Fracture Behavior of Heavily Cross-Linked Epoxy: Testing, Fractography, and Numerical Modeling

Heavily cross-linked epoxy was characterized under different types of loading. The scope of work involves detailed testing procedures utilizing high-precision digital image correlation (DIC) system for all strain measurements. Fractographic analyses using scanning electron microscopy (SEM) were also provided. Besides, computed tomography (CT) scans were employed to characterize existing manufacturing imperfections, i.e., voids. Numerical modeling using extended finite element method (XFEM) utilizing the actual microstructure is conducted. Testing results and fractographic analyses showed that microvoids led to failure initiation at micro lengths. An unstable fracture behavior dominated the final failure under different types of loading. Global plastic deformation was observed in the case of uniaxial tension, while local plasticity was observed in specimens under three-point loading. It can be concluded that epoxies failure under a combined state of stresses is sophisticated, and straightforward stress/strain-based failure criteria are not well-suited for failure predictions.