Experimental investigations of spontaneous bimaterial interfacial fractures

Following our innovative experimental spontaneous fracture models for frictional fractures (compression and shear) and mixed-mode fractures (tension and shear) in identical materials, we designed a laboratory model to investigate the effects of material contrast on mixed-mode spontaneous fracture along a bimate-rial interface. A series of interesting phenomena are observed, including asymmetry of crack propagation, with different speeds and levels of fracture parameters. Crack tips fracture parameters are observed to depend on crack speeds, on far-field loading, and on far-field mode-mixity. A strong dependence is also identified between mode-mixity and crack length. Most importantly, the fracture parameters are found to exhibit a strong dependence upon crack length and only a weak dependence on crack speed as is commonly thought. These observations are discussed in details in relation to material contrast. It is expected that these observations will have a profound influence on engineering practice involving the application of materials and structures with bimaterial interfaces.