APPROXIMATE FUNDAMENTAL-FREQUENCY OF VARIABLE THICKNESS COMPOSITE PLATES

An approximate closed-form expression is presented which can be used t o compute the fundamental frequency of symmetric rectangular composite laminates of variable thickness. The desired expression is developed using the method of eigensensitivity analysis. Results are presented f or a parabolic thickness variation in one direction, with the taper pa rameter beta varying from 0.5 to 1.5, various plate aspect ratio R and a high material stiffness ratio E-11/E-22 using both simply supported and clamped boundary conditions. Comparison of the predicted fundamen tal frequencies with those numerically computed, using the Rayleigh-Ri tz method, demonstrates the utility and accuracy of the expression. (C ) 1997 Published by Elsevier Science Ltd.