STRUCTURE EFFECT AND MICROBUCKLING

At the present time, it is clearly established that the compressive fa ilure in the direction of fibers of a unidirectional ply is not intrin sic to the material bur depends on the structure (stacking sequence, t hickness of the ply and loading). This dependence can be explained by the appearance of fiber microbuckling. The purpose of this work is the 'exact' calculation of the microbuckling modes which may appear in th e laminate. Unlike the local models from the literature, the complete microstructure of a laminate is represented and the modes are sought i n the form of harmonics in the direction of fibers. The following para metric study clearly shows the effect of the ply thickness, the bounda ry conditions, the loading, the stacking sequence and the presence of damage, on the mode and on the critical strain of microbuckling. Moreo ver, these results lead to a very reliable homogenized model which giv es the possibility of-taking into account the effect of fiber alignmen t defects and the appearance of plasticity inside the matrix. (C) 1996 Elsevier Science Limited