A structural approach of plastic microbuckling in long fibre composites: comparison with theoretical and experimental results

The aim of this paper is to compare some predictions obtained from a structural plastic microbuckling model presented in detail by Drapier et al. (1999), with theoretical and experimental results from the literature. After a short presentation of this model, it is established that with our approach it is possible to find the elastic modes determined by Drapier et al, (1996) on the composite microstructure. The plastic instability mechanism is then investigated and its understanding is refined. Some simulations are carried out varying the fibre initial imperfection, and the results are detailed and compared with predictions from a kink-band model (Budiansky and Fleck, 1993). Compared to the present knowledge, the understanding of the influence of the imperfection shape and of its distribution across the ply thickness is improved and new results are exposed. Validation of the present approach is completed by comparing the influence of both matrix and fibre behaviours as predicted by Budiansky and Fleck (1993) with the ones obtained from our numerical tool, Results demonstrate the influence of the change in the matrix tangent stiffness. Secondly, we have quantified the effects of the applied loading, thickness and stacking sequence on the compressive strength of laminates. Numerical predictions provide new results that yield a proper justification of the very high compressive strength measured with bending tests, These predictions also fit well experimental measurements from the literature showing the effects of the thickness (Wisnom, 1993) and of the stacking sequence (Grandsire-Vincon, 1993) on the compressive strength. For the first time, the effect of the gradient of loading across the laminate thickness is predicted, Results are shown to correlate will with experimental results from Wisnom et al. (1997). (C) 2001 Elsevier Science Ltd. All rights reserved.