Quasi-periodic excitation in a delaminated composite beam

In this paper the effect of quasi-periodic excitation was investigated on the dynamic stability of a delaminated composite beam. The quasi-periodic excitation was obtained by combining a longitudinal harmonic excitation with a random like transverse, in which case the simplest approximation is the desired one. The mechanical model of the structure was created using the Euler-Bernoulli beam theory combined with possibility of axial deformation. The beam was discretized using the finite element method and stability charts for the global structure were determined using the largest Lyapunov characteristic exponent. The amplitude and frequency of the time dependent longitudinal force and displacement excitation, the length of the delaminated part and the amplitude of the beam end corresponding to the first mode shape were examined on the dynamic stability regions of the constrained mode model. The results were compared with the case when there is no transverse excitation using Bolotin's harmonic balance method. It was found that in case of small beam end amplitudes the results of the two methods is in good accordance.