| 1. |
- Carlson, Tony, et al.
(författare)
-
CFRP structural capacitor materials for automotive applications
- 2011
-
Ingår i: Plastics, rubber and composites. - 1465-8011 .- 1743-2898. ; 40:6/7, s. 311-316
-
Konferensbidrag (refereegranskat)abstract
- In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy prepreg woven lamina separated by a polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and tearing force. The developed structural carbon fibre reinforced polymer (CFRP) capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential. © Institute of Materials, Minerals and Mining 2011.
|
|
| 2. |
- Carlson, Tony, et al.
(författare)
-
Structural capacitor materials made from carbon fibre epoxy composites
- 2010
-
Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 70:7, s. 1135-1140
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, an approach towards realising novel multifunctional polymer composites is presented. A series of structural capacitor materials made from carbon fibre reinforced polymers have been developed, manufactured and tested. The structural capacitor materials were made from carbon fibre epoxy pre-preg woven laminae separated by a paper or polymer film dielectric separator. The structural capacitor multifunctional performance was characterised measuring capacitance, dielectric strength and interlaminar shear strength. The developed structural CFRP capacitor designs employing polymer film dielectrics (PA, PC and PET) offer remarkable multifunctional potential. © 2010 Elsevier Ltd.
|
|
| 3. |
- Ekstedt, Sofia, et al.
(författare)
-
Structural batteries made from fibre reinforced composites
- 2009
-
Ingår i: ICCM 17, Edinburgh. - London : IOM Communications.
-
Konferensbidrag (refereegranskat)abstract
- Structural, fibre reinforced, battery prototypes with two types of electrolyte matrix material, a gel and a solid polymer, have been manufactured. This was to confirm the concept of using carbon fibres as current collector in the anode as well as providing a mechanical load-carrying functionality. As a result, functioning batteries with gel electrolyte have been produced and their properties have been characterised.
|
|
| 4. |
- Ekstedt, Sofia, et al.
(författare)
-
Structural batteries made from fibre reinforced composites
- 2010
-
Ingår i: Plastics, rubber and composites. - 1465-8011 .- 1743-2898. ; 39:3-5, s. 148-150
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 5. |
- Farajzadeh Khosroshahi, S., et al.
(författare)
-
Response of a helmet liner under biaxial loading
- 2018
-
Ingår i: Polymer testing. - : Elsevier BV. - 0142-9418 .- 1873-2348. ; 72, s. 110-114
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 6. |
- Francis, Sachin, 1991, et al.
(författare)
-
Characterisation of tape-based carbon fibre thermoplastic discontinuous composites for energy absorption
- 2021
-
Ingår i: Plastics, rubber and composites. - : Taylor and Francis Ltd.. - 1465-8011 .- 1743-2898. ; 50:7, s. 351-
-
Tidskriftsartikel (refereegranskat)abstract
- Tape-based discontinuous composite is a relatively new type of composite material that offers improved mechanical properties for similar process-ability compared to Sheet Moulding Compound or Bulk Moulding Compound. This makes it potentially attractive for the automotive industry. In this paper, a thin-ply carbon fibre reinforced polypropylene-based discontinuous composite is studied. Mechanical tests are performed to obtain the tensile, compression and shear behaviour of the material. The energy absorption via tearing is also studied to assess the suitability of the material for energy absorption applications, such as crash-boxes. The tearing test results show a large degree of plastic deformation and an advancing damage front leading to higher specific energy absorption via tearing compared to conventional composite materials. © 2021 The Author(s).
|
|
| 7. |
- Larijani, Nasim, et al.
(författare)
-
Metal onto polymer composite casting: Degradation behaviour and mechanical performance
- 2009
-
Konferensbidrag (refereegranskat)abstract
- A general three dimensional finite element model for modelling thermal degradation of polymer composites due to thermal loading is presented. In particular, the model is intended for modelling the thermal degradation of polymer composites due to "metal onto composites casting" with lightweight alloys. The model is implemented as a user defined subroutine into the general purpose FEpackage ABAQUS©. The applicability of the code was demonstrated by analysing the casting process of an aluminium alloy onto composite rods, resulting in a shrinkage fit. To succeed in manufacturing of this type of joint, a delicate balance between thermal loadings, metal shrinkage, composite degradation and the overall cooling must be met. The proposed subroutine together with finite element models provides the spatial distribution of these field variables, allowing for subsequent optimization of the assembly. In order to asses the quality of the composite/metal joints pull-out tests of cylindrical composite rods were performed and compared to numerical simulation predictions.
|
|
| 8. |
- Larsson, Ragnar, 1960, et al.
