignment, had been introduced into the reinforcement fibers and/or bundles when being pulled through the EPD bath, collected on a roll, and dried. These defects are likely to partly or completely shadow any enhancement of the mechanical properties due to the CNT deposit. In order to eliminate the effect of the discovered defects, the pristine reinforcement was subjected to the same EPD treatment, but without the addition of CNT in the EPD bath. When compared with such water-treated reinforcement, the CNT-deposited reinforcement clearly showed a positive effect on the flexural properties and interlaminar shear strength of the composites. It was also discovered that CNTs agglomerate with time under the electric field due to the change of ionic density, which is possibly due to the electrolysis of water (for carboxylated CNT aqueous suspension without surfactant) or the deposition of ionic surfactant along with CNT deposition (for non-functionalized CNT aqueous suspension with surfactant). Currently, this sets time limits for the continuous deposition.

  • 84.
    Gong, Guan
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Nyström, Birgitha
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Sandlund, Erik
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Eklund, Danierl
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Noel, Maxime
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Westerlund, Robert
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Joffe, Roberts
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    Pupure, Liva
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    Pupurs, Andrejs
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP. Luleå University of Technology, Sweden.
    SCALING-UP PRODUCTION OF CNT-COATEDFIBRE REINFORCEMENT USING CONTINUOUS EPDFOR HIGH-PERFORMANCE ANDMULTIFUNCTIONAL COMPOSITES2018Conference paper (Refereed)
    Abstract [en]

    Itis important within the composite community to improve out-of-plane performance ofcomposites dominated by polymer matrix and properties of matrix-rich regions formed in the gapsbetween the interlaced fibre bundles. These properties are difficult to modify with traditional fibrereinforcement. Various nanoscale materials have been explored for such purpose, among which carbonnanotube (CNT) has been suggested as an ideal candidate because of its outstanding mechanical,electrical and thermal properties (1). Electrophoretic deposition (EPD) is considered as a cost-effectivemethod to deposit CNTs onto substrates with mild working conditions, requiring relatively simpleequipment and being amenable to scaling up (2,3). Due to the shortcoming of existing laboratory setupwhich corresponds to a non-continuous process, EPD has not been used at even a pilot plant scale fornano-coated fibre reinforcement. The current work presents the development of a prototype andmethod for continuous EPD process. Geometric defect of fibre reinforcement introduced during thedeposition, which can shadow the reinforcing effect of CNT deposit, was discovered. Enhancement ofcomposite properties by the CNT deposit was hence shown.

  • 85.
    Gonga, Guan
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP.
    Li, Bin
    Wichita State University, USA.
    Dielectric properties of bionanocomposites2017In: Polymer Nanocomposites for Dielectrics, Pan Stanford Publishing Pte. Ltd. , 2017, p. 139-169Chapter in book (Other academic)
    Abstract [en]

    Bionanocomposites represent an emerging group of nanostructured hybrid materials. Besides the structural and functional properties similar to conventional nanocomposites, the inherent properties, namely, biocompatibility and biodegradability, make these environmentally benign materials highly attractive for both academia and industry. Research on bionanocomposites is an interdisciplinary field that is closely related to packaging and biological systems, such as tissue engineering and drug delivery, and also extended to electronics, sensor, and energy applications, just to name a few. This chapter will give an overview on the research progress of self-assembled bionanocomposites and artificial nanocomposites composed of typical biopolymers and nanoparticles, which exhibit dielectric functions and can have promising potential to be used in biological, electronic, and energy storage applications. 7.1 IntroductionDwindling fossil resources and growing environmental concerns have led to increasing need for sustainable solutions. Overdependence on petroleum resources and environmental impact/carbon footprint can be alleviated by biomaterials development using biological resources or more precisely annually renewable resources. Bionanocomposites are formed by the polymer matrix and reinforcing phase, either of them or both based on renewable resources, and show at least one dimension on the nanometer scale. Bionanocomposites have been the subject of extensive research since the last two decades. These efforts have generated environment-friendly applications for many uses, such as for automotive, packaging, and household products, to name some [1]. Multifunctionality is a trend of development to expand the applications of bionanocomposites.Dielectric bionanocomposites can be utilized for various applications such as conductive elements, heating devices, electromagnetic interference, supercapacitor, shielding and antimicrobial elements, and bio-applications like those of tissue scaffolds for the replacement or restoration of damaged or malfunctioning tissue because a variety of tissue respond to electrical stimulation [2]. On the other hand, an accurate and comprehensive description of structures is of vital importance for the development of high-quality bionanocomposites, which is, however, very difficult because of their nature. Electrical conductivity depends on the micro-and macroscopic states of the composites and gives information on the interaction of individual components inside. Determining the electrical properties of a material is therefore one of the most convenient and sensitive methods for studying the structures of materials [3, 4]. The dielectric properties of bionanocomposites depend on the nature of biopolymer matrix and filler particles, the dimension (mainly include length-to-diameter or aspect ratio) and content of filler particles, and the interfacial characteristics. These issues are taken into consideration in this chapter when reviewing the dielectric performance of bionanocomposites. © 2017 by Pan Stanford Publishing Pte. Ltd.

