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Rouhi, M., Juntikka, M., Landberg, J. & Wysocki, M. (2019). Assessing models for the prediction of mechanical properties for the recycled short fibre composites. Journal of reinforced plastics and composites (Print), 38(10), 454-466
Open this publication in new window or tab >>Assessing models for the prediction of mechanical properties for the recycled short fibre composites
2019 (English)In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 38, no 10, p. 454-466Article in journal (Refereed) Published
Abstract [en]

Processing of polymer fibre composites has a remarkable influence on their mechanical performance. These mechanical properties are even more influenced when using recycled reinforcement. Therefore, we place particular attention on the evaluation of micromechanical models to estimate the mechanical properties and compare them against the experimental results of the manufactured composites from recycled carbon fibre material. For the manufacturing process, an epoxy matrix and carbon fibre production cut-offs as reinforcing material are incorporated using a vacuum infusion process. In addition, continuous textile reinforcement in combination with the epoxy matrix is used as reference material to evaluate the degradation of mechanical performance of the recycled composite. The experimental results show higher degradation of the composite strength compared to the stiffness properties. Observations from the modelling also show the same trend as the deviation between the theoretical and experimental results is lower for stiffness comparisons than the strength calculations. Yet still, good mechanical performance for specific applications can be expected from these materials.

Keywords
carbon fibres, Composite recycling, mechanical properties, micromechanics, Carbon fibers, Recycling, Reinforcement, Stiffness, Manufacturing process, Mechanical performance, Micromechanical model, Prediction of mechanical properties, Recycled carbon fibres, Reinforcing materials, Short fibre composites, Vacuum infusion process
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-37753 (URN)10.1177/0731684418824404 (DOI)2-s2.0-85060734278 (Scopus ID)
Available from: 2019-02-11 Created: 2019-02-11 Last updated: 2019-06-28Bibliographically approved
Farajzadeh Khosroshahi, S., Olsson, R., Wysocki, M., Zaccariotto, M. & Galvanetto, U. (2018). Response of a helmet liner under biaxial loading. Polymer testing, 72, 110-114
Open this publication in new window or tab >>Response of a helmet liner under biaxial loading
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2018 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 72, p. 110-114Article in journal (Refereed) Published
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.

Keywords
Biaxial mechanical response, EPS, Helmet, Oblique impact, Compression testing, Safety devices, Shear stress, Compressive tests, Experimental test, Mechanical response, Reliable results, Rotational acceleration, Uni-axial compression tests, Accident prevention
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-35573 (URN)10.1016/j.polymertesting.2018.10.012 (DOI)2-s2.0-85054874584 (Scopus ID)
Note

 Funding details: FP7-PEOPLE-2013-ITN-608092, REA, Research Executive Agency; Funding text: The research leading to these results has received funding from the People Programme (Marie Sklodowska Curie Actions) of the European Union’s Seventh Framework FP7/2007-2013/under REA grant agreement n° [ FP7-PEOPLE-2013-ITN-608092 ] and from the ECCELLENZA programme of the CARIPARO foundation under the REDIPhE project.

Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2019-06-28Bibliographically approved
Rouhi, M. & Wysocki, M. (2018). SIMULATION OF 3D PREPREG CONSOLIDATIONPROCESS USING SOLID SHELL ELEMENTS. In: : . Paper presented at 14th International Conference on Flow Processes in Composite Materials, 30 May - 1 June, 2018.
Open this publication in new window or tab >>SIMULATION OF 3D PREPREG CONSOLIDATIONPROCESS USING SOLID SHELL ELEMENTS
2018 (English)Conference paper, Published paper (Other academic)
Abstract [en]

In process simulation of composite materials, 3D simulation of manufacturing processes is desirableconsidering the manufacturing trend where parts became more complex leading to complex3D stress-strain states. Moreover, coupling of sub-processes that are happening simultaneouslysuch as macro-scale preform processes, micro-infiltration and solid and fluid interactionrequires full 3D description of the problem.The development is exemplified considering compression moulding process of prepregs wherethe main focus of the modeling will be on the compression and compaction of directionalprepreg laminate and flow consolidation. To this end, the theory of two phase porous mediais used along with assuming hyper-elastic material response for the laminate to formulatethe problem. A finite element formulation and implementation of the two-phase problem is developedfor incompressible constituents and is implemented in a user defined element (UEL)to be used with Abaqus.

