An integrated macro/micro-scale approach for in situ evaluation of matrix cracking in the polymer matrix of cryogenic composite tanks

Crack propagation in the matrix of composites is one of the major factors of propellant leakage in liner-less cryogenic composite tanks. In this paper, based on multi-scale finite element analysis strategy, an integrated macro/micro-scale (IMM) approach is developed to predict the failure of composite matrix by phase-averaging stress under cryogenic condition. In this model, the failure criterion of conventional maximum principal stress is improved by updating in situ strengths that is obtained by computing the stress concentration factors in a hexagonal representative volume element (AVE) under compression or transverse tension. Compared to other failure criteria, the predictions from this IMM approach agree with experimental results and can reflect the mismatch in coefficients of thermal expansion between different constituents. In addition, the impacts of materials systems and helical layups on the matrix cracking in composite tanks are also evaluated. This cross-scale method of IMM provides a powerful numerical tool for the reliability analysis of cryogenic composite tanks in complex working environments.