Optimal laminated composite shells for buckling and vibration

Abstract

Methods are proposed for the determination of the optimal ply angle variation through the thickness of symmetric angle-ply shells of uniform thickness. These methods use continuous piecewise-linear segment approximations or discontinuous piecewise-constant segment-approximations to the ply angle function. A mathematical programming (MP) problem is formulated using segment ply angles and thicknesses as design variables. A special MP algorithm, capable of treating multiple objective functions, combined with a critical mode search is Used to solve this problem. The procedure is applied to the maximization of the minimum natural frequency or buckling load of a thin, simply supported, circular, cylindrical, angle-ply shell. Results show large performance gains result from the use of optimal variable ply angle configurations, compared to an optimal constant ply angle. The continuously variable ply angle approximation is particularly effective.