THE OPTIMAL DESIGN OF STRUCTURE OF GRP/COMPOSITE BIADES

GRP/composite have been widely used in various types of blades. This paper presents a optimal design of GRP/composite blades with constraint conditions of stress and lower limite on fundamental frequency. The shape of Blades cross section is hollow thin wall structure filled with foams.The laminates consist of the unidirectional layer and a surface layer.Both layers lay up along the blade axis. The design variables are thickness of the unidirectional layer. The thickness of the surface layer is specified by technologic and structural demands. Tne constraint conditions of lower limite and tapered thickness are also considered. The optimization is obtained by combining the optimality criterion and mathematical programming. The stress constraint is dealed with by using the full stress criterion. The frequency constraint is dealed with by using kuhu-tucker condition and weight-minim um operation is given to reduce the weight of blade. The Frequency-modification operation is also used to change the fundamental frequency into specific band. In order to obtain the frequencies, the discrete vibration equations for coupled flapwise bending and chordwise bending of a rotating blade are derived by Galerkin method. Finally two numerical examples are given.It is shown that the computional method is efficient for dynamic structural optimization of GRP/composite blades.