(författare)
-
Free surface flow and preform deformation in composites manufacturing based on porous media theory
- 2012
-
Ingår i: European journal of mechanics. A, Solids. - : Elsevier BV. - 0997-7538 .- 1873-7285. ; 31:1, s. 12-jan
-
Tidskriftsartikel (refereegranskat)abstract
- In the present contribution an infusion simulation tool is developed, applicable to a quite wide range of composites manufacturing technologies. The paper focusses on isothermal, infusion like manufacturing processes involving highly deformable preforms and a free surface resin flow. There are two major issues addressed at the modelling of the infusion processes: The first one is the highly deformable preform and its shape due to the interaction between external pressure loading and the intrinsic fluid pressure. The second issue concerns the migrating free surface due to resin infiltration into the fibrous preform. To resolve these both issues simultaneously, a compressible two-phase porous media formulation is put forward involving an additional liquid mass balance relationship as compared to the standard compressible porous media formulation. As a result a governing equation for saturation degree evolution is established, which is used to monitor the free surface problem directly in terms of the compressible continuum formulation traversing into incompressibility with increasing partial saturation degree. A staggered finite element based solution procedure is advocated for the total solution advancement, involving, on the one hand, the saturation dependent porous media formulation, and, on the other hand, the computation of the saturation degree. The proposed formulation has been implemented and numerical results are provided, showing the convergence of the staggered approach, and the assessment of the proposed approach against a 1D analytical model. In addition, the infusion of a "hat" beam is considered. © 2011 Elsevier Masson SAS. All rights reserved.
|
|
| 9. |
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Pupure, Liva
(författare)
-
Non-linear model applied on composites exhibiting inelastic behavior: development and validation
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The polymeric composite materials are in high demand by industries where light and strong materials are required. Although manmade fiber (e.g. glass, carbon, aramid fibers) are most often used to reinforce polymers, natural fibers due to their environmental friendliness and sustainability have been also considered. Natural fiber composites have shown to have great potential as a substitute for conventional glass fiber materials. However, bio-based composites exhibit highly non-linear behavior, besides they are very sensitive to elevated moisture and temperature. Therefore, careful design and optimization of composite properties defined by constituents, composition and internal structure is needed to meet requirements of real-life applications. This can be done by using accurate models that can take into account factors responsible for inelastic behavior of these materials. The initial part of this thesis is dealing with development of phenomenological approach to predict inelastic behavior of composites in tension. Viscoelasticity and viscoplasticity was analyzed in short term creep tests and modulus degradation in stiffness degradation tests. Schapery’s model for viscoelasticity and Zapa’s model for viscoplasticity was used to characterize nonlinearity. This method was then validated on short, randomly oriented fiber composites with different cellulosic fibers (flax, viscose) and bio-polymers (PLA, Lignin). The elastic modulus, tensile stress-strain curves and failure were analyzed at different humidity and temperature levels. Results showed high sensitivity to moisture and temperature and highly non-linear behavior of these materials. Modeling showed good agreement between experimental data and simulations.Since there is need for simulations of strain controlled tests, this model was rewritten in inverted incremental form. Simulations of stress-strain curves showed, that predictions are more accurate, when characterization of viscoelastic and viscoplastic parameters was done at stresses close to failure. However, due to creep rapture it was not always possible to characterize material at high stresses and in this case viscoelastic functions have to be extrapolated. The stress-strain curves can be then used to further adjust extrapolation of model parameters.The model developed in the first part of the thesis proved to be capable of predicting behavior of short fiber composites with good accuracy. However, in order to carry out simulations input parameters have to be experimentally obtained and it has to be done for every composite that is studied. The second part of this thesis is dedicated to development of constitutive model which uses parameters of constituents to predict behavior of material with any composition. This model then is applied on semi-structural natural fiber composites consisting of bio-based resins reinforced with continuous cellulosic fibers. Mechanical properties of different bio-based thermoset resins and regenerated cellulose fibers have been analyzed. Results showed comparable properties of bio-based and synthetic epoxy resins, even at elevated humidity levels, but high scattering of properties from sample to sample. They also showed that bio-based resin exhibit limited non-linearity whereas regenerated cellulose fiber is highly non-linear.In order to avoid large scatter typical for bio-based materials and improve accuracy of the model, methodology for parameter identification for viscoplastic model with use of only one sample has been suggested.The objective here is to simulate strain controlled tests and the most convenient way to do it is with Schapery’s strain formulation model. The parameters for such model can be obtained from relaxation tests, where viscoelastic strain is kept constant but due to presence of viscoplastic strain component such experiments are difficult to perform. Instead, constituents exhibiting viscoplastic behavior have been characterized in creep and viscoelastic parameters for Schapery’s strain formulation are obtained from simulations of relaxation tests with inverted incremental model. Then these parameters are used to simulate behavior of composite subjected to iso-strain conditions.
