Reliability-based Robust Design Of Laminated Composite Structures

The use of composite materials in aerospace structures has been increased rapidly due to their great specific stiffness, low weight, and outstanding designability characteristic. In the practical application, we can change the fiber direction and the thickness of the composite laminates to meet the requirements of the mechanical properties. The fiber reinforced composite laminates are very sensitive to the thickness of the layer, the changes of the environmental load and the layer angle. In order to ensure the safety of the structure, the optimization of the structures reliability is used to optimize the size of the composite structures, It is the main research and discussion in recent years that use the reliability of the structure as the limiting condition to optimize the structure of composite materials. For the reliability-based design optimization of composite structures, by changing the angle of single layer, the thickness of single layer and other parameters to obtain the optimum structure, but the structures parameters of the composite structure will produce an error in the process of production, which will influence the reliability of the composite structure. In order to make the structure insensitive to the fluctuation of the structural parameters, we can use the robust optimization method to design the composite structure. Robust design make the design of structure insensitive to the fluctuation of the structure size and external load. Due to this kind of design method considering the structural reliability may be influenced when it is practical manufactured and practical used. Robust design can improve the quality of the products. So people pay more attention to robust design.This paper addresses the problem of structural optimization and robust design of laminated composite materials with reliability constraint using a genetic algorithm. First of all, this paper based on the reliability of the laminated composite structures to optimize design. Using the classical laminate theory to calculate the mechanical properties of laminated composite structures. The failure of composite materials based on the hypothesis of the first layer failure and Tsai-Wu criterion. In this paper, the structure strength parameters and load are random variables, the reliability analysis is performed using Monte Carlo and using the genetic algorithm to optimize structure to obtain the optimal laminated structure.After finished reliability based optimization of laminated composite structures, A two-stage optimization method was proposed in this paper and this method based on reliability optimization results to proceed robust design of laminated structure. Under the structural reliability and the overall thickness as constraints to obtain the optimal structure of minimum structural sensitivity. Traditional structural robust design is a kind of multi-objective optimization problem, traditional robust design usually use the weighting factor method. But this method solve the problem of robust design of laminated composite structures has a lot of deficiencies. An approach that simultaneously considers objective function and robustness is proposed in this paper. This method under the condition of give up a certain thickness to obtain the great robustness of composite laminated structure. This method greatly simplifies the robust design problem. The method make a double target optimization design problem into two single objective optimization problems. This method can provide an effective reference approach for practical applications. We analyzed the different optimized results under different restricted conditions and provided a reference for practical applications. This optimization method can greatly reduced the difficulty of structural robust design and solve some complicated practical problems.