Abstract: The spontaneous mierobuckling of unidirectional fibre reinforced composites subjected to longitudinal compression is examined in the present paper. The problem is approachel from the elastoplastic microbuckling viewpoint, which leads to a formula on the critical instability load for periodically assembled layered composites. Further determination of the elasto-plastic instability point is facilitated by the compressional stress strain relation, which then gives rise of the final formula of the compressive strength. Our theoretical predictions quantitatively agree with the experimental data of four representative fibre reinforced composites. Qualitative explanations for different compressional kink are band failure modes associated with brittle and ductile fibre reinforcements are given by means of the present theory.

Key words: fibre reinforced composites, elastoplastic microbuckling, compressional strength