|
|
| 15. |
- Rouhi, Mohammad, et al.
(författare)
-
Assessing models for the prediction of mechanical properties for the recycled short fibre composites
- 2019
-
Ingår i: Journal of reinforced plastics and composites (Print). - : SAGE Publications. - 0731-6844 .- 1530-7964. ; 38:10, s. 454-466
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 16. |
- Rouhi, Mohammad, et al.
(författare)
-
Coupling process and structural simulations in crash application
- 2016
-
Ingår i: 31st ASC Technical Conference and ASTM D30 Meeting.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
Composite manufacturing modeling using porous media theory
- 2012
-
Ingår i: 25th Nordic Seminar on Computational Mechanics (NSCM25), Lund, Swede, 25-26 October 2012. ; , s. 295-298
-
Konferensbidrag (refereegranskat)abstract
- We recently developed a simulation tool to simulate a quite wide class of composites manufacturing processes based on a compressible porous media theory formulation involving three constituents, solid, fluid and pore gas embedded in the voids. The aim of this tool is: firstly to model the highly deformable preform and its interaction with external loading and the intrinsic fluid pressure as well as the resulting changes in permeability, compaction and level of saturation. Secondly, the aim is to track the resin flow front during the infusion process using the continuum formulation itself, thereby avoiding methods like level set.
|
|
| 20. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
CONSTITUTIVE MODELLING OF ANISOTROPIC TWO-SCALE FLOW
- 2012
-
Ingår i: 15th European Conference on Composite Material (ECCM15) - Venice- Italy 2012. - : European Conference on Composite Materials, ECCM.
-
Konferensbidrag (refereegranskat)abstract
- We recently developed a simulation tool to simulate a quite wide class of infusion processes based on a compressible porous media theory formulation involving three constituents, solid, fluid and pore gas embedded in the voids. The aim of this tool is: firstly to model the highly deformable preform and its interaction with external loading and the intrinsic fluid pressure as well as the resulting changes in permeability, compaction and level of saturation. Secondly, the aim is to track the resin flow front during the infusion process using the continuum formulation itself, thereby avoiding methods like level set, etc. [1]. In this contribution, we present a permeability model applied within the modeling framework to account for anisotropic flow in the fibre bed. The ultimate goal of the approach is to be able to simulate the infusion of high performance, large scale composite structures, in an optimized and controlled fashion.
|
|
| 21. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
Experimental assessment of coupled dual-scale flow-deformation processes in composites manufacturing
- 2015
-
Ingår i: Composites Part A: Applied Science and Manufacturing. - : Elsevier BV. - 1359-835X. ; 76, s. 215-223
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 22. |
- Rouhi, Mohammad S., et al.
(författare)
-
Experimental assessment of dual-scale resin flow-deformation in composites processing
- 2015
-
Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 76, s. 215-223
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 23. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
FE modeling and numerical implemtation of flow-deformation processes in composites manufacturing
- 2013
-
Ingår i: ICCM International Conferences on Composite Materials. - : International Committee on Composite Materials. ; 2013-July, s. 5292-5299, s. 5292-5299
-
Konferensbidrag (refereegranskat)abstract
- In present work, we attempt to unify the modeling of different sub-processes under the umbrella of two-phase porous media theory. Two sub processes are considered: (1) the wetting and compaction of individual plies and (2) the overall preform deformation and macroscopic Darcian flow. The idea is to identify a set of relevant constituents, i.e. particles, voids and liquids, and assign them to pertinent media. The result is a set of overlapping continuous media, each having its own density-, velocity- and stress field on the macroscopic scale. In addition, we introduce internal variables to describe irreversible micro-processes in the system, such as microscopic infiltration and preform deformation. In this work we extend the previous developments, coupling the preform deformation on different scales to the process of micro infiltration, with respect to the modeling of the micro-compaction as well as the Darcian interaction on the macro scale. A coupled displacement-pressure, geometrically non-linear, finite element model is presented. The approach is applied to a representative numerical example where we used parameter values out of the literature and estimates from our own micrographs.
