Equivalent Single Layer, Zig-Zag, and Layer Wise Theories for Variable Angle Tow Composites Based on the Generalized Unified Formulation

摘要

Variable Angle Tow (VAT) composites remove the constraint of having straight fibers, typical of traditional composite structures. This dramatically increases the design space and allows a more effective tailoring of the material properties to minimize the weight and increase structural performance. Equivalent Single Layer, Zig-Zag, and Layer Wise theories with different orders of expansions for the different variables are obtained with the Generalized Unified Formulation (GUF) for the analysis of VAT structures. The finite element discretization is performed with a fourth-order triangular shell element presenting 15 nodes. The interlaminar displacement continuity is imposed with the finite element assembling in the thickness direction of the layer stiffness matrices, whereas the inter-element displacement compatibility is enforced with the penalty method. This approach allows one to use independent GUF discretization for any desired direction within each element, providing great versatility (accuracy vs computational time) in the structural modeling. A transverse stress recovery procedure based on the integration of the equilibrium equations and taking into account the variability of the structural properties due to the fibers' curvilinear paths is also presented. Results are compared with the literature and a commercial software (NX NASTRAN) featuring 3D finite elements.