Buckling and Vibration of Unsymmetrically Laminated Cross-Ply Rectangular Plates

An exact solution and numerical results are presented for simply supported plates that are laminated unsymmetrically about their middle surface. The coupling between bending and extension induced by the lamination asymmetry substantially decreases buckling loads and vibration frequencies for common composite materials such as boron/epoxy and graphite/epoxy. For antisymmetric laminates, the effect of the coupling dies out rapidly as the number of layers is increased. For generally unsymmetric laminates, however, the effect of coupling dies out very slowly as the number of layers increases. That is, having a large number of layers is no guarantee that coupling will not seriously degrade buckling resistance and vibration frequencies. Thus, designers must include coupling between bending and extension in all analyses of unsymmetrically laminated plates.