Fundamental Frequency Optimization of Doubly Curved Aerospace Structural Panels via Variable Stiffness Concept

Abstract

In the present study, the fundamental natural frequencies of curvilinear fiber composite doubly curved panel are optimized. Doubly curved panels are used in various components of the structural frames of the aerospace vehicles. The variable stiffness behavior is obtained by altering the fiber angles continuously according to curvilinear fiber path function in the composite laminates. Structural model is utilized based on the virtual work principle. The aim is to achieve the best fiber paths with maximized fundamental frequencies or in-plane strengths for a composite panels. An eight-layer composite doubly curved panel with two types of boundary conditions are considered as a case study in this research. The boundary conditions include; CCCC, FCFC where C stands for clamped, and F for free edges. Von-Karman kinematic strain relations are used and the first order shear deformation theory (FSDT) is employed to generalize the formulation for the moderately thick doubly curved panel including transverse shear effects. Generalized Differential Quadrature (GDQ) method of solution is employed to solve the governing equations of motion. Numerical results demonstrate the effectiveness fiber angle path and boundary conditions on the natural frequencies of the composite panel. The optimal fiber angle paths of each layer are presented for the above cases in free vibration analysis.