Analytical and FEM Solution for Under Layer Shear Stress in Adhesive Lap-Joints in Composites

In this article, the interfacial stresses in single and double lap joints are studied. A quadratic displacement field is assumed in the adhesive layer. For Analyzing stress in joint the free body diagram element of fiber in adhesive and unadhesive part of join has been drawn. By writing the static equation for this elements, the differential equation for joint has been derived. Then by solving this differential equation and using the boundary condition equation, displacement in fibers and so the shear stress in adhesive and axial force in fibers has been derived. The effect of thermal and hygrothermal stresses are also included. It is observed that the peak shear stress developed within the adhesive layer is function of mechanical and physical parameters as Young’s module, Poisson’s ratio, thickness, thermal and hygrothermal coefficients of expansion. The results show that the double lap joint appears to reduce the peak shear stress within the joint significantly. For example maximum shear stress in double lap joints are nearly the half of single lap joints. The results are validated by FEM solution. An excellent agreement is observed between analytical and FE methods.