Vibration Analysis of Cracked Hybrid Composite Plates using Experimental and Numerical Methods

Light weight composites have been successfully used in many engineering and aerospace applications. Nowadays, hybrid composites are replacing traditional composites because of their inherent advantages like higher strength to weight ratio, reduced cost, and improved resistance towards fatigue and impact loads, higher corrosion resistance etc. Hybrid composites are formed by the inclusion of different varieties of fibers into a specific matrix. The shortcomings of 1 fiber are balanced by the advantages of other, thus providing a perfect balance between economy and performance. Structural defects like cracks are inevitable in composite plates which reduces its strength and stiffness. Since most of the structures fail near their natural frequencies it is important to establish the vibrational behaviour of these structures accurately so as to prevent the phenomenon of resonance. The present study aims to establish above claims by using both experimental and numerical analysis for determining the natural frequencies of hybrid composite plates. The experimental values have been established by Modal Testing using FFT Analyzer. The results have been compared against the values of a Finite Element Package (ANSYS). Various parameters like length, depth, orientation, position of crack, boundary conditions as well number of layers of fibers have been varied to represent a true picture of the influence of local failures on natural frequencies. It has been observed that frequencies decrease with the increase in crack dimensions; increase in number of layers and the values are different for variable positions of crack. The attenuation of frequency is maximum when the crack is at the centre of the plate or when the angle of orientation is 90 degrees with respect to centre of plate. Comparison of experimental and numerical results have been represented in the form of bar charts to provide a better understanding about the dynamic behaviour of composites under the influence of local failures