A 3D delamination modelling technique based on plate and interface theories for laminated structures

In this work a technique for analyzing mixed mode delamination problems in laminated composite plates under general loading conditions is developed. The technique adopts the first-order shear deformable laminated plate theory and the interface methodology, which in turn is based on fracture and contact mechanics. In the thickness direction, an assembly of laminated plate and interfaces models the laminated structure. Delamination may occur along these interfaces, which otherwise perfectly connect the plate models by considering the limit case of interface stiffness coefficients approaching infinity. Lagrange and penalty methods are adopted in order to simulate adhesion and contact effects. Analytical expressions for total energy release rate and its mode components along the delamination front are given in terms of interface variables and of plate stress resultant discontinuities. By means of these expressions the influence of transverse shear on interface fracture analysis is investigated and comparisons with other plate-based delamination models adopted in the literature are established. Numerical results for the energy release rate distributions are given for typical mixed mode delamination problems by implementing the method in a 2D finite element analysis, which utilizes shear deformable plate elements and interface elements. Comparisons with full 3D finite element models show the accuracy and the computational efficiency of the proposed procedure. Some applications are proposed to point out the influence of delamination faces interaction on delamination analysis and the convergence of the mode partition procedure as the delamination front element size decreases, also when oscillatory singularities exist. On the basis of the latter result it transpires that the proposed interface model may represent the physical situation of a very thin adhesive layer.