Mechanisms generating residual stresses and distortion during manufacture of polymer–matrix composite structures

The mechanisms causing residual stresses and distortions are considered, and the way they develop during the cure discussed. Experimental results are presented through the cure cycle on curvature of unsymmetric laminates, spring-in of curved sections and stresses in flat plates due to tool–part interaction. It is shown that thermal stresses after vitrification are the main cause of distortion of unsymmetric plates, whereas thermal stresses and chemical shrinkage, while the material is in the rubbery state, both contribute to spring-in. Large stresses can develop due to tool–part interaction, even before gelation.