Estimation of elastic and modal parameters in composites using vibration analysis

Abstract

This study presents the application of vibration analysis in the determination of elastic constants (i.e. Young’s modulus in fiber direction, transverse Young’s modulus, and shear modulus) and modal damping ratios of a unidirectional composite beam. The frequency domain approach is used for the estimation of material constants, whereas modal damping ratios are predicted by the use of short-time Fourier transform (STFT). An analytical expression of the STFT for the free vibration response of a viscously damped system has been derived using the Hanning window. Analysis of a simulated vibration for a three-degree-of-freedom system has revealed that the STFT is capable of predicting the modal damping ratios accurately even when they are considerably large. For the experimental assessment of modal damping values of a composite beam, longitudinal, flexural, and torsional vibration responses are analyzed by both the STFT and well-known Q-factor approximation, and the obtained results show very good agreement.