Acoustic emission on failure analysis of rubber-modified epoxy resin

Rubber-modified epoxy resins have been employed as adhesive and matrix materials for glass and corbon-fiber composites. The behavior of fracture around a crack tip for rubber-modified epoxy resin is investigated through the acoustic emission (AE) analysis of compact tension specimens. Damage zone and rubber particles distributed around a crack tip were observed by a polarized optical microscope and an atomic force microscope (AFM). The damage zone in front of pre-crack tip in rubber-modified specimen (15 wt% rubber) began to form at about 13 % level of the fracture load and grew in size until 57 % load level. After that, the crack propagated in a stick-slip manner. Based on time-frequency analysis of AE signals and microscopic observation of damage zone, it was thought that AE signals with frequency bands of 0.15–0.20 MHz and 0.20–0.30 MHz were generated from cavitation in the damage zone and crack propagation, respectively.