Micromechanical analysis of strain rate effect on damage evolution in sheet molding compound composites

Analysing the damaged elastic behaviour of composite materials subjected to dynamic loading requires an investigation of the strain rate influence on the damage mechanisms initiation and evolution. Low and high-speed tensile tests (epsilon less than or equal to 200 s(-1)) coupled to SEM observations were conducted upon a sheet molding compound composite (SMC-R26). The results of the developed experimental approach contributed to analyse the strain rate effects. at microscopic and macroscopic material scales, on the overall behaviour and damage growth. It was shown that the strain rate mainly governs the damage threshold and accumulation. This yields to a mechanical behaviour accommodation corresponding to an increase of the ultimate strain and stress. Mainly, this work has established the visco-damaged nature of the non-linear behaviour under a moderate dynamic loading. (C) 2004 Elsevier Ltd. All rights reserved.