Imperfection sensitivity of fiber microbuckling in elastic-nonlinear polymer-matrix composites

Imperfection sensitivity of the fiber micro-buckling problem is a fundamental requirement for applying any fiber micro-buckling model for the prediction of composite compression strength. This paper is devoted to prove theoretically that fiber micro-buckling of elastic-nonlinear polymer-matrix composites is an imperfection sensitive problem. From the proof, it follows that compression strength can be predicted by a suitable model that includes fiber misalignment as the imperfection parameter. The conditions on the behavior of the constituents (fiber and matrix) for imperfection sensitivity are derived. A novel representation for the non-linear shear response of the composite is proposed and supported with experimental data. Also, arguments are presented to support the use of composite constitutive equations rather than using micro-mechanics, particularly when material non-linearity is involved. 0 1997 Elsevier Science Ltd.