|
|
| 24. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
Holistic modeling of composites manufacturing using poromechanics
- 2016
-
Ingår i: Advanced Manufacturing: Polymer and Composites Science. - : Informa UK Limited. - 2055-0359 .- 2055-0340. ; 2
-
Tidskriftsartikel (refereegranskat)abstract
- In the present paper we present a novel finite element method capable of handling most of thephysics arising in the resin wet-out step for any composite system and processing case. The methodis based on a compressible two-phase continuum formulation where a key feature is to model theinvolved physics via innovative use of the compressibility of the phases. On the one hand, thefluid phase compressibility is used to capture the physics of the advancing resin front as well asthe physics behind the flow front. On the other hand, solid phase compressibility is used to modelmicro infiltration of the resin and the corresponding preform compaction, essentially consideredas a fluid sink problem. Finally, the generic porous media model is formulated in the finite strainregime. The model has been implemented and demonstrated for different manufacturing methodsand the results with respect to each example is presented. The degree of saturation, pressuredistribution, preform deformation and reaction forces are some of the post-processed results fordifferent manufacturing methods. The ultimate goal of this contribution is to establish an unifiedgeneric and general simulation tool for structural (long fiber) composite processing where, to thisdate, there is no single FE based tool available commercially for this purpose.
|
|
| 25. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
Modeling of coupled dual-scale flow–deformation processes in composites manufacturing
- 2013
-
Ingår i: Composites Part A: Applied Science and Manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 46:1, s. 108-116
-
Tidskriftsartikel (refereegranskat)abstract
- The present contribution is a part of the work towards a framework for holistic modeling of compositesmanufacturing. 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 VacuumBag Only (VBO) prepregs. The formulation considers coupling effects between macro-scale preform processesand meso-scale ply processes as well as coupling effects between the solid and fluid phases. Theframework comprises a nonlinear compressible fiber network saturated with incompressible fluid phase.Internal variables are introduced in terms of solid compressibility to describe the irreversible mesoscopicinfiltration and reversible preform compaction processes. As a main result a coupled displacement–pressure, geometrically nonlinear, finite element simulation tool is developed. The paper is concludedwith a numerical example, where a relaxation–compression test of a planar fluid filled VBO preform atglobally un-drained and partly drained conditions is considered.
|
|
| 26. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
Modeling resin flow and preform deformation in composite manufacturing based on partially saturated porous media theory
- 2010
-
Ingår i: Procedeing of 23rd Nordic Seminar on Computational Mechanics. ; , s. 142-145
-
Konferensbidrag (refereegranskat)abstract
- In this contribution a generic algorithm to simulate resin infusion in composites manufacturing technologies such as Liquid Resin Infusion (LRI) and Resin Transfer Molding(RTM) is developed. The most important challenge to be addressed is the migration of free surface due to resin infiltration into the highly deformable fibrous preform. To do so, a compressible two-phase porous media formulation is put forward for the problem formulation and a staggered finite element based solution procedure is advocated for the total solution advancement. The approach automatically monitors the free surface, whereby the monitoring of the resin front migration using e.g. level set or front tracking control is completely avoided. The method is exemplified using a hat stringer geometry considering both manufacturing methods.
|
|
| 27. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
Modeling resin flow, preform deformations and residual stresses in RTM manufacturing
- 2011
-
Ingår i: Proc. of International Conference on Manufacturing of Advanced Composites, ICMAC 2011, Belfast, Northern Ireland.
