A procedure for iterative identification of the design variables characterizing interface delaminations in layered composite materials

Abstract The paper deals with the identification of the delamination in composites on the basis of the information for the displacements from the surfaces of damaged bodies. The identification of the active delamination region on the interface between two layers of given composite material is a non-linear programming problem that consists of minimization of a Kohn-Vogelius type of functional [3] with respect to some set of design variables defined from the parameterizing of the delamination region. In the past, classical non-linear programming techniques, like SQP, have been used for solving this problem. For the given requirements, this delamination region is preliminary unknown in shape, dimensions and position. Going back from this well-posed problem, for the Euler-Lagrange equations obtained from a new formulation of the Kohn-Vogelius functional we derive here a direct method for the solution of the inverse problem of delamination. It leads to a computational reconstruction method for finding interlaminar cavities from the measurement of the surface displacements.