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A numerical study into the rate-dependent failure behaviour of unidirectional carbon fiber reinforced polyvinylidene fluoride
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A novel composite material that is used in offshore energy transport is carbon fiber reinforced polyvinylidene fluoride (PVDF). The PVDF matrix is used because of its outstanding chemical resistance and beneficial thermal properties, whereas the carbon fibers provide high strength and stiffness. Due to this novel combination of constituents, the critical failure mechanisms need to be studied. In this study, the response of unidirectional carbon fiber reinforced PVDF is investigated by performing uniaxial compression and tensile experiments on unidirectional composite samples at different constant applied strain rates for various temperatures. Furthermore, the influence of the fiber orientation with respect to the loading direction is varied. Both compression and tensile tests show the rate- and temperature-dependent response of the composite, which is attributed to the PVDF matrix [1]. Transverse tensile loading experiments show a low tensile strength of the composite compared to the neat PVDF matrix. Post-mortem investigation of the specimens revealed that the low transverse tensile strength is caused by weak adhesion between the fiber and the matrix. To better understand, and possibly predict, the rate-dependent response of unidirectional carbon fiber reinforced PVDF at different temperatures, a micromechanical finite element (FE) model is used. Based on microscopic scans of a cross-section of the unidirectional composite, a 3-dimensional representative volume element (RVE) is generated, consisting of a number of fibers embedded in a matrix. The nonlinear rate-dependent response of the PVDF matrix is modelled using an elasto-viscoplastic constitutive model that can accurately describe the rate-dependent behaviour of PVDF under different loading conditions at different temperatures [2]. Cohesive zone elements are used to model the weak adhesion between the fiber and the matrix. The constitutive response of the cohesive elements is described by a traction separation law. Periodic boundary conditions are applied to prescribe a macroscopic deformation to the RVE, similar to the experimental loading conditions. Comparison of the results from the FE-simulations to the experiments, shows that the micromechanical model can adequately describe the non-linear rate-dependent response of the composite material at different temperatures. Furthermore, the influence of the fiber orientation with respect to the loading direction is captured, requiring only a relatively