-
Konferensbidrag (refereegranskat)abstract
- In the present contribution a generic algorithm is developed to simulate resin infusion in a wide range of popular composites manufacturing technologies, such as Liquid Resin Infusion (LRI) and Resin Transfer Molding (RTM). The ultimate goal is to model a complete manufacturing chain, allowing us to predict the final product properties of the composite material. The major challenges to be addressed by in this modelling vary between different processing steps. One of the most important one concerns the migration of the free surface due to resin infiltration into the highly deformable fibrous preform. Considering the LRI process, the modeling challenge is to predict the final shape of a highly deformable preform due to interaction between external loading and the intrinsic fluid pressure. Moreover, in the RTM process the constant compaction load due to rigid top part of the mold needs to be modeled. To resolve both these processes in one single framework, a compressible two-phase porous media formulation is put forward. The developed model involves a fluid compressibility and permeability dependence on the saturation degree. This is to account for the coupled response of partially saturated solid-fluid media, typical for the transition zone at the free surfacebetween full- and non-saturation. The approach automatically monitors the free surface, whereby the monitoring of the resin front migration using e.g. levelset or front tracking control is completely avoided. The proposed formulation of the manufacturing infusion has been implemented and used for both LRI and RTM simulations, and numerical results are provided for a hat stringer problem.To complete the manufacturing process chain, the curing step is considered in the present contribution as a simple thermal shrinkage problem, whereby the fiber content obtained from the LRI or RTM–simulations is used for the evaluation of residual stresses and component distortion.
|
|
| 28. |
- Rouhi, Mohammad Sadegh, 1983, et al.
(författare)
-
MODELING THE CONSTITUTIVE RESPONSE OF AN ANISOTROPIC DUAL-SCALE FLOW
- 2012
-
Ingår i: 11th International Conference on Flow Processing in Composite Materials (FPCM11) - Auckland - New Zealand 2012.
-
Konferensbidrag (refereegranskat)abstract
- Today’s trend in composites manufacturing is to reduce cost by, among other things, cutting down the number of operations required to produce a component. For example all the steps of impregnation the reinforcement, consolidation, forming and finally curing may be, in some cases, combined into a single processing operation. This leads to increasingly complex manufacturing processes with many interacting sub-processes occurring simultaneously on different spatial and temporal scales. In this context we are developing an unified finite-strain continuum framework [1],[2],[3],[4], which we recently adopted towards modeling of dual-scale flows in composite manufacturing [5]. In this context, in the present work we consider the manufacturing of the so called Engineering Vacuum Channel (EVaC) prepreg materials as discussed in e.g. [6]. Even though our numerical framework is capable of modeling all the interacting sub-processes at ones, the constitutive models for these are still rare and have not been generalized in a proper continuum context. In summary, the idea of the present work is to emanate from the existing model for fluid follow in a rectangular channel (the so called Poiseuille flow) and generalize it in the finite-strain continuum context. The major task is then to extend our framework to account for anisotropic Darcian interaction on the macro scale and implement the constitutive model into it, while the minor task is to examine the interaction between preform deformation on different scales and the process of micro infiltration and macro flow. The major task is accomplished by introducing the anisotropic permeability model to our coupled displacement-pressure, non-linear finite element model, while the minor task is approached using a representative numerical example, displaying the relevant interactions between the involved sub-processes. The algorithm is then tested for drained conditions, and results are compared to the one in [5] for isotropic flow.
|
|
| 29. |
|
|
| 30. |
|
|
| 31. |
- Rouhi, Mohammad, et al.
(författare)
-
SIMULATION OF 3D PREPREG CONSOLIDATIONPROCESS USING SOLID SHELL ELEMENTS
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
| 32. |
- Rouhi, Mohammad, et al.
(författare)
-
SIMULATION OF 3D RTM PROCESS USING SOLID SHELL ELEMENT
- 2016
-
Ingår i: 13th International Conference on Flow Processes in Composite Materials (FPCM 13).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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
|
|
| 33. |
- Saseendran, Sibin, et al.
(författare)
-
Characterisation of Viscoelastic Material Properties During Curing Processes
- 2016
-
Ingår i: Challenges in Mechanics of Time Dependent Materials. - Cham : Encyclopedia of Global Archaeology/Springer Verlag. - 9783319224428 - 9783319224435 ; , s. 45-54
-
Konferensbidrag (refereegranskat)abstract
- The present contribution is toward systematic characterisation of the thermo-viscoelastic properties of a curing epoxy resin system. Characterising the viscoelastic solid behaviour is performed using a dynamic mechanical analyser. The aim of this work is to investigate the dependence of the viscoelastic response on time, temperature and degree of cure and to derive a model that covers the dependency of the relaxation modulus on all three factors and also to investigate how various factors would influence each other in the overall evolution of the relaxation modulus. In particular, we investigate the linearity between the three factors above. To summarize, the results indicate that these three parameters indeed obey a linear relationship.
|
|
| 34. |
- Saseendran, Sasha, et al.
