Identification of delamination defects through covariance of energy change: numerical modeling

Delamination is currently a difficult detectable form of damage in composite laminate materials. This paper presents a method to more easily detect delamination damage within composite materials using finite element analysis modeling, through the covariance of energy change. Lamb waves were introduced and recorded through an actuator and sensors made of piezoelectric material. The data were then analyzed through the fast Fourier transform (FFT). Using the data from the FFT, the idea of covariance of energy change was suggested to correlate with defect characteristics. By comparing the covariance of energy change in beams with different delamination sizes, thicknesses, and depths, correlations between the covariance of energy loss and defect characteristics were able to be developed. With these correlations, the severity of these damages was able to be quantified.