Thin-walled thermoplastic composite structures, with near-continuous fiber lengths in random orientation, are becoming more popular due to material cost and mass savings, especially in the automotive industry. Considering this thin-walled structure as a thin beam, its dynamic characteristics are similar to those of a vibrating transverse beam. The near instantaneous removal of a known deflection causes the specimen to vibrate. Acceleration data is collected at different points across the specimen. Statistically adequate auto-regressive models are fit to the data and decomposed. The resulting frequencies are applied to the Rayleigh quotient obtained from the one-dimensional wave model. After first evaluating a beam of known uniform properties, a composite plaque is evaluated. The frequencies are then applied to the model with known boundary and initial conditions. From the frequencies and wave model, the material's moduli at different points on the plaque are estimated. The result of this research is the correlation of a mathematical model from the dynamic signatures of the structure and its decomposition to the structure's material characteristics.
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