EFFECT OF SHEAR DEFORMATION ON THE FUNDAMENTALFREQUENCIES OF COMPOSITE LAMINATES IN DIFFERENT THICKNESS

Using of composite materials in the structures has increased dramatically in the past two decades, due to the unique advantages of these materials such as high strength to weight ratio and selection of required material properties in desired directions. The composite materials commonly arecomposed frommultiplelaminates. Preciseknowledgeabout natural frequencies of the laminates is of particular importance for investigating their behavior. Classic theory is often used for analysing composite laminates whih does not onsider shear deformation. In this paper, several plates are modelled in ANSYS program and then frequency and mode shapes are calculated and compared with the exact solution in literature. After model validation, the laminates with different boundary conditions and different thickness are analyzed in ANSYS software and the result of Mindlin theory and classical theory are compared. The results show that for thickness to width ratioless than0.005, the fundamental frequency in Mindlin theory and classical theory are approximately the same.