Flexural-torsional coupling effect on vibrational characteristics of angle-ply laminates

A mainly experimental investigation is presented on the vibrational characteristics of angle-ply laminate made of carbon/epoxy composite material, considering the effect of flexural-torsional coupling stiffness. This consists of a resonance test on a cantilevered laminated plate model by using laser holographic interferometry. An exact comparison of the coupling effect was achieved by employing two special types of angle-ply laminates, each consisting of eight plies in which one type had the least possible, and the other type, no coupling stiffness at all. The observed results show that the effect of flexural-torsional coupling stiffness on the resonance frequencies is only marginal. By contrast, the vibrational mode shapes are found to be affected considerably by the coupling stiffness. Moreover, the amount of this coupling effect is also observed to depend both on the fiber orientation and the aspect ratio of the plate model. An analytical study was also conducted by using the Ritz energy method and a good agreement between the experimental and the theoretical values is observed upon comparison. (C) 1998 Academic Press Limited.