Improved Method for In-situ Elastic Constants of Isotropic and Orthotropic Composite Materials Using Plate Modal Data With Trimodal and Hexamodal Rayleigh Formulations

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