  • 86.
    Grammatikos, Sotirios A.
    et al.
    Norwegian University of Science and Technology, Norway.
    Tsampas, Spyros Anastasios
    GKN Aerospace Engine Systems, Sweden.
    Pettersson, Jocke
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP. RISE Research Institutes of Sweden, Materials and Production, Polymeric Materials and Composites.
    Luping, Tang
    Chalmers University of Technology, Sweden.
    Löfgren, Ingemar
    Thomas Concrete Group AB, Sweden.
    Recycling and re-purposing decommisioned construction polymer composites for construction applications2018In: ECCM 2018 - 18th European Conference on Composite Materials, Applied Mechanics Laboratory , 2018Conference paper (Refereed)
    Abstract [en]

    Fibre reinforced polymer composites (FRPs) are being increasingly used in aerospace and automotive applications due to their high specific mechanical properties. The construction industry has also started taking advantage of the potential of FRPs for both structural and non-structural purposes. The result of this remarkable absorption of FRPs within the worldwide production market, has led to an immense increase of decommissioned thermoset-matrix components. Nowadays, the majority of the decommissioned FRP components are recovered energy-wise through incineration or simply discarded in landfills around the globe. Within the framework of this paper, we present a solution for the extension of the service life of decommissioned FRP components. Decommissioned electrical insulation FRP pipes were granulated and incorporated as fillers within both cementitious and polymer matrix composites. The effect of FRP granulates on the mechanical performance of cementitious and polymer matrix composites is examined to determine the maximum granulate-filler fraction that can be recycled without compromising the mechanical performance and manufacturing process.

  • 87.
    Grauers, Lisa
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Olsson, Robin
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Gutkin, Renaud
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Energy absorption and damage mechanisms in progressive crushing of corrugated NCF laminates: Fractographic analysis2014In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 110, no 1, p. 110-117Article in journal (Refereed)
    Abstract [en]

    To develop reliable and physically based models for the crash behaviour of composite laminates, a thorough understanding of the failure mechanisms is crucial. Compression tests of corrugated Non-Crimp Fabric (NCF) laminates, made of carbon fibre unidirectional (UD) fabric with a [0/90]3S stacking sequence and epoxy, have been performed to study the energy absorbing damage mechanisms. Samples from the specimens have been studied with optical microscopy and Scanning Electron Microscopy (SEM) to identify the mechanisms involved in the crushing process. The specimens tested fail partly in bending and partly in pure compression with a mode I delamination separating these two regions. In the region failing in pure compression, the main damage mechanisms are kink band formation and matrix cracking of transverse bundles, whereas in the part failing in bending mixed mode delaminations, intralaminar shear fracture of axial bundles and kink band formation through parts of bundles are identified.

  • 88.
    Grauers, Lisa
    et al.
    RISE, Swerea, Swerea SICOMP.
    Szpieg, Magdalena
    RISE, Swerea, Swerea SICOMP.
    Wysocki, M.
    RISE, Swerea, Swerea SICOMP.
    Toll, S.
    KTH Royal Institute of Technology.
    Deformation processes in composites preforms2012In: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite MaterialsConference paper (Refereed)
    Abstract [en]

    The work concerns the inelastic response of composite preforms when subjected to large deformations. The Kawabata equipment has been used to measure the shear and bending properties of the textile reinforcements. In addition, the newly developed triaxial rheometer for out-of-plane shear and compression testing is presented and used. The triaxial rheometer is capable of simultaneous compression and two independent shear deformation modes, allowing for triaxial deformation states. Compared to previous techniques the main benefits are triaxiality, elimination of edge effects and suitability for anisotropic materials. Also, a constitutive theory for the modelling of a wide range of fibrous performs based on hypoplasticity is also presented. The experimental results indicates that even dry preforms behaves viscoelastoplastic as well as showing unsymmetrical behaviour in bending.

