Author(s)

P. Prochazka & S. Peskova

Abstract

The process of debonding of fibers from a matrix in composite materials plays a very important role in the assessment of the bearing capacity of the aggregate. A couple of papers by the present authors have focused on this problem. Here the problem of debonding will be concentrated on a process being brought about due to a normal load applied to a unit cell in a periodic medium. Such an approach is atypical in the general problem describing the mechanical behavior of the interface between fibers and matrix in composite materials. The standard procedure consisting of both normal and shear influences is more complicated due to the strongly non-linear behavior of the formulation. Plenty of models have been proposed in the past. Some of them are very usable, but suffer from inaccurate formulations, numerical instability or are too robust. In this paper a new approach is suggested. It consists of introducing eigenparameters in the interfacial zone describing the neighborhood of fibers. Considering a matrix and also the fibers as stiff enough, the damage will occur only in the interfacial zone. Because the damage can be described by eigenparameters, the influence matrices are created in the sense of generalized transformation field analysis to speed up the iterative solution of the nonlinear problem. It will be shown that this approach offers a new very efficient and fast algorithm, which in our case is based on finite element methods. The generalization to boundary elements seems to be simple. The matrix will obey von Mises – Huber - Hencky ideally elasto-plastic states, while fibers remain elastic. This particular material describes especially steel-epoxy, glass-epoxy, or graphite-epoxy composites. A couple of examples will show the ability of the approach envisaged. Keywords: debonding of fibers in composites, eigenparameters, microcracking, constitutive behavior.

Keywords

debonding of fibers in composites, eigenparameters, microcracking, constitutive behavior.