The cylindrical interface crack in a layered tubular composite of finite thickness under torsion

The present work investigates the problem of a cylindrical interface crack in a bi-layered tubular composite of finite thickness under torsion. Theoretical derivation is performed by the methods of Fourier integral transform and Cauchy singular integral equations. Numerical results of the stress intensity factor are discussed to reveal the coupled effects of the geometrical and physical parameters on the interfacial fracture behavior. The preferred values for the thickness ratio and the stiffness ratio are obtained, which provide necessary reference to the optimal design in engineering. To prevent interfacial fracture, it is better for the two layers to have identical thickness, and under this condition a stiffer inner layer plus a softer outer layer is a preferred choice. However, if the outer layer is enough thin, a softer inner layer plus a stiffer outer layer becomes optimal instead.