Dynamic and Static Fracture Toughness of Al/Epoxy Resin Interface

Abstract

Abstract This study evaluates the interfacial fracture strength and toughness of an epoxy resin/aluminum alloy based on two different tests of impact loading and quasi-static loading. In the impact test, we carried out the Laser Shock Adhesion Test (LaSAT). This method uses a strong ultrasonic wave induced by pulsed laser irradiation to induce interfacial fracture. Due to the grease layer ablation caused by laser irradiation, strong elastic wave generates and propagates. The tensile stress acts on the Al/epoxy resin interface, inducing an interfacial delamination. This delamination is further extended by an additional laser irradiation in order to evaluate the interfacial fracture toughness. By simulating the experimental delamination progression in FEM (Finite Element Method), we evaluated the dynamic fracture toughness of the Al alloy/epoxy resin interface. On the other hand, a quasi-static test for the toughness evaluation was conducted using a uniaxial tensile test. Before the tensile test, we produced an initial crack (initial delamination) at the interface by using laser ablation. Subsequently, this sample having initial crack is loaded by uniaxial tension. It is found that the interfacial crack progresses, resulting in unstable interfacial fracture. Furthermore, we conducted FEM simulation, in order to estimate the stress distribution near the delamination. By deriving a stress intensity factor from the stress distribution, we evaluated the quasi-static fracture toughness. To compare the dynamic and quasi-static fracture toughness of Al alloy/epoxy resin interface, we clarified the loading rate dependency of interfacial fracture toughness.