  • 89.
    Greenhalgh, Emile S.
    et al.
    Imperial College London, UK.
    Ankersen, Jesper
    GKN Composites Technology Centre, UK.
    Asp, Leif E.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Bismarck, Alexander
    Imperial College London, UK; University of Vienna, Austria.
    Fontana, Quentin
    Fontana Technologies, UK.
    Houlle, Matthieu
    Nanocyl SA, Belgium.
    Kalinka, Gerhard
    BAM Federal Institute Materials Research and Testing, Germany.
    Kucernak, Anthony
    Imperial College London, UK.
    Mistry, Miten
    Imperial College London, UK.
    Nguyen, Sang
    Imperial College London, UK.
    Qian, Hui
    Imperial College London, UK.
    Shaffer, Milo
    Imperial College London, UK.
    Shirshova, Natasha
    Durham Univeristy, UK.
    Steinke, Joachim
    Imperial College London, UK.
    Wienrich, Malte
    BAM Federal Institute Materials Research and Testing, Germany.
    Mechanical, electrical and microstructural characterisation of multifunctional structural power composites2015In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 49, no 15, p. 1823-1834p. 1823-1834Article in journal (Refereed)
    Abstract [en]

    Multifunctional composites which can fulfil more than one role within a system have attracted considerable interest. This work focusses on structural supercapacitors which simultaneously carry mechanical load whilst storing/delivering electrical energy. Critical mechanical properties (in-plane shear and in-plane compression performance) of two monofunctional and four multifunctional materials were characterised, which gave an insight into the relationships between these properties, the microstructures and fracture processes. The reinforcements included baseline T300 fabric, which was then either grafted or sized with carbon nanotubes, whilst the baseline matrix was MTM57, which was blended with ionic liquid and lithium salt (two concentrations) to imbue multifunctionality. The resulting composites exhibited a high degree of matrix heterogeneity, with the ionic liquid phase preferentially forming at the fibres, resulting in poor matrix-dominated properties. However, fibre-dominated properties were not depressed. Thus, it was demonstrated that these materials can now offer weight savings over conventional monofunctional systems when under modest loading.

  • 90.
    Gutkin, Renaud
    et al.
    RISE - Research Institutes of Sweden, Materials and Production, SICOMP.
    Pinho, Silvestre T.
    Imperial College London, UK.
    Combining damage and friction to model compressive damage growth in fibre-reinforced composites2015In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 49, no 20, p. 2483-2495Article in journal (Refereed)
    Abstract [en]

    A material model for unidirectional fibre-reinforced composites coupling damage to the friction acting on newly created microcracks is developed. While existing material models accounting for progressive damage assume that microcracks remain traction free under compressive load, the present model accounts for contact and friction at microcrack closure. The model is validated against experimental data and it is shown that friction can account for part of the non-linear response and the hysteresis loops typically observed in the shear response of composites. Further validation against simple crushing tests is performed and shows that the physics behind crushing is well captured.

  • 91.
    Gutkin, Renaud
    et al.
    RISE, Swerea, Swerea SICOMP.
    Pinho, S.T.
    Imperial College London.
    Predicting fibre kinking and splitting using a finite fracture mechanics formulation2012In: ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite MaterialsConference paper (Refereed)
    Abstract [en]

    This paper presents the development of a model to predict the strength associated with kinkband formation and fibre splitting based on a finite fracture mechanics approach. The model is derived to handle tri-axial stress states, namely longitudinal compression combined with in-plane shear and hydrostatic pressure. Correlations with experimental data from the literature show that the physics of the problem is correctly captured.

  • 92.
    Hagstrand, Per Ola
    et al.
    Chalmers University of Technology, Sweden.
    Oksman, Kristiina
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    Mechanical properties and morphology of flax fiber reinforced melamine-formaldehyde composites2001In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 22, no 4, p. 568-578Article in journal (Refereed)
    Abstract [en]

    The mechanical performance of natural fiber reinforced polymers is often limited owing to a weak fiber-matrix interface. In contrast, melamine-formaldehyde (MF) resins are well known to have a strong adhesion to most cellulose containing materials. In this paper, nonwoven flax fiber mat reinforced and particulate filled MF composites processed by compression molding are studied and compared to a similar MF composite reinforced with glass fibers. Using flax instead of glass fibers has a somewhat negative effect on tensile performance. However, the difference is relatively small, and if density and material cost are taken into account, flax fibers become competitive. Tensile damage is quantified from the stiffness reduction during cyclic straining. Compared to glass fibers, flax fibers generate a material with a considerably lower damage rate. From scanning electron microscopy (SEM), it is found that microcracking takes place mainly in the fiber cell walls and not at the fiber-matrix interface. This sugges ts that the fiber-matrix adhesion is high. The materials are also compared using dynamic mechanical thermal analysis (DMTA) and water absorption measurements.

