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Unformatted text preview: New Families of Hygrothermally Stable Composite Laminates with Optimal Extension-Twist Coupling Robert A. Haynes ∗ Georgia Institute of Technology, Atlanta, Georgia 30332 and Erian A. Armanios † University of Texas at Arlington, Arlington, Texas 76019 DOI: 10.2514/1.J050596 The necessary and suf fi cient conditions for hygrothermal stability of laminated composites are presented. A thorough survey of hygrothermally stable families is performed to identify stacking sequences that produce maximum extension-twist coupling. This is achieved through a constrained optimization routine, where the objective functionis derived from theconstitutive law givenin classical lamination theoryand the constraintsare thenecessary conditions for hygrothermal stability. A representative sample of these optimized laminates are constructed and tested to demonstrate signi fi cant improvement in coupling over the previously known optima. Comparisons are made with a nonlinear model and fi nite element analysis. An investigation of the robustness of the optimal stacking sequences to errors in ply angle typical of hand-layup manufacturing is presented. Nomenclature A ij = in-plane stiffness coef fi cients B ij = coupling stiffness coef fi cients b i = coef fi cients that are functions of A ij , B ij , D ij , and geometric parameters D ij =...
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- Spring '11