An analytical and numerical study of fiber microbuckling

In this paper a new analytical model which accounts for both shear and normal interfacial stresses as a function of fiber volume fraction and microbuckling wavelength is developed to analyze the compressive behavior of unidirectional fiber-reinforced polymer composites (FRP). In this model the relationships between the compressive strength, interfacial stresses, microbuckling wavelength and fiber volume fraction are studied. Contrary to the commonly accepted idea of the occurence of an extension mode of microbuckling, it is found that the shear mode is always the preferred buckling mode rather than extension, except for the case of very low fiber volume fraction composites in which case the fibers perform individually as in a single fiber case with no interaction in between them. In addition to the analytical study, a finite element analysis is carried out to investigate the in-plane microbuckling behavior of unidirectional composites. The results of the finite element analysis are found to be in close agreement with the results of the analytical model.