OPTIMAL FIBER ORIENTATION OF ANTISYMMETRIC HYBRID LAMINATES FOR MAXIMUM FUNDAMENTAL-FREQUENCY AND FREQUENCY SEPARATION

Optimal fibre orientations of antisymmetric, angle-ply laminates are determined with the objective of maximizing their vibration characteristics. The design problems involve the maximization of the fundamental frequency and the frequency separations subject to a mass constraint. The laminated plate is constructed as a sandwich hybrid structure with outer layers of a high-stiffness material and inner layers of a low-stiffness material. The numerical results are given for laminates made of a boron/glass material combination. Cost and frequency implications of hybrid construction are discussed. Comparative studies of hybrid and non-hybrid optimal laminates of equal mass are presented in graphical form. The optimal fibre orientations are found to display several jump discontinuities when plotted against the aspect ratio. It is observed that the results for hybrid laminates do not always fall in between those for non-hybrid laminates. Furthermore, the vibration characteristics of optimal hybrid laminates are found to be better than those of non-hybrid ones of high-stiffness material for certain ranges of problem parameters. © 1991.