Study on the extension of feasible design region and optimum for effective engineering elastic moduli of composite laminate by using continuous variables

Abstract

In this paper, the feasible region of design variables is extended by using continuous variables, and an optimization method to find the optimum satisfying various design requirements on in-plane and bending effective engineering moduli is proposed with the genetic algorithm (GA). In the optimal design of effective engineering moduli, we treat the layer orientation angle as the continuous variables, not as the discrete variables such as 0°, ±45° and 90°, and extend the feasible solution region to find the better optimal solutions than those in the case of the limited design variable region. Then, the feasible design region is extended to 1.23•1027, 1.41•1024 times in comparison with the case of the discrete variables such as {0°, ±45°, 90°}and {0°, ±30°, ±45°, ±60°, 90°}, and the optimum that satisfies the severer design requirement and whose effective engineering moduli increase by about 4.47% of those of the discrete variables can be found. And the methods of various maximum moduli design and the criterion moduli design for requirements on in-plane and bending effective engineering moduli that arise from application are proposed. In order to solve these optimization problems we selected the reasonable genetic operators of GA to increase the global property and convergence of solutions.The GA operation with the proposed genetic operators increases the variety of individual population to rise about 2.7 times the convergence rate, and to rise the average fitness of the optimum by 6.7%. The effectiveness of the proposed method is demonstrated by the numerical examples.