Keywords
Compression moulding, Solid shell element, Dual scale flow, Consolidation, Abaqus UEL.
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36100 (URN)
Conference
14th International Conference on Flow Processes in Composite Materials, 30 May - 1 June, 2018
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-06-20Bibliographically approved
Saseendran, S., Wysocki, M. & Varna, J. (2017). Effect of degree of cure and time on viscoelastic poisson's ratio. In: ICCM International Conferences on Composite Materials: . Paper presented at 21st International Conference on Composite Materials, ICCM 2017, 20 August 2017 through 25 August 2017. International Committee on Composite Materials
Open this publication in new window or tab >>Effect of degree of cure and time on viscoelastic poisson's ratio
2017 (English)In: ICCM International Conferences on Composite Materials, International Committee on Composite Materials , 2017Conference paper, Published paper (Refereed)
Abstract [en]

The Poisson's ratio of a solid under deformation is classically defined as the negative of the ratio between the lateral or transverse strain and the axial strain. Ideally for an elastic material, the Poisson's ratio is assumed to be a constant. However, for viscoelastic materials like polymers and polymer matrix composites this is also likely influenced by various factors like time [1], temperature, degree of cure and also on the strain. In this work, the evolution of the viscoelastic Poisson's ratio of the commercial LY5052 epoxy resin is studied under uniaxial tension subject to constant deformation stress relaxation testing. Measurements of the Poisson ratios are performed using contact extensometers and strain gages. Samples at five different cure states are manufactured and investigated. The relaxation testing is performed by loading the samples to 0.5% longitudinal strain and monitoring the relaxation behavior over a period of 24 hours per cure state. Poisson's ratio is observed to evolve from 0.32 to 0.44 over time depending on the cure state. Moreover the data indicates that the individual Poisson's ratio curves can be shifted horizontally following time-cure superposition. The shift functions used for this horizontal shifting are similar to those identified for DMTA tests for storage modulus under identical conditions. Following horizontal shifting, master curves that show the evolution of Poisson's ratio over time can be created for a particular reference cure state. This similarity of the shift functions in both micro-scale DMTA testing and macro-scale relaxation testing is an indicator of the validity of the shift factors. The observation is used to further develop a viscoelastic model which identifies the total shift function as the product of the temperature and cure shift functions. 

Place, publisher, year, edition, pages
International Committee on Composite Materials, 2017
Keywords
Cure dependence, Poisson's ratio, Stress relaxation, Time dependence, Viscoelasticity
National Category
Materials Engineering
Identifiers
urn:nbn:se:ri:diva-38096 (URN)2-s2.0-85053127999 (Scopus ID)
Conference
21st International Conference on Composite Materials, ICCM 2017, 20 August 2017 through 25 August 2017
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-13Bibliographically approved
Saseendran, S., Wysocki, M. & Varna, J. (2017). Evolution of viscoelastic behaviour of a curing LY5052 epoxy resin in the rubbery state. Advanced Composite Materials, 26(6), 553-567
Open this publication in new window or tab >>Evolution of viscoelastic behaviour of a curing LY5052 epoxy resin in the rubbery state
2017 (English)In: Advanced Composite Materials, ISSN 0924-3046, E-ISSN 1568-5519, Vol. 26, no 6, p. 553-567Article in journal (Refereed) Published
Abstract [en]

In this work, we investigate the relationship between the rubbery modulus and the degree of cure for partially to fully cured LY5052 epoxy resin. In particular, this paper experimentally tests an existing model formulated for shear modulus by redefining for in the tensile storage modulus. Experiments to characterize viscoelastic behaviour were performed in a dynamic mechanical and thermal analysis (DMTA) instrument in the frequency domain. Master curves are then created from DMTA using general time–temperature–cure superposition. The master curves are then normalized using the model so that the master curve does not depend on the properties in the rubbery region. This results in a unique master curve that describes the viscoelastic behaviour of the LY5052 epoxy resin for the given conditions. Once the relationship between the rubbery modulus and the degree of cure has been established, the amount of experimental characterization can be reduced. This could lead to the development of simplified experimental methodologies and simplified models to characterize the viscoelasticity of low molecular weight resins like the LY5052 epoxy resin system.

