Interfacial damage and load transfermodeling in short fiber reinforced composites

Due to the compromise between their thermomechanical properties and low density, Short Fiber Reinforced Polyamides (SFRP) present a good alternative to metals for automotive structural components. The microstructure of such materials, combined with the matrix sensitivity to environmental conditions, has a strong impact on their overall behavior and the related damage. A new multi-scale modelling strategy is proposed, based on the experimental observations of interfacial damage evolution for PA66-GF30 composites. Three main key-points have been integrated to this approach: an original damage evolution law at the interface, an appropriate load transfer law at the matrix-fiber interface, and a homogenization strategy founded on the generalized Mori-Tanaka scheme. The damage evolution law is driven by a local probabilistic criterion based on the interfacial stress field estimation. This type of evolution depends on the maximal local damage rate at the fiber/matrix interface, determined from a numerical evaluation at several points of the interface surrounding the inclusion. It is then coupled with a load transfer law formulated according to a modified shear lag model (SLM). The developed model is assessed with a finite element (FE) computation integrating cohesive elements at the matrix-fiber interface. The FE unit cell consists in a periodic media (hexagonal array) with periodic boundary conditions. The fiber-matrix interface integrates cohesive elements, with a cohesive law driven by a Paulino-Park-Roesler (PPR) potential-based formulation. The latter has been proven to be suitable for the 3D modeling of interface in reinforced composites. The proposed approach is able to accurately capture the non-linear behavior of short fiber reinforced polyamide composites accounting for interfacial damage.FUI project Durafip, driven by Dr. Gilles Robert of Solvay Engineering Plastic