An Analytical Method for the Evaluation of Interlaminar Stresses Due to Material Discontinuities

Abstract

Interlaminar stresses arise in regions with in-plane stress gradients. These in-plane gradients could arise due to loading conditions, geometric or material characteristics. One of the material characteristics which could cause such gradients is a sudden transition in material properties occurring at regions of implants within a structure, making them potential delamination sites. Such implants are being used in the design of adaptive structures. The proposed method efficiently evaluates interlaminar stresses at material discontinuities. The laminate is divided into two regions with different layups which are joined together. The stresses in each region are expressed in terms of eigenfunctions which satisfy equilibrium. The principle of minimum complementary energy is used to obtain the differential equations of the problem and thus solve for the eigenfunctions in each region. The analytical form of the stresses enables easy application of averaging type criteria to predict delamination initiation.