Stresses and Deformations Induced during Manufacturing. Part I: Theoretical Analysis of Composite Cylinders and Shells

Composite cylinders and cylindrical shells are important structural members. It has been observed that during the manufacture of these components, residual stresses build up. In composite cylinders, the state of residual stresses may lead to defects such as micro-cracking, fibre waviness, delamination, and wrinkling, which might degrade the final mechanical performance of the cylinders. In the case of cylindrical segments, the residual stresses also lead to a reduction in the enclosed angle where the out-of-plane contraction is higher than the in-plane contraction. This phenomenon (of the reduction in the enclosed angle) is referred to as spring-in. In this paper, a simple mechanics-based model is developed using modified shell theory that predicts the degree of spring-in in anisotropic cylindrical shells and determines the residual stresses, strains and displacements in both anisotropic laminated composite cylinders and shells with arbitrary lay-ups subjected to random temperature gradients. The model accounts for the resin shrinkage occurring during curing and also includes the effect of moisture gradients. The effects of various factors such as geometry of the component, the ply stacking sequence, the part thickness and the tool radius are examined. The accuracy of the present analysis is investigated by comparing predicted results with previously published results.