Experimental investigation of mode I fracture energy of adhesively bonded joints under impact loading conditions

Double cantilever beam (DCB) tests under impact loading conditions were conducted using a falling-wedge impact test machine and a high-speed camera. The change in mode I fracture energy G IC was investigated in comparison with the results obtained under the quasi-static loading condition. Two types of adhesives with significantly different mechanical properties were used for the DCB tests, and the change in rate dependency of the adhesive types was observed. Adhesively bonded joints have been widely used in various engineering products, such as automobiles, ships and airplanes. The strength of the joints is important for product safety. To evaluate the mode I fracture energy of adhesively bonded joints, DCB tests have been standardized under the quasi-static loading condition. Additionally, several tests have been proposed to evaluate the impact resistance of the joints. However, impact loading makes it difficult to evaluate the fracture energy accurately because of the dynamic effects. Therefore, specialized evaluation methods for dynamic fracture must be considered, and a load-independent analysis of the fracture energy was used to avoid load measurement problems due to the dynamic effects in this study.