Free Vibration Analysis of Delaminated Composite Beams

This paper reports the finite element analysis of free vibration of clamped-free and pinned-pinncd symmetric laminated composite beams with different lay-up sequences. Free vibration responses of delaminated beams are examined using Euler-Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB 6.5 software in order to determine the first and second natural frequencies and associated mode shapes of the delaminated composite beams. The constrained mode assumption in delamination vibration is employed. Effects of the delamination width and location, boundary conditions and stacking sequence on the natural frequency and the mode shape of the delaminated beam are investigated. Comparisons with the results in literature verify the validity of the present study. It is found that the width and location of the delamination greatly affect the free vibration of the laminated beam. It is also observed that the second natural frequency value reduces considerably where the delamination is at /1=0.3 or 0.8 for pinned-pinned beam and at /1=0.6 for clamped-free beam.