Fracture Response of Cross-Linked Epoxy Resins as a Function of Loading Rate

Abstract

The failure behavior of cross-linked polymer epoxies were investigated under Mode I fracture at low and high loading rates. By varying the monomer choices, the properties of the epoxies can be tailored to achieve a greater resistance to cracking and high impact toughness. For these experiments, a unique four-point bending specimen was developed. High rate experiments were conducted on a modified Split Hopkinson Pressure Bar (SHPB) with pulse-shaping. High speed digital imaging was used to determine the failure initiation, and allow for use of digital image correlation (DIC) to optically measure the crack opening displacement (COD) and crack propagation velocity. The experimental results are used to obtain the energy required to initiate fracture at various loading rates. The critical energy required to initiate fracture for this epoxy shows limited rate dependence from quasi-static to dynamic loading rates, but becomes rate sensitive when loaded at dynamic rates. The experimental procedures and results are discussed in this paper.