Prediction and optimization design for thermal expansion coefficients of three-dimensional n-directional-braided composites

A new model based on thermomechanics analysis is established to predict the coefficients of thermal expansion (CTEs) of 3D n-directional (n = 4, 5, full-5, 6, or 7)-braided composites in this article. In this model, relationships between stresses and strains generated in fiber and polymer matrix are portrayed by a bridging matrix to obtain elastic constants of yarns. Based on equivalent fiber cross-sections and space projections of yarns, effective overall CTEs of 3D n-directional-braided composites are obtained. We introduce parameterization into the finite element modeling to complete our verification. The theoretical predictions are consistent with the finite element method and existing experiments. This article gives detailed insights into the effect of braiding parameters on CTEs to explore indication of addition yarns for thermal expansion performance. As an application of the proposed model, we utilize an improved genetic algorithm with objective weight mechanism and dynamic mutation to obtain the multi-objective optimization design for zero expansion 3D-braided composites. (c) 2018 Society of Plastics Engineers POLYM. COMPOS., 40:2495-2509, 2019. (c) 2018 Society of Plastics Engineers