Thermally-induced deformation behavior of unsymmetric laminates

A methodology is presented to predict the displacements, particularly the out-of-plane component, of flat unsymmetric epoxy-matrix composite laminates as they are cooled from their elevated cure temperature. Approximations to the strain fields are used in the expression for the total potential energy and the Rayleigh-Ritz technique is applied. Curvatures of the originally flat laminate as a function of temperature are predicted, as are the shapes of the laminates at room temperature. As geometrically nonlinear effects occur, stability is studied. As such, stability and the existence of multiple solutions, which are interpreted as multiple shapes, are prominent features of the problem. Experimental results are presented which confirm the predictions of the theory regarding the existence of multiple solutions, and the magnitude of the displacements. Results are compared with those of several other investigators, and limited finite element analyses are used to further study the problem. (C) 1998 Elsevier Science Ltd.