Characterization of the Strain Rate-Dependent Deformation Response and Fracture Behaviour of a Three-Part Snap-Cure Epoxy Resin Under Tension and Compression Loading

The recent development of snap-curing epoxy resins and rapid manufacturing processes has led to increased usage of fiber-reinforced plastic composite materials in high-volume production vehicles. For energy absorbing composite structures, characterizing the epoxy strain rate-dependent response and local failure behaviour is critical to assess their crashworthiness performance. The current study investigated the tensile and compressive deformation response of a three-part snap-cure epoxy resin over a range of strain rates (i.e., \({10}^{-4} {\text{to}} {10}^{3} {{\text{s}}}^{-1}\) ${10}^{-4}\text{to}{10}^3{\text{s}}^{-1}$ ) using a suite of testing apparatuses. The average tensile elastic modulus, yield strength, and ultimate strength increased by 32%, 55%, and 49%, respectively, with increasing strain rate over the range considered. Tensile specimens fractured in a brittle manner despite deforming plastically, while fracture surface morphology was slightly influenced by the strain rate. The compressive elastic modulus was insensitive to increasing strain rate, while the compressive yield strength increased by 81% over the strain rates considered and was higher than the tensile yield strength at similar strain rates. This study addresses a critical gap in the literature by providing a comprehensive data set for a snap-cure epoxy material, which will support future development of a virtual multiscale-modeling framework aimed at predicting impact performance of composite automotive structures.