Free Vibration of Variable Angle Tow-Steered Composite Laminates with Bimodulus Materials

A study on free vibration characteristics of bimodular composite materials using shear flexible plate model is presented in this paper. Curvilinear fibers which result in variable stiffness due to change in fiber path angle is considered in this analysis. The material considered exhibits different properties in tension and compression depending on fiber direction strain. The governing equations are obtained by Hamilton’s principle and are solved using finite element approach in conjunction with eigenvalue approach. Natural frequencies are obtained considering both positive and negative half response cycles of vibration. As laminate neutral planes are not known in advance, their positions are found iteratively by assuming mode shape of interest and subsequently applying Newton-Raphson scheme. A detailed investigation is conducted to obtain variation of the fundamental frequency due to change in aspect/thickness ratio, material ratio, plate edge conditions, fiber path angle, layup, etc.,