Multiscale modelling of matrix-crack percolation and gas leakage in fibre-reinforced composites

A multiscale framework is presented for predicting matrix-crack percolation and gas leakage in fibre-reinforced composites without empirical calibration. By eliminating fitting parameters, the approach provides clear advantages over existing models. A new continuum formulation enriched by a micromechanical damage model is first developed to predict matrix-crack spacing in individual plies, overcoming the dependence of conventional methods on destructive experimental measurements. By explicitly analysing fibres, matrix, and fibre-matrix interfaces, the formulation significantly reduces input requirements to a small set of constituent properties obtainable through standardized testing. The outputs are subsequently upscaled into a laminate-level continuum damage mechanics model to determine matrix-crack spacing as a function of applied strain. This crack-spacing information defines the geometry of a representative unit-cell model used to quantify throat areas at crack intersections. Unlike previous approaches that assume arbitrary delamination lengths, the present framework provides a physically based determination of throat areas. These micro-meso scale predictions are then coupled with an orifice flow model to enable complete leak-rate prediction of macroscale structures without empirical inputs. This novel multiscale framework is shown to accurately reproduce experimental leakage data. Its capability for design and certification of cryogenic fuel storage vessels is demonstrated by quantifying the benefit of increased matrix toughness in enhancing resistance to gas leakage.