  • 93.
    Hajlane, Abdelghani
    et al.
    Luleå University of Technology, Sweden; Cadi Ayyad University, Morocco.
    Kaddami, Hamid
    Cadi Ayyad University, Morocco.
    Joffe, Roberts
    RISE - Research Institutes of Sweden, Swerea, Swerea SICOMP. Luleå University of Technology, Sweden.
    Chemical modification of regenerated cellulose fibres by cellulose nano-crystals: Towards hierarchical structure for structural composites reinforcement2017In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 100, p. 41-50Article in journal (Refereed)
    Abstract [en]

    A simple and innovative new route, with less negative impact on the environment, for depositing and hope-grafting cellulose nano-crystals onto the surface of regenerated cellulose fibres (Cordenka 700 Super 3), using γ-methacryloxypropyltrimethoxysilane as coupling agent, is presented. Hierarchical cellulosic structure involving micro-scale fibres and nano-scale cellulose crystal network was created as verified by the scanning electron microscopy. The fibres were initially oxidised by optimized concentration of cerium ammonium nitrate to generate radicals on the cellulose backbone in order to polymerize the coupling agent at the surface. Infrared spectroscopy and scanning electron microscopy confirmed the chemical polymerisation of MPS onto regenerated cellulose fibres without enabling to show the chemical bonding between silane and nano-crystals. However, tensile test which was performed to study the impact of different treatments on mechanical properties of regenerated cellulose fibres, revealed that the modification by silane decreased the stiffness and strength of fibres (22% and 10% decrease, respectively) while the strain at failure was increased. These changes were attributed to the treatment conditions which may have induced the disorder and the misalignment of the structure of cellulose fibres (e.g. axial orientation of molecular chains and crystalline phase of the fibre has been reduced). This assumption is supported by the results from successive loading-unloading test of the fibre bundle. However, after depositing cellulose nano-crystals onto the fibre’s surface, the stiffness was recovered (20% increase in comparison to MPS treated fibres) while the strength and strain at failure remained at the same order of magnitude as for fibres treated only by the coupling agent.

  • 94.
    Heshmati, Mohsen
    et al.
    Chalmers University of Technology, Sweden.
    Haghani, Reza
    Chalmers University of Technology, Sweden.
    Al-Emrani, Muhammed
    Chalmers University of Technology, Sweden.
    André, Alann
    RISE - Research Institutes of Sweden (2017-2019), Materials and Production, SICOMP.
    On the strength prediction of adhesively bonded FRP-steel joints using cohesive zone modelling2018In: Theoretical and applied fracture mechanics (Print), ISSN 0167-8442, E-ISSN 1872-7638, Vol. 93, p. 64-78Article in journal (Refereed)
    Abstract [en]

    The variety of failure modes that are likely to occur in fibre-reinforced polymer (FRP)/steel joints used in the construction industry adds to the complexity associated with the design of these joints. This variation in possible failure modes is mainly attributed to the lack of a controlled application environment and to rather insufficient quality assurance protocols and procedures. The use of energy-based methods such as, cohesive zone modelling (CZM), can be a solution to circumvent such complexities. This paper investigates a number of issues related to CZM analyses of FRP/steel adhesive joints using various test configurations and a comprehensive numerical study. Parameters such as the effect of shape and type of cohesive law, crack path location, length of damage process zone, variations of adhesive and FRP properties, and different failure modes including cohesive, interfacial debonding and FRP failure on the strength of joints are investigated. The results show that the behaviour of the tested joints is accurately predicted provided that the variation of failure modes are taken into account. Moreover, it is shown that the damage process zone in adhesive layer is directly proportional to the shape of cohesive laws. This feature can be employed in the design phase to ensure sufficient overlap length and to account for important in-service parameters such as temperature and moisture.

  • 95.
    Holmberg, Aaron
    RISE, Swerea, Swerea SICOMP.
    Characterization of Carbon Fiber and Glass Fiber Fabrics by drape fixture2009Report (Refereed)
  • 96.
    Holmberg, Anders
    RISE, Swerea, Swerea SICOMP.
    Overview of binder systems for aeronautical applications2007Report (Refereed)
  • 97.
    Holmberg, Anders
    RISE, Swerea, Swerea SICOMP.
    Validation of NCF global permeability (and compaction) models2005Report (Refereed)
  • 98.
    Holmberg, Anders
    et al.
    RISE, Swerea, Swerea SICOMP.
    Engberg, David
    RISE, Swerea, Swerea SICOMP.
    Egenskaper hos textila armeringar vid drapering och formning: en översikt2008Report (Refereed)
  • 99.
    Holmberg, Anders
    et al.
    RISE, Swerea, Swerea SICOMP.
    Lindmark, Sive
    RISE, Swerea, Swerea SICOMP.
    Serrander, Tore
    RISE, Swerea, Swerea SICOMP.
    Mekanisk Provning av Vakuuminjicerade Rovicore Laminat1999Report (Refereed)
  • 100.
    Holmberg, Anders
    et al.
    RISE, Swerea, Swerea SICOMP.
    Mattsson, David
    RISE, Swerea, Swerea SICOMP.
    Lundmark, Peter
    RISE, Swerea, Swerea SICOMP.
    Svanberg, Magnus
    RISE, Swerea, Swerea SICOMP.
    On diffusion in heterogeneous materials and diffusion simulations in ANSYS2008Report (Refereed)
123456 51 - 100 of 291
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