Keywords
curing, mechanical properties, thermal analysis, thermosetting resin, Dynamic mechanical analysis, Elastic moduli, Frequency domain analysis, Thermoanalysis, Thermosets, Viscoelasticity, Degree of cure, Dynamic mechanical, Epoxy resin system, Experimental characterization, Experimental methodology, Frequency domains, Low molecular weight resin, Viscoelastic behaviour, Epoxy resins
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-29321 (URN)10.1080/09243046.2017.1310076 (DOI)2-s2.0-85017361024 (Scopus ID)
Available from: 2017-05-12 Created: 2017-05-12 Last updated: 2019-01-28Bibliographically approved
Wysocki, M., Rouhi, M., Vyas, G. & Toll, S. (2016). Constitutive models for transversely isotropic fibreprefrom in composite manufacturing. In: 13th International Conference on Flow Processes in Composite Materials (FPCM 13): . Paper presented at 13th International Conference on Flow Processing in Composite Materials (FPCM13), July 6-9, 2016, Kyoto, Japan. , Article ID 20.
Open this publication in new window or tab >>Constitutive models for transversely isotropic fibreprefrom in composite manufacturing
2016 (English)In: 13th International Conference on Flow Processes in Composite Materials (FPCM 13), 2016, article id 20Conference paper, Published paper (Other academic)
Abstract [en]

The present contribution is an attempt to model a prepreg that is assumed to have approximatelystraight and parallel fibers which in an unloaded state has a transversely isotropicsymmetry about the fiber axis n. It is further assumed that the prepreg behaves elastic undera purely volumetric deformation, as well as under axial stretching in the fiber direction.A two-scale flow highly coupled to the fiber bed deformation is also being modelled usingporomechanics. The framework comprises a nonlinear compressible fiber network saturatedwith incompressible fluid phase.

Keywords
Transversely isotropic preform, Dual scale flow, Process modeling
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36104 (URN)
Conference
13th International Conference on Flow Processing in Composite Materials (FPCM13), July 6-9, 2016, Kyoto, Japan
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-06-20Bibliographically approved
Rouhi, M., Costa, S., Wysocki, M. & Gutkin, R. (2016). Coupling process and structural simulations in crash application. In: 31st ASC Technical Conference and ASTM D30 Meeting: . Paper presented at 31st ASC Technical Conference and ASTM D30 Meeting, September 19-22, 2016, Williamsburg, Virginia.
Open this publication in new window or tab >>Coupling process and structural simulations in crash application
2016 (English)In: 31st ASC Technical Conference and ASTM D30 Meeting, 2016Conference paper, Published paper (Other academic)
Abstract [en]

The energy absorbed during crushing of composite structures is strongly dependent on the layup, fiber architecture and type of resin used. Modeling of the crash behavior of composites is therefore highly influenced by the composite material system chosen, and current constitutive models must be improved to include/account for the inherent properties from the manufacturing step. The ultimate goal of this contribution is to optimize the material system and manufacturing method for the required crushing performance in terms of energy absorption and cost. A first outcome of the study will be to provide information regarding the properties of the final manufactured composite material such as residual stresses and effects of defects. These properties are then used in the development of crash models. A robust link between manufacturing, experiments and crushing simulations is vital where there should be a generic routine towards the data transfer and constitutive models. The study of effects of defects will affect the input data into the material and constitutive models in form of change in strength and stiffness properties of the material. In this contribution, an experimental study on the material response under quasistatic crushing is performed where the manufacturing effects on the material properties are considered based on estimated data provided from vacuum infusion simulation. The crushing simulations are performed with ABAQUS where the material model developed in-house, which is a physically based damage model based on the LaRC05 failure criterion and progressive damage, is chosen to model the constitutive behavior. The parameters that are transferred to the system from manufacturing simulation are fiber content and voids. Consideration of these parameters into the constitutive behavior of the structure will directly influence the structural response. A parametric study is completed and results are discussed.

