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Fixed Stiffness Weight and Cost Tradeoff of Hybrid Sandwich Structures



Producing a light structure with relatively affordable cost has always been a challenging task for designers. Using a hybrid material approach provides an expanded methodology to combine materials having different costs and properties (for example, combining fibers with high cost and high stiffness fibers such as carbon with low cost, less stiffness such as glass). Hence, a comparative approach is required for the evaluation of design solutions in terms of weight and cost. In this study, a methodology for a combined weight and cost optimization for sandwich plate with hybrid composite facesheets and foam core is presented. The weight and cost of the sandwich plate considered are the objective functions with respect to the equivalent constraint based on the bending stiffness of the sandwich plate. The sandwich plate considered consisted of thin hybrid composite facesheets, symmetric with respect to the mid-plane of the sandwich plate. The facesheets considered consisted of longitudinal carbon and glass fiber reinforced polymer. Two different densities (with two difference cost) of polyisocyanurate closed-cell foam core were studied. Singleobjective and multi-objective optimization techniques were performed to obtain the optimum weight and optimum cost of the sandwich plate. An Interior-Point Algorithm was used to perform the single and multi-objective optimization. For the multiobjective cases, a weighting method was used to solve the problem by combining the objective functions of weight and the cost into one objective and Pareto trade-off curves were constructed. The weight of the adhesive bond material was neglected and only the cost of the fibers and the core materials was considered in this study. A key finding is that design curves can be created showing that hybrid solutions can be preferred when both cost and weight are considered simultaneously.

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