Anisotropic Visco-Elastoplastic Modeling of Quasi-Unidirectional Flax Fiber Reinforced Epoxy Behavior: An Investigation on Low-Velocity Impact Response

Based on experimental test results, flax fiber reinforced polymer composites are characterized by nonlinear visco-elastoplastic behavior. The aim of this work is to model the quasi-unidirectional flax fiber reinforced composite behavior through a three dimensional formulation with orthotropic elasticity and orthotropic plasticity using Hill criterion. The isotropic hardening and Johnson Cook parameters are identified from unidirectional tensile tests at different strain rates. The adjustment of Hill's yield criterion is developed based on yield stresses obtained in tensile tests at different directions. The numerical integration of the constitutive equations is implemented in a user-defined material, UMAT subroutines for the commercial finite element code ABAQUS. Once model parameters are identified using tensile tests, the model needs to be validated by confronting it with other experimental results. That is why experimental and numerical three-point bending tests are carried out in order to validate the proposed model with tests that have not served for the identification. Finally, a numerical parametric study on low velocity impact of a flax/epoxy composite circular plate is investigated.