An exact solution for improved metal-composite joints reinforced by FG inter-layers

A two-dimensional analytic solution based on linear elasticity theory is used to investigate the effect of using a functionally graded material (FGM) as an inter-layer in reducing the stress concentration in non-axisymmetric loaded metal-composite joints. The geometry of the joint consists of a metal cylinder surrounded in a composite thick plate and loaded arbitrarily by in-plane radial force profile, the condition of which occurs in double-lap pins, bolt joints, and T-bolt joints. The significant difference between the mechanical properties of the adjacent materials induces a stress concentration in the flexible part of the joint. In this work, an analytic solution based on the Airy stress function is used and derived into the strain compatibility equation in two-dimensional problems. The power law model is used for the FGM property variation, and a transversely isotropic model is considered for the composite plate. A two-dimensional condition is assumed for the structure. The results of several models are compared with the finite-element method and show good conformity between the two methods. In some cases, by using the FGM inter-layer, the stress level in the surrounding plate would be decreased significantly