Multi-scale analysis of the mechanical behaviour of a flax fibre reinforced composite under low-velocity impact

Abstract

The use of biocomposite materials in different fields requires enhanced knowledge of the nonlinear phenomena related to their complex mechanical behaviour. Namely, nonelastic mechanisms such as damage, plasticity, and rupture, potentially coupled with viscosity incidence, affect the structure’s lifetime. In this context, the aim of this paper is to propose a simplified and accessible approach that leads to modelling the overall mechanical behaviour of the composite material. The studied laminate composites were made of thermoplastic Elium resin reinforced with flax plies. Experimental quasistatic and dynamic characterisations were conducted via tensile and cyclic tensile tests to investigate the structure’s mechanical properties and corresponding failure mechanisms. The test results clearly demonstrated the presence of significant nonlinear specific coupling effects due to both flax fibre and Elium resin. The proposed multi-scale modelling analysis assumes two principal entities: the ply constituted by one or more layers of unidirectional fibres and the fibre-matrix interface considered as a surface layer of resin. Each entity was characterized by specific damage variables that were determined by mechanical tests. Model parameters were experimentally identified and expressed in the behaviour model to simulate the composite structure subjected to low-velocity impact using the Pam-Crash F.E. numerical code.