Experimental And Numerical Analysis Of Some Interfacial Mechanics Problems In Dissimilar Materials

With the development of science and technology, more and more new materials used in engineering structures are replacing to traditional materials gradually, such as fiber reinforced composites, sandwich core materials and thin film/substrate functional materials. These materials which contain the different materials are called dissimilar materials. Due to complex physical and mechanical properties of cohesive layer, some complex mechanics problems need to be studied. Shear failure is commonly observed at bonding interface in the dissimilar materials, the shear stress transfer of bonding interface in the dissimilar materials should be studied in detail. Moreover, the dissimilarity of stress singularity at the bonding edges and interface cracks often cause the fracture near the interface edges and interface crack tip. Traditional analysis of materials mechanical behaviors and evaluation methods are not suitable to the bimaterial. If new fracture criterion has to be rebuilt according to the characteristics of interface, these interface mechanical problems must be investigated intensively.Under consideration with above problems on bonding interface, the following works are developed in our research. (1) Phase-shifting digital photoelasticity method is applied to measure the interfacial shear stress of Aluminum alloy/epoxy adhesive joint to investigate the stress transfer at the bond interface, the numerical calculation is used to validate the experimental results. (2) Based on singularity stress field equations of bimaterial joint at the interface corner, phase-shifting digital photoelasticity method is applied to calculate the stress intensity factors, and the numerical calculation is used to validate the experimental results. (3) Based on multi-parameter stress field equations, a nonlinear least-squares method is applied to determine the parameters in the stress field equations of interfacial crack tip by fitting the isochromatic phase-field obtained by phase-shifting digital photoelasticity. The parameters in the stress field equations are determined and automatically by using the nonlinear least-squares method. Simulation and experimental results for the mixed-mode crack tip validate the correctness of the method. Moreover, a systematic error analysis is developed to obtain the better experimental data.