(författare)
-
Characterisation of viscoelastic material properties during curing processes
- 2015
-
Ingår i: ICCM International Conferences on Composite Materials. - : International Committee on Composite Materials. ; 2015-July
-
Konferensbidrag (refereegranskat)abstract
- The present contribution is toward systematic characterisation of the thermo-viscoelastic properties of a curing epoxy resin system, here we use Huntsman LY5052/HY5052 as model material. The main focus is to verify the existence of equivalence relation (linearity) between time, temperature and degree (time) of cure. As a starting point, the cure kinetics behaviour of the model material has been characterised using DSC equipment and the results have been used to identify parameters in a generic Kamal cure kinetics model. In the subsequent work the DSC data and Kamal model was used to carefully monitor the degree of cure in the resin in all the subsequent experiments. The thermo-viscoelastic response of the curing epoxy was characterised using a dynamic mechanical thermal analyser (DMTA). All the DMTA experiments were focused on rubbery and glassy states only, were the material was subject to tests at various isothermal and non-isothermal loading conditions. The results were used to investigate the linearity between the three factors above (time, temperature and curing time). To summarize, the results indicate that these three parameters indeed obey a linear relationship in the linear viscoelastic regime.
|
|
| 35. |
- Saseendran, Sibin, et al.
(författare)
-
Cure-state dependent viscoelastic Poisson’s ratio of LY5052 epoxy resin
- 2017
-
Ingår i: Advanced Manufacturing: Polymer and Composites Science. - : Taylor and Francis Ltd.. - 2055-0359 .- 2055-0340. ; 3:3, s. 92-100
-
Tidskriftsartikel (refereegranskat)abstract
- It is shown, using thermodynamically consistent linear viscoelastic material model that accounts for properties dependence on test temperature and cure state parameters, that for rheologically simple materials the cure and temperature related reduced times and shift factors are the same for all viscoelastic compliances, relaxation modulus, and Poisson’s ratio as well as for the storage and loss modulus. A necessary condition for that is that the cure and temperature parameters are affecting the reduced time only. This means that the Poisson’s ratio of polymeric materials, which for simplicity is often assumed constant, in fact exhibits a small dependence on time which is affected by temperature and state of cure. In this work, the evolution of the viscoelastic Poisson’s ratio of the commercial LY5052 epoxy resin is studied in relaxation test subjecting the specimen to constant axial strain. Specimens at several cure states are studied and Poisson’s ratio, defined as the lateral and axial strain ratio, is shown to evolve from 0.32 to 0.44 over time. Moreover, the data confirm that the cure state-dependent reduced time controlling the Poisson’s ratio development leads to the same shift functions as those identified in DMTA tests for storage modulus. The latter measurements also confirmed that the total shift can be considered as a sum of two shifts in the frequency domain, which means that function for reduced time calculation can be written as a product of two functions: one dependent on the test temperature and another one dependent on the cure state.
|
|
| 36. |
- Saseendran, Sibin, 1989-, et al.
(författare)
-
Effect of degree of cure and time on viscoelastic poisson's ratio
- 2017
-
Ingår i: ICCM21 Proceedings. - : ICCM, International Committee on Composite Materials.
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 37. |
- Saseendran, Sibin, 1989-, et al.
(författare)
-
Evolution of viscoelastic behavior of a curing LY5052 epoxy resin in the glassy state
- 2016
-
Ingår i: Advanced Manufacturing: Polymer & Composites Science. - : Taylor & Francis. - 2055-0340 .- 2055-0359. ; 2:2, s. 74-82
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this work is to develop a methodology to analyze the influence of the curing history on the viscoelastic storage modulus. Two different experimental approaches are presented exposing the material to various cure temperature and cure time sequences. The evolving viscoelastic properties are characterized using standard Dynamic Mechanical and Thermal Analysis (DMTA) equipment. Therefore, the present study is limited to infinitesimally small strains and linear viscoelasticity only. The methodology is demonstrated using the LY5052 epoxy resin system for its storage modulus E′ in the frequency domain. Results indicate that evolution of thermo-viscoelastic properties could be indeed assumed independent of the cure history for the investigated LY5052. We observe that the shift factor in the reduced time expression for the viscoelastic model examined in this paper is a product of two shift functions, namely the temperature and cure shift functions.
|
|
| 38. |
- Saseendran, Sibin, 1989-, et al.
