Designing of interlayers between materials with minimum stress level at the interface

Abstract The stress concentration at the interface between two dissimilar materials is a serious problem in designing adhesive joints and composite structures. Numerous studies have been conducted with the aim of reducing the stress concentration at the interface between dissimilar materials. In most of these works it was achieved by changing the geometry or properties of one of the materials at the edges of the interface. In this paper we propose a method of determining the values of elastic constants of the interlayer material and its geometry near the edges of the interfaces, to reduce the stress concentration. The method is based on the results of solving the problem of stress optimisation in the vicinity of singular points, according to which the optimal variants determine the boundary between the solutions with and without stress singularity. The paper presents the results of the construction of eigensolutions in the vicinity of singular points, which allow us to determine the ranges of parameters responsible for the appearance of solutions with and without stress singularity. The main advantage of the proposed method is the possibility of finding the range of optimal configurations for the interlayer, which is made of homogeneous or functionally graded material and used to bond materials having similar or dissimilar properties. A number of model problems are solved to demonstrate the capabilities of the proposed method in a search for the optimal mechanical characteristics of the elastic interlayer between two similar or dissimilar materials and its geometric parameters, in order to minimise the stress concentration at their interface.