Study on Generalized Criteria of Interfacial Strength between Dissimilar Materials

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The purpose of this project is to establish the generalized fracture criteria for bonding interfaces. From the observation of damage process and fracture phenomena in bonding interface between dissimilar materials, interfacial damage model based on damage mechanics was developed. Then, by using this interfacial damage model to numerical simulations, the generalized fracture criteria of interfacial fracture were investigated. The mixed mode fracture tests were also conducted and the validity of this generalized fracture criteria was studied. The research results of this project are summarized as following,1. The cohesive zone model including loading histories and friction effect at the interface has been proposed.2. The numerical simulations for mixed fracture test under elastic and elastic-plastic analysis were carried out. Then, the fracture criteria based on the interfacial stress intensity factors can be describe as the elliptical shape.3. It is shown that the characteristic length … More included in interfacial stress intensity factors can be considered as the fracture process zone ahead of the crack tip. By using this characteristic length, the generalized fracture criteria can be obtained in any kind of material pairs if the mechanical properties of the interface are same.4. The mixed mode fracture tests for bonding specimen were conducted and the fracture criteria of the bonding interface were obtained. It is shown that the generalized fracture criteria can be applied to the bonding fracture test.5. The new peel test method to measure the interface strength under several kinds of phase angles has been developed. This test method is called as Multi-stages peel test. The peel strength of multi-layer films, that is composed of Si/PI/Cr/Cu, were measured. In conventional method, the thickness of peeled film was influenced to the peel strength. However, by considering the energy balance under the steady-state peeling, the peel strength independent of film thickness can be obtained. Less