On the Use of Shell Theory for Determining Stresses in Composite Cylinders

Abstract

Applying Vlasov-Ambartsumyan shell theory to anisotropic and laminated cylinders, equations are developed for calculating the stresses in a composite tube under combined axial load, torsion, and internal pressure. Comparison to results obtained from exact elasticity theory shows that the shell equations are capable of predicting, with a reasonable degree of accuracy, the large stress gradients found in highly anisotropic tubes. Thus the shell theory provides the experimentalist with a set of closed form expressions for readily defining the proper specimen dimensions for precise characterization of unidirectional and laminated composite tubes. A modification to the shell theory, in which the effects of transverse normal strain are included is also discussed. Numerical results show that such a modification is necessary for determining stresses induced by free thermal expansion. It is also shown that certain classical thin shell kinematic relations are incapable of predicting stresses in composite tubes.