Estimation of normal mode and other system parameters of composite laminated plates

To determine the natural frequencies and damping ratios of composite lamina ted plates. we present an efficient modal parameter estimation technique by developing a residual spectrum-based structural system reconstruction and using the system matrix coordinate transformation. The modal parameters can be estimated from poles and residues of the system transfer functions expr essed in modal coordinate basis, derived from the state space system matric es. However. for modal parameter estimation of multi-variable and higher or der structural systems over broad frequency bands, this non-iterative algor ithm gives high accuracy in determining the natural frequencies and damping ratios. It is numerically well behaved unlike iterative frequency-response -function (FRF) curve-fitting methods. From vibration tests on cross-ply an d angle-ply composite laminates, the natural frequencies and damping ratios can be estimated using the modal coordinates of the structural system reco nstructed from the experimental FRFs. These results are compared with those of finite element analysis and single-degree-of-freedom curve fitting. (C) 2001 Published by Elsevier Science Ltd.