Laminated structures made from cord-rubber composites find applications in the automotive and aerospace engineering industries, especially for vibration insulators, air-springs and belt structures. For example, two-ply cord-rubber composite laminates with 2a cord orientations are being used in air-spring/belt construction. Cord-rubber composite structures are subjected to dynamic loading in addition to static axial and bending loading during service. Due to their complex construction, these composites exhibit coupled bending-twisting and extension-twisting behavior. While two-dimensional (2-D) studies may provide some insight into the quantitative aspects of vibration modes and give preliminary information, they do not yield qualitatively useful results for failure problems. To understand and predict dynamic failure modes, it is essential to model accurately their truly three-dimensional (3-D) dynamic response. Such an accurate and realistic simulation can be achieved only through the use of three-dimensional dynamic analysis.
There are a number of free vibration studies of rigid matrix composite structures in the literature. However, there are only a limited number of free vibration studies on laminated cord-rubber composite structures. Since cord-rubber composites are very different from rigid matrix composites in terms of degree of anisotropy, such as large deformation of the rubber material, twisted nature of the cords, etc., there is a need to develop computational models to understand better the delamination type failures and to develop more effective, durable composite structures under dynamic loading.
Recently, we have presented a three-dimensional finite element model to study the static behavior of two-ply laminated cord-rubber composite structures [1]. In this study, three-dimensional linear finite element computations are performed to investigate the free vibration response of two-ply cord-rubber composite structures with 2a cord orientations. The results of natural frequencies and mode shapes from the three-dimensional finite element analysis are presented. Parametric studies were performed to examine the effects of cord orientation, anisotropy, boundary conditions and interply thickness on natural frequencies and mode shapes.