(författare)
-
Evolution of viscoelastic behaviour of a curing LY5052 epoxy resin in the rubbery state
- 2017
-
Ingår i: Advanced Composite Materials. - : Informa UK Limited. - 0924-3046 .- 1568-5519. ; 26:6, s. 553-567
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 39. |
- Saseendran, Sibin, 1989-, et al.
(författare)
-
Viscoelastic behavior of LY5052 epoxy resin in rubbery state during curing
- 2016
-
Ingår i: ECCM 2016 - Proceeding of the 17th European Conference on Composite Materials. - : European Conference on Composite Materials, ECCM. - 9783000533877
-
Konferensbidrag (refereegranskat)abstract
- The aim of the presented work is to investigate the relationship between the rubbery modulus and the degree of cure for partially to fully cured LY5052 epoxy resin. In particular, this work experimentally tests an existing model defined in shear modulus by redefining into the elastic tensile modulus. Experiments were performed in a Dynamic Mechanical and Thermal Analysis (DMTA) machine in the frequency domain. After the model is tested, super-master curves generated using time-temperature-cure superposition are normalized using the model so that the rubbery modulus made independent on the state of cure, which further simplifies the super-master curves. This results in a unique master curve that describes the viscoelastic behavior of the LY5052 epoxy resin for the given conditions. This consequently could help formulate simplified models to predict viscoelastic behaviour and also develop better experimental methodologies to characterize them.
|
|
| 40. |
|
|
| 41. |
- Szpieg, Magdalena, et al.
(författare)
-
Development and characteristics of a fully recycled CF/PP composite
- 2012
-
Konferensbidrag (refereegranskat)abstract
- A fully recycled carbon fibre reinforced polypropylene (rCF/rPP) composite material has been developed and characterised. This new, randomly oriented short fibre composite was manufactured by press forming with a fibre volume fraction of 40 %. A series of tensile tests using rectangular specimens cut in four different directions (0°, 90°, ±45°) in the composite plate were performed to confirm in-plane material isotropy. Models to predict stiffness and strength of the short fibre rCF/rPP composite were also employed and validated using experiments. To model the viscoelastic and viscoplastic responses of the composite, an inelastic material model was employed and characterised using a series of creep and recovery tests. From the creep tests, it was found that the time and stress dependence of viscoplastic strains follows a power law. The viscoelastic response of the composite was found to be linear in the investigated stress range. The material model was validated in constant stress rate tensile tests and the agreement was good, even close to the rupture stress.
|
|
| 42. |
- Szpieg, Magdalena, et al.
(författare)
-
Mechanical performance and modelling of a fully recycled modified CF/PP composite
- 2012
-
Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 46:12, s. 1503-1517
-
Tidskriftsartikel (refereegranskat)abstract
- A fully recycled carbon fiber reinforced maleic anhydride grafted polypropylene (MAPP)-modified polypropylene (rCF/rPP) composite material has been developed and characterized. This new composite was manufactured employing papermaking principles, dispersing the recycled carbon fibers (rCF) in water, and forming them into mats. Two layers of the recycled polypropylene (rPP) films manufactured using press-forming were sandwiched between three rCF preform layers in a stack. The stack was heated and press-formed resulting in a composite plate with a nominal thickness of 1.20 mm and a fiber volume fraction of 40%. A series of tensile tests using rectangular specimens cut in four different directions (0°, 90°, ± 45°) in the composite plate were performed to confirm in-plane material isotropy. Models to predict stiffness and strength of the short fiber rCF/rPP composite were also employed and validated using experiments. The models were found to be in good agreement with experimental results. Fiber length distribution measurements were performed before (unprocessed) and after (processed) composite manufacturing to investigate the influence of processing on fiber degradation. The results revealed a significant reduction in fiber length by the press-forming operation. To model the viscoelastic and viscoplastic responses of the composite an inelastic material model was employed and characterized using a series of creep and recovery tests. From the creep tests, it was found that the time and stress dependence of viscoplastic strains follows a power law. The viscoelastic response of the composite was found to be linear in the investigated stress range. The material model was validated in constant stress rate tensile tests and the agreement was good, even close to the rupture stress. © The Author(s) 2011.
|
|
| 43. |
- Szpieg, Magdalena, et al.
(författare)
-
Novel composites from recycled constituents
- 2009
-
Ingår i: 24th annual technical conference of the American Society for Composites 2009 and 1st Joint Canadian-American Technical Conference on Composites. - Red Hook, NY : Curran Associates, Inc.. - 9781615676033 ; , s. 2651-2661
-
Konferensbidrag (refereegranskat)abstract
- Only a small fraction of the waste generated by use and manufacturing of carbon-based composites is currently reused. However, due to European Union (EU) regulations and limited amount of landfilling, the industry is forced to consider recycling solutions already during the manufacturing process. The following work is devoted to the development of a technique for manufacture of novel engineering materials from recycled carbon fibres and thermoplastic matrix. Fibre preforms are manufactured employing a papermaking technique for dispersing the carbon fibres. The polypropylene (PP) matrix was reprocessed into a film. The carbon fibre preforms and PP films were stacked and composite materials were subsequently manufactured by press forming and evaluated.
|
|
| 44. |
- Szpieg, Magdalena, et al.
(författare)
-
Recycled polypropylene aimed as composites precursor material
- 2009
-
Ingår i: Plastics, rubber and composites. - 1465-8011 .- 1743-2898. ; 38, s. 412-418
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this research is to assess the stability and processability of recycled polypropylene (PP) materials for their suitability for use as matrix material in polymer composite. The work comprises development and characterisation of matrix precursors from recycled PP. The reused PP considered comes from two sources: PP from the self-reinforced PP Pure processing scrap and an automotive grade developed to offer an even material quality. To assess the thermal stability of two PP qualities for subsequent composite manufacturing, oxidation induction time (OIT), melting point Tm, decomposition temperature 7d and viscosity μ were investigated. The results indicate, that Pure processing scrap is very well stabilised and therefore suitable for multiple processing, whereas the automotive grade recycled PP cannot be used for this purpose. Fibres for subsequent composite preforming were spun by melt spinning from the Pure scrap processing and its mechanical properties were characterised. © Institute of Materials, Minerals and Mining 2009.
|
|
| 45. |
- Szpieg, Magdalena, et al.
(författare)
-
Reuse of polymer materials and carbon fibres in novel engineering composite materials
- 2009
-
Ingår i: Plastics, rubber and composites. - 1465-8011 .- 1743-2898. ; 38:9-10, s. 419-425
-
Tidskriftsartikel (refereegranskat)abstract
- The present work was devoted to the development of a technique for manufacture of a novel engineering material from carbon fibres and thermoplastic matrix recyclates. Fibre preforms were manufactured employing a papermaking technique for dispersing the carbon fibres. The polypropylene (PP) matrix recyclate was reprocessed into a film. The carbon fibre preforms and PP films were stacked and composite materials were subsequently manufactured by press forming. The mechanical behaviour of carbon fibre preforms was characterised by a compaction test and compared to the results obtained by consolidation test of the carbon fibres reinforced PP composites. The consolidation experiments were found to follow the trend from compaction tests allowing prediction of the amount of polymer material needed, fibre volume fraction as well as composites thickness. The resulting dispersion of fibres and void content were evaluated by microscopy.
|
|
| 46. |
- Toll, Staffan, 1964, et al.
(författare)
-
Process rheology of fibre composites
- 2005
-
Ingår i: Proc. Nordiska Polymerdagarna, August 17-19, Gothenburg, Sweden.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 47. |
- Wysocki, Maciej, 1969, et al.
(författare)
-
Anisotropic and tension-compression asymmetric model for composites consolidation
- 2010
-
Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 41:2, s. 284-294
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 48. |
- Wysocki, Maciej, et al.
(författare)
-
Consolidation of commingled yarn based composites : continuum modelling
- 2007
-
Ingår i: Proceedings of COMP07.
-
Konferensbidrag (refereegranskat)abstract
- Pressure driven consolidation of a component made from a commingled yarn composite is modelled and simulated. A finite-element code is developed based on a novel two-phase continuum framework. The applicability of the code to complex geometries is demonstrated by analysis of the consolidation, i.e. resin infiltration and preform deformation, of an axisymmetric filament wound GF/PP pressure vessel. In conclusion, the consolidation of the vessel is prevented by the loading mode where the pressure is applied on the interior. To succeed in manufacturing of this type of pressure vessel, a use of an loosely wound preform that allows extension in the fibre direction is suggested.
|
|
| 49. |
|
|
| 50. |
- Wysocki, Maciej, et al.
(författare)
-
Constitutive models for transversely isotropic fibreprefrom in composite manufacturing
- 2016
-
Ingår i: 13th International Conference on Flow Processes in Composite Materials (FPCM 13).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- 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.
|
|
