Vibration Analysis of Curvilinearly Stiffened Composite Panel Subjected to In-Plane Loads

Abstract

This paper presents an efficient finite element approach to study the prestressed vibration mode results of a curvilinearly stiffened composite panel subjected to various in-plane loads. The present method models the plate and the stiffener separately, which allows the stiffener element nodes to not coincide with the plate shell-element nodes. The stiffness and mass matrices of a stiffener are transformed to those of the plate through the displacement compatibility conditions at the plate–stiffener interface via finite element interpolation. Convergence and validation studies have been conducted to verify the present method in the finite element vibration analysis by using the examples from the existing literature. Prestressed vibration mode results are examined for a stiffened composite panel with arbitrarily shaped composite stiffeners in the presence of the in-plane normal and shear loads. Numerical results show the possible benefits of using curvilinear stiffeners to improve the vibration response by increasing both the fundamental frequency and the buckling load through changing the vibration and buckling mode shapes with a negligible or even no weight penalty. The stiffener depth ratio is found to increase both the fundamental frequency and the buckling load, but only up to a certain value. Any further increase in the stiffener depth ratio causes stiffener buckling before plate buckling, and it leads the free and prestressed vibration mode results to behave as the vibration mode results for a plate with simply supported boundary conditions along the stiffeners.