Wavelet Spectral Finite Elements for Wave Propagation in Composite Plates

The principal objectives of the research are to develop and experimentally validate a predictive modeling capability for simulation of wave propagation in 2-D composite plates. During this reporting period, the Wavelet Spectral Finite Element (WSFE) model for composite plates (developed by Prof. Gopalakrishnan at IISc Bangalore) was implemented at Clarkson. Composite plates were fabricated using aerospace grade carbon fiber prepregs. A scanning laser vibrometer was used to record out-of-plane responses of the plate for Lamb wave actuation. Experimental data and WSFE predictions were shown to have very good correlation for healthy plate. Development of WSFE models for damaged composite plate (transverse crack and delamination) is under progress. Also, the center frequency of tone burst signals is varied to find out its influence on the resulting damage index for a given delamination. It is generally accepted that the wavelength of excitation signal should be less than half the size of damage. However, no further guidance is available in the literature regarding optimal value of excitation frequency for a given damage (delamination) size. The research has resulted in five conference papers so far and three articles are under preparation for journal publication. 1. Summary of Accomplishments (1 April 2010 – 31 March 2011) The two principal objectives of this project are to 1) Develop and validate Wavelet Spectral Finite Element (WSFE) models for composite plates with damages such as transverse crack and delamination, and 2) Perform extensive experimental studies for Lamb wave propagation in composite plates with damages. Use time reversal (and other techniques) to obtain characteristic signals for damages. Determine most suited interrogation mechanisms (i.e., wave type, wave mode) for different damages through both simulations and experiments During this reporting period, the Wavelet Spectral Finite Element (WSFE) model for composite plates (developed by Prof. Gopalakrishnan at IISc Bangalore) was implemented at Clarkson. Composite plates were fabricated using aerospace grade carbon fiber prepregs. A scanning laser vibrometer was used to record out-of-plane responses of the plate for Lamb wave actuation. Experimental data and WSFE predictions were shown to have very good correlation for healthy plate as shown in Fig. 1. Fig. 1. Comparison of velocity response from WSFE and experiments at two sensor locations