ON RESIDUAL-STRESS INDUCED DISTORTIONS DURING FABRICATION OF COMPOSITE SHELLS

Channel or angle components are important structural members. It has b een observed that during the manufacture of these components, residual stresses build up. The state of residual stress in these components l eads to a reduction in the enclosed angle where the out-of-plane contr action is higher than the in-plane contraction. This phenomenon (of th e reduction in the enclosed angle) is referred to as spring-in. The re sidual stresses, in addition, may lead to defects such as micro-cracki ng, delamination, etc. The degree of spring-in and the residual stress es may be estimated by analysing the curved portions of these structur al components as sectors of circular cylindrical tubes (see Figure 1). In this paper, a simple mechanics-based model is developed using modi fied shell theory that predicts the degree of spring-in and determines the stresses and strains in cylindrical segments with arbitrary lay-u ps subjected to random temperature gradients. The model accounts for t he resin shrinkage occurring during curing and also includes the effec t of moisture gradients. The accuracy of the present analysis is inves tigated by comparing predicted results with previously published resul ts.