Interface behaviour in laminates with simplified model

This paper focuses on the mechanical definition of the interface in the composite laminates. The chosen point of view is reduced to a multiparticle model vision of the interface (as for the shear-lag analysis). First, we describe several of such multiparticle models, and detail our own proposal, using a Reissner variational principle. We propose then a general expression for the interface behaviour in laminates which involves more than the two close ply stiffnesses and the stresses at the considered interface. By studying the specific case of a [0,90]s, we can compare to over formula found in literature and to a finite element approach. We examine also the stress fields shape, and the stiffness reduction versus crack density, provide by the analysis. We discuss therefore the validity of the classical interface stiffness concept used in a more general framework, for example, for laminates different from the academic [0,90]s.