Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information The principal goal of this research is to advance the technology of structural health management (SHM) for composite structures. Wave propagation based methods have shown promise for SHM of composite structures. The spectral finite elements (SFE) method is highly suitable for wave propagation analysis due to its frequency domain approach which yields models that are many orders smaller than conventional FEM. Wavelet spectral finite element (WSFE) method overcomes the "wrap around" problem to accurately model 2-D plate structures of finite dimensions. The specific accomplishments of the research are: developed WSFE model for damaged composite plate with transverse crack; validated WSFE modeling of Lamb wave propagation in healthy composite plates through experimental measurements; implemented 'baseline-free' Damage Force Indicator method for delamination detection using dynamic stiffness matrix from WSFE model of healthy plate; developed Modified Time Reversal method for Lamb wave based 'baseline-free' damage diagnostics; and investigated effect of tone burst center frequency on instantaneous phase based delamination detection.structural health management, wavelet spectral finite element, composite structures, damage detection U U U
UU 16Ratneshwar Jha (315) 268-7686