Modelling of interfacial fracture

This paper adresses the problem of modelling the complex non-linear phenomena of indentation and fracture of brittle materials. These include frictional contact interaction, crack propagation and debonding of laminated brittle three-dimensional finite bodies. An original unified methodology for the solution of the related boundary value problems, based on combination of the variational and boundary integral multi-region approaches, has been developed. The discretization of the involved surfaces and unknown functions leads to a finite dimensional quadratic programming problem, solved by a modification of the gradient-projection method. The discretized version of the algorithm has been implemented in the form of computer codes for both conventional serial and parallel Connection Machines CM2/5, multi-processor SGI Challenge Series. The model components were tested against analytical and numerical results. Crack propagation and debonding of the interfacial boundaries in a quasi-static scenario were investigated. The model has been used for numerical simulation of the Micro-Scratch Test to aid in the development of procedures to evaluate adhesion for coatings. The model demonstrated that for the Micro-Scratch Test (using the Knoop indenter) the dominant mechanism of the interfacial debonding is different than in indentation fracture of the homogeneous materials. Numerous experiments with the microscratch technique show that this test, with the aid of numerical model, can quantify a coating/substrate interfacial strength and characterize the factors influencing it.