EFFECT OF SHEAR DEFORMATION ON THE FUNDAMENTALFR EQUENCIES OF COMPOSITE LAMINATES IN DIFFERENT THICKNESS

Using of composite materials in the structures has increased dramatically in t he 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 co mmonly arecomposed frommultiplelaminates. Preciseknowledgeabout natural frequencies of the laminates is of particular importance for investigating their b ehavior. Classic theory is often used for analys ing composite laminates whih does not onsider shear deform ation. In this paper, several plates are modelled in ANSYS program and then frequency and mode shapes are calculated and compared with the exact sol ution in literature. After model validation, the laminates wit h different boundary conditions and different th ickness 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 theeory and classical theory are approximately the same.

Keywords:

Composite , Laminate , Fundamental Frequency , Mode Shape