Design Optimization of Composite Plates: Part II—Structural Optimization by Plydrop Tapering

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Abstract
A preliminary design tool was developed to optimize structures such as beams and plates, with optional cutouts, subject to multiple loadsets and any boundary conditions. SUNSPOT provides with simple, tapered and manufacturable layups. Sublaminates, made of multiple plies at various orientations, combining one or more materials, are repeated or dropped in different zones of the structure, yielding the plydrops taper while ensuring physical continuity of the fibers in all composite layers. The orientation and thickness of each ply group in this reference sublaminate as well as its number of repetitions in the zones across the structure, are optimized using the Nelder-Mead algorithm in conjunction with parametric SAMCEF Finite Element Analyses, all integrated within SUNSPOT. The optimization objective is minimum weight for first ply failure strength. Maximum displacement constraints and economical manufacturing can be enforced additionally. Therefore, extended Tsai-Wu strength failure criteria were derived; new stiffness control criteria and a manufacturing complexity index were developed [1,2].