WIT Press

Debonding Process In Composites Using BEM


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P. Prochazka & M. Valek


The paper deals with the debonding fiber-matrix process in composite materials. A couple of papers has been focused on this problem by the authors of this paper. As usual, the influence of separate pure normal and pure shear energy has been studied for obtaining the overall material properties. Such an approach is a simplification of the problem describing the mechanical behavior of the interface between fibres and the matrix in composite materials, since the standard procedure consisting of the superposition of both normal and shear influences is no longer admissible due to the strongly nonlinear behavior of the process. In this paper a more complex development of the debonding zones is shown, namely, responses of successively applied normal and then shear load and also first shear load and then normal load are observed. The physical behaviour of the interface is non-convex. This assertion immediately follows from the penalty formulation of the problem as published recently by the first author. The penetration of fiber into the matrix is not allowed in every case. In this contribution we start with a definition of the model describing the transfer of elastic stresses from the matrix to the fiber. Then, the contact problem is formulated in a manner leading to a very fast Uzawa’s algorithm for its solution. In order to speed up the iterative solution influence matrices are created before the iteration. The approach turns to a similar one known as generalized transformation field analysis. Debonding processes in the interfacial zone are illustrated by examples. Keywords: composites, debonding process, general transformation field method, Uzawa’s algorithm. 1 Introduction A 2D unit cell model with diagonal symmetry is considered to study an effect of imperfectly bonded interfaces. This simplification has only formal nature, and is


composites, debonding process, general transformation field method, Uzawa’s algorithm