RIA: Experimental Simulation of Crack Initiation at Bimaterial Interfaces due to Mechanical and Thermal Loads

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Experimental research, dealing with quasi-static and dynamic crack initiation and growth at material interfaces subjected to mechanical and thermal loading, will be carried out. The research will contribute to a better understanding of interfacial failure mechanisms which predominantly control the fracture behavior of multi-phase materials such as polymer and metal matrix composites, metal filled composites, and of adhesive bonds and thin films on substrates. The proposed work is concerned with crack initiation and growth simulations under controlled loading conditions in bimaterial specimens. Interfacial crack tip deformations will be optically measured prior to and at fracture initiation. A newly developed, real time, full field optical technique, 'Coherent Gradient Sensing' (CGS), will be utilized as an experimental tool for measuring deformations near interfacial cracks. From these high resolution optical measurements, local crack tip parameters such as complex stress intensity factor and crack tip mode mixity will be inferred. The optical measurements will allow us to seek relationships between the local crack tip parameters and external/material parameters such as remote loading and material property mismatch. This will provide valuable data for identifying parameters which significantly influence crack initiation at interfaces and for establishing interfacial failure criteria.