Buckling and Post-Buckling Behavior of the Delaminated Composite Plates

Multilayer composite materials, having high specific strength and rigidity, are sensitive to interlayer defects. The problem of interlayer laminations in a composite plate subjected to a plane compressive load is studied using a new analytical structure previously developed by the authors. Elastic characteristics of a multilayer package of thin lamination, including the elastic characteristics of separate layers, depending on modulus of elasticity, shear modulus, Poisson’s ratio, and angle of orientation of fibers of the unidirectional layer, are determined. Ratios are obtained for the unidirectional composite material that reflect the contribution of each component (fiber, matrix) in proportion to its volume fraction, according to the so-called “mixture rule”. This work examines the behavior after the loss of stability of an elliptical defect in a composite plate. Only the local bulging of the delamination type defect was considered. The difference between this work and others lies in the fact that the application of the developed method, based on the energy approach, makes it possible to obtain explicit analytical expressions for quantities characterizing the critical load and describing the supercritical behavior of the detached part. The energy method is generalized to the case of analyzing the stability of defects in a non-linear formulation. The value of the critical load was obtained, and the analysis of the supercritical deformation of the defect was made.