Robust Design of a Flexible Structure Reinforced by FRP Sheets

Abstract

This paper presents a robust method for designing a flexible structure reinforced by fiber-reinforced plastic (FRP) sheets. An FRP sheet has a high ratio of strength to weight and is widely used to reinforce various structures. Vibration characteristics of a structure reinforced by FRP sheets can be easily modified by changing design variables such as the relative volumes of fibers and matrix, the fiber angle and the number of layers. Therefore small variation of the design variables gives rise to drastic change in the vibration characteristics. The focus of this paper is on variation of the modulus of longitudinal elasticity of a structure reinforced by FRP sheets. We propose a constraint that takes into account the variation band of the elasticity of the structure and specifies the total variation of natural frequencies of low-order modes. To maximize the natural frequencies, the design variables are determined by using an optimization technique with this constraint. The validity of the present method is verified by numerical examples and by comparison with results of experiments.