A model for the prediction of transverse crack and delamination density based on a strength and fracture mechanics probabilistic approach

Abstract

The aim of this study is to provide a relevant description of damage growth and the resultant network for leakage prediction in liner-less composite vessels. A damage meso-model built on strength and energy criteria as proposed in FFM (Finite Fracture Mechanics) is introduced. Both criteria have to be fulfilled for the creation of the first transverse crack of the RVE (Representative Volume Element). The increase of crack density and the propagation of micro-delamination at crack tips are managed by Fracture Mechanics using the energy release rate. In this way the effect of ply thickness is explicitly accounted. The energy release rate at the meso-scale (RVE scale) is calculated from a multiscale approach. Numerical results show that, in [0 2 /90 1 /0 2 ] and [0 2 /90 3 /0 2 ] lay-ups under tensile stress, no delamination should occur for values of the energy release rates from the literature. This conclusion is reinforced by cross-section examinations through the width of specimens submitted to tensile loading. Delamination almost disappears after removing a few microns of the surface. Experimental results also highlight a preliminary step in the damage scenario with small cracking rate, likely driven by weak areas (defects locations). The modelling of this step being fundamental for the prediction of first leak paths, it was introduced througha probabilistic approach.