A novel trans-scale method for predicting mode I matrix crack density of composite laminates

Abstract

Permeability of linerless composite cryogenic tanks has positive correlation with matrix micro-crack density. In order to obtain the mode I matrix micro-crack density of fiber-reinforced plastic-matrix composite laminates, this paper proposes a novel trans-scale method that the macro-mechanical stress analysis is independent from micro-mechanical stiffness degradation in the computational process. The micro-mechanical model of a representative volume element (RVE) which contains a matrix micro-crack is established for stiffness degradation analysis. Then, the fracture critical normal and shear stresses on the micro-scale are gained via energy analysis of the RVE that contains a mode I or mode II matrix crack. The critical stresses on the macroscopic structure versus matrix crack density are established by the energy balance between the RVE contains a micro-crack and the RVE without any cracks. Therefore, the macro-mechanical stress distribution can be used to determine mode I and mode II matrix crack densities of composite laminates respectively. Numerical examples of glass-fiber/epoxy composite laminates in which mode I micro-cracks are dominant are in good agreement against available experiments. The trans-scale mode I matrix crack density prediction method has significance of the leakage resistance design for linerless composite tanks or other composite laminated structures.