National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36103 (URN)
Conference
31st ASC Technical Conference and ASTM D30 Meeting, September 19-22, 2016, Williamsburg, Virginia
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-06-20Bibliographically approved
Rouhi, M. S., Wysocki, M. & Larsson, R. (2016). Holistic modeling of composites manufacturing using poromechanics. Advanced Manufacturing: Polymer & Composites Science, 2(1), 14-26
Open this publication in new window or tab >>Holistic modeling of composites manufacturing using poromechanics
2016 (English)In: Advanced Manufacturing: Polymer & Composites Science, ISSN 2055-0340, Vol. 2, no 1, p. 14-26Article in journal (Refereed) Published
Abstract [en]

AbstractIn the present paper, we present a novel finite-element method capable of handling most of the physics arising in the resin wet-out step for any composite system and processing case. The method is based on a compressible two-phase continuum formulation where a key feature is to model the involved physics via innovative use of the compressibility of the phases. On the one hand, the fluid-phase compressibility is used to capture the physics of the advancing resin front as well as the physics behind the flow front. On the other hand, solid-phase compressibility is used to model micro-infiltration of the resin and the corresponding preform compaction, essentially considered as a fluid sink problem. Finally, the generic porous media model is formulated in the finite strain regime. The model is implemented and demonstrated for different manufacturing methods and the results with respect to each example are presented. The degree of saturation, pressure distribution, preform deformation, and reaction forces are some of the post-processed results for different manufacturing methods. The ultimate goal of this contribution is to establish a unified generic and general simulation tool for structural (long fiber) composite processing where, to this date, there is no single FE-based tool available commercially for this purpose.

Keywords
Composite materials, Manufacturing modeling, Poromechanics, Compressible phases, Flow front tracking, FE method
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36101 (URN)10.1080/20550340.2016.1141457 (DOI)
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-07-01Bibliographically approved
Rouhi, M., Wysocki, M. & Larsson, R. (2016). SIMULATION OF 3D RTM PROCESS USING SOLID SHELL ELEMENT. In: 13th International Conference on Flow Processes in Composite Materials (FPCM 13): . Paper presented at 13th International Conference on Flow Processing in Composite Materials (FPCM13), July 6-9, 2016, Kyoto, Japan.
Open this publication in new window or tab >>SIMULATION OF 3D RTM PROCESS USING SOLID SHELL ELEMENT
2016 (English)In: 13th International Conference on Flow Processes in Composite Materials (FPCM 13), 2016Conference paper, Published paper (Other academic)
Abstract [en]

In the era of process modeling of composite materials, 3D simulation of manufacturing processesis desirable considering the manufacturing trend where parts became more complexleading to complex 3D stress-strain states. Moreover, coupling of sub-processes that are happeningsimultaneously such as macro-scale preform processes, flow advancement and solidand fluid interaction requires full 3D description of the problem.The development is exemplified considering RTM process where the main focus of the modelingwill be on the flow advancement into fiber preform and flow front capturing. To thisend, the theory of two phase porous media is used along with assuming hyper-elastic materialresponse for the fiber bed to formulate the problem. A finite element formulation and implementationof the two-phase problem is developed for incompressible constituents

Keywords
Solid shell element, Flow front capturing, 3D flow process
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36105 (URN)
Conference
13th International Conference on Flow Processing in Composite Materials (FPCM13), July 6-9, 2016, Kyoto, Japan
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-06-26Bibliographically approved
Rouhi, M. S., Wysocki, M. & Larsson, R. (2015). Experimental assessment of dual-scale resin flow-deformation in composites processing. Composites. Part A, Applied science and manufacturing, 76, 215-223
Open this publication in new window or tab >>Experimental assessment of dual-scale resin flow-deformation in composites processing
2015 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 76, p. 215-223Article in journal (Refereed) Published
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.

Keywords
B. Anisotropy, B. Stress relaxation, C. Finite element analysis (FEA), Poromechanics
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-36102 (URN)10.1016/j.compositesa.2015.05.034 (DOI)
Available from: 2018-11-09 Created: 2018-11-09 Last updated: 2019-07-04Bibliographically approved
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2841-7188

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