Out-of-plane stresses in composite shell panels: Layerwise and elasticity solutions

Boundary-layer effects in lengthy cross-ply laminated circular cylindrical shell panels under uniform axial extension are investigated by two analytical solutions. First, Reddy's layerwise theory with state-space approach is utilized to determine the local interlaminar stresses. In this method, the general displacement field is discretized through the shell thickness by a linear shape function. When the shell panel is subjected to an axial force, the axial strain is estimated by an equivalent single-layer theory. Second, the stress-function approach along with Fourier series expansion is applied to develop a novel elasticity solution. The elasticity solution, which is based on simply-support edge conditions, is presented to show the effectiveness of the first solution. The numerical results show good agreements. Interlaminar stresses within various symmetric and unsymmetric cross-ply composite shell panels are then calculated and discussed. It is shown that the normal out-of-plane stress can get high magnitudes along the physical interfaces.