S.T. Pinho

Recycling carbon fibre reinforced polymers for structural applications: Technology review and market outlook

Both environmental and economic factors have driven the development of recycling routes for the increasing amount of carbon fibre reinforced polymer (CFRP) waste generated. This paper presents a review of the current status and outlook of CFRP recycling operations, focusing on state-of-the-art fibre reclamation and re-manufacturing processes, and on the commercialisation and potential applications of recycled products. It is shown that several recycling and re-manufacturing processes are reaching a mature stage, with implementations at commercial scales in operation, production of recycled CFRPs having competitive structural performances, and demonstrator components having been manufactured. The major challenges for the sound establishment of a CFRP recycling industry and the development of markets for the recyclates are summarised; the potential for introducing recycled CFRPs in structural components is discussed, and likely promising applications are investigated.

Material and structural response of polymer-matrix fibre-reinforced composites: Part B

This article showcases the authors’ predictions for Part B of the second World Wide Failure Exercise. Predictions are made using the failure criteria published in the submission for Part A. In several cases, the original predictions are found to match the experimental data well and no revisions are made. A novel constitutive model for unidirectional composite materials is used to improve predictions for cases involving multidirectional laminates.

Numerical simulation of the crushing process of composite materials

Abstract Components in composite materials are progressively replacing metals for crashworthy applications in the automotive, railway and aeronautical industries. The numerical simulation of the crushing process for composite structures is a recent research area. Due to the complex mechanical behaviour of advanced composites, the capability of the existing analytical and numerical models to predict the crushing behaviour of composite materials is still limited. A numerical model for the crushing simulation of fibre-reinforced composite materials is proposed in this work. The progression of the main cracks is modelled using a new formulation of finite decohesion elements, that allows to correctly account for the energy involved in the cracking process. The intralaminar damage is modelled taking into account the specificities of each material system, degrading the elastic properties in accordance with the different predicted physical damage phenomena. After the validation of the decohesion element, this is used as part of a model for simulation of composite tubes crushing. A good agreement between the numerical results and the experimental data is achieved. The need for further improvements on the physical basis of the intralaminar failure criteria used, as well as on the numerical solution methods for the non-linear problem, is identified.

On longitudinal compressive failure of carbon-fibre-reinforced polymer: from unidirectional to woven, and from virgin to recycled

Modelling the longitudinal compressive failure of carbon-fibre-reinforced composites has been attempted for decades. Despite many developments, no single model has surfaced to provide simultaneously a definitive explanation for the micromechanics of failure as well as validated predictions for a generic stress state. This paper explores the reasons for this, by presenting experimental data (including scanning electron microscopic observations of loaded kink bands during propagation, and brittle shear fracture at 45° to the fibres) and reviewing previously proposed micromechanical analytical and numerical models. The paper focuses mainly on virgin unidirectional (UD) composites, but studies for woven and recycled composites are also presented, highlighting similarities and differences between these cases. It is found that, while kink-band formation (also referred to in the literature as microbuckling) is predominant in UD composites under longitudinal compression, another failure mode related to the failure of the fibres can be observed experimentally. It is also shown that the micromechanics of the failure process observed in UD composites is similar to that in other fibre architectures, hence encouraging the adaptation and application of models developed for the former to the latter.

Combining damage and friction to model compressive damage growth in fibre-reinforced composites

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.

Response and damage propagation of polymer-matrix fibre-reinforced composites: Predictions for WWFE-III Part A

This paper showcases the authors’ predictions for the 13 challenging test cases of the third World Wide Failure Exercise. The cases involve the prediction of lamina biaxial stress–strain curves, matrix cracking and delamination in various cross-ply and quasi-isotropic laminates under uniaxial loading, variation of thermal expansion coefficient of a laminate with matrix cracking, bending of a general laminate, loading-unloading behaviour and the strength of various thin and thick laminates containing an open hole. The laminates were made of various glass and carbon fibre/epoxy materials. The constitutive model is based on plasticity theory, includes hydrostatic pressure effects and accounts for multiaxial load combination effects. The failure criteria distinguish between matrix failure, fibre kinking and fibre tensile failure. In-situ strengths are used for matrix failure. Propagation of failure takes into consideration the fracture energy associated with each failure mode and, for matrix failure, the accumulation of cracks in the plies. The model is used to make blind predictions of all test cases from the third World-Wide Failure Exercise.

Stochastic failure modelling of unidirectional composite ply failure

Stochastic failure envelopes are generated through parallelised Monte Carlo Simulation of a physically based failure criteria for unidirectional carbon fibre/epoxy matrix composite plies. Two examples are presented to demonstrate the consequence on failure prediction of both statistical interaction of failure modes and uncertainty in global misalignment. Global variance-based Sobol sensitivity indices are computed to decompose the observed variance within the stochastic failure envelopes into contributions from physical input parameters. The paper highlights a selection of the potential advantages stochastic methodologies offer over the traditional deterministic approach.

A coupled mixed-mode delamination model for laminated composites

Cohesive elements have now become commonplace in many commercial finite element codes. Their use in impact and crash and other complex composite design problems requires the development of more advanced cohesive element formulations capable of predicting mixed-mode behavior during a complex loading. A cohesive zone model is developed for the simulation of delaminations in laminated composites under mixed-mode loadings, based on a coupling between the normal and tangential components of the relative displacement across an interlaminar interface. Featuring a unique characterization of degraded states, this coupling enables a simultaneous loss of loading capacity of the interface in normal and tangential directions, once the criteria on delamination growth are satisfied. Moreover, the variation of mode participation during the delamination process is effectively considered. A comparison between numerical simulations and experimental data on typical delamination tests shows the robustness and the potential of the model.

A Numerical Material Model for Predicting the High Velocity Impact Behaviour of Polymer Composites

This paper describes key features of an advanced, physically-based, numerical material model for predicting the static and dynamic, failure and damage, response of polymer matrix composites with fibrous UD plies. The model has been implemented into the explicit Finite Element code LS-DYNA3D for solid brick elements with one integration point.

Mechanical response of composites

1 Computational Methods for Debonding in Composites, by Rene de Borst and Joris J.C. Remmers 2 Material and Failure Models for Textile Composites, by Raimund Rolfes, Gerald Ernst, Matthias Vogler and Christian Huhne 3 Practical Challenges in Formulating Virtual Tests for Structural Composites, by Brian N. Cox, S. Mark Spearing and Daniel R. Mumm 4 Analytical and numerical investigation of the length of the cohesive zone in delaminated composite materials, by Albert Turon, Josep Costa, Pedro P. Camanho and Pere Maimi 5 Combining elastic brittle damage with plasticity to model the non-linear behavior of fiber reinforced laminates, by Clara Schuecker and Heinz E. Pettermann 6 Study of delamination in composites by using the serial parallel mixing theory and a damage formulation, by Xavier Martinez, Sergio Oller and Ever Barbero 7 Interaction Between Intraply and Interply Failure in Laminates, by F.P. van der Meer and L.J. Sluys 8 A Numerical Material Model for Predicting the High Velocity Impact Behaviour of Polymer Composites, by Lucio Raimondo, Lorenzo Iannucci, Paul Robinson and Silvestre T. Pinho 9 Progressive Damage Modeling of Composite Materials under both Tensile and Compressive Loading Regimes, by N. Zobeiry, A. Forghani, C. McGregor, R. Vaziri and A. Poursartip 10 Elastoplastic Modeling of Multi-phase Metal Matrix Composite with Void Growth using the Transformation Field Analysis and Governing Parameter Method, by Ernest T.Y. Ng and Afzal Suleman 11 Prediction of Mechanical Properties of Composite Materials by Asymptotic Expansion Homogenisation, by J.A. Oliveira, J. Pinho-da-Cruz and F. Teixeira-Dias 12 On Buckling Optimization of a Wind Turbine Blade, by Erik Lund and Leon S. Johansen 13 Computation of Effective Stiffness Properties for Textile-Reinforced Composites Using X-FEM, by M. Kastner, G. Haasemann, J. Brummund and V. Ulbricht 14 Development of Domain Superposition Technique forthe Modelling of Woven Fabric Composites, by Wen-Guang Jiang, Stephen R. Hallett and Michael R. Wisnom 15 Numerical Simulation of Fiber Orientation and Resulting Thermo-elastic Behavior in reinforced Thermo-plastics, by H. Miled, L. Silva. J.F. Agassant and T. Coupez