Multiscale homogenization of thermo-mechanical viscoelastic response of 3D orthogonal composites with time-dependent CTEs

Abstract

Viscoelastic behavior of the matrix affects the thermomechanical response of polymer composites. This study investigated the structural effects of the time-dependent thermal expansion response of 3D orthogonal woven composite (3DOWC) by combining experiments and finite element modeling (FEM), incorporating the viscoelasticity of its constituents. The deformation characteristics at three orthogonal cross-sections, in the presence of structure-related strain fields at various temperatures, were investigated using digital image correlation method. Findings reveal heterogeneity and localization of the thermal strain, characterized by periodic stripes with alternating high strain regions on the resin and low strain regions on the yarn. This localization intensifies at higher temperatures, but diminishes with increased distance from the interface. Furthermore, the composites exhibit time-dependent thermal expansion behavior derived from the time-independent thermal expansion of its constituents, which cannot be captured in classic elastic material model. FEM reveals that thermal stresses are concentrated at the interfaces between constituents with significant differences in their coefficients of thermal expansion (CTE), particularly at the interface between the resins and axial yarns. The maximum thermal stress occurs in the binder yarns over the considered temperature range due to their low volume content, which should be considered in practical applications.