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

To determine the natural frequencies and damping ratios of composite laminated 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 expressed in modal coordinate basis, derived from the state space system matrices. However, for modal parameter estimation of multi-variable and higher order structural systems over broad frequency bands, this non-iterative algorithm gives high accuracy in determining the natural frequencies and damping ratios. It is numerically well behaved unlike iterative frequency-response-function (FRF) curvefitting methods. From vibration tests on cross-ply and angle-ply composite laminates, the natural frequencies and damping ratios can be estimated using the modal coordinates of the structural system reconstructed from the experimental FRFs. These results are compared with those of finite element analysis and single-degree-of-freedom curve fitting