In-situ characterization and multiscale finite element analyses for thermomechanical behavior of 3D woven composites

Abstract

Thermal stress concentration, induced by the mismatch of coefficients of thermal expansion (CTE), contributes significantly to fatigue and failure of composites. We demonstrated the practicality of fiber Bragg grating sensors and high-resolution digital image correlation technique for in-situ characterization of thermal strain field evolution in 3D angle-interlocked woven composites (3DAWC). Multiscale representative volume element (RVE) models were constructed for studying its steady-state and transient-state thermomechanical behaviors. We found the CTE mismatch causes stress localization at the interface and it exhibits a periodic distribution within the 3DAWC, which attributes to its 3D architecture. Stresses and strains concentrate mainly on the sharp interfaces close to the diamond-shaped yarns and the resin-rich areas, respectively. The thermal stress in the resin reaches a maximum of 22 MPa around Tg, close to half of its yield stress. The macroscopic homogenized CTEs calculated from the RVE model in thickness and in warp directions are greater than those of each component. Transient analysis reveals that the non-uniform temperature field induced by heat transfer effects has little effect on maximum stress values in each component.