Optimum design of composites.

摘要

The thesis describes advanced design techniques for composites associated with stress concentrations, buckling and dynamic behaviors. Due to a common presence of geometric discontinuities such as holes and notches and diverse operating environments, the research focuses on optimizing the design of perforated composites to reduce stress concentrations, increase buckling resistance and enhance their dynamic performance when operating in hygrothermal environments. Total Lagrangian nonlinear static, buckling and hygrothermal dynamic FEA formulation procedures for both 3D solid and laminated composite shell elements are newly established and their accuracies verified. Optimum design is achieved here primarily by synergizing finite element analysis (FEA) with a probabilistic evolutionary genetic algorithm (GA). This approach is well suited for enhancing the response of orthotropic and/or laminated composites which involve many design variables.; Recognizing ability of the stiffness in the neighborhood of geometric discontinuities to influence composite performance, fiber directions within both individual finite elements and individual plies are optimized locally utilizing an integrated GA-FEA parallel numerical system. Results demonstrates the current approach is superior to more conventional design techniques such as modifying ply thickness or the stacking sequence of individual rectilinear plies.