Optimization of composite drive shafts against whirling instability

Abstract

This paper presents a model for maximizing the critical speed of a composite drive shaft without the penalty of increasing the total structural mass. Additional constraints include stress, torsional buckling as well as side constraints. The selected design variables are the fiber volume fraction distribution, fiber orientation angle and wall thickness of the shaft. Both continuous and discrete grading patterns have been implemented in the directions through the shaft wall thickness and length. Various power-law mathematical expressions describing material grading have been utilized, where the power exponent was taken as a main design variable. The associated optimization problem have been formulated as nonlinear mathematical programming problem and solved by applying the MATLAB optimization ToolBox routines, which implement the sequential quadratic programming method. A case study including the design optimization of a pinned-pinned slender shaft made of carbon-AS4/epoxy-3501-6 composites is presented. Results have shown that the approach implemented in this study is reasonably efficient to attain improved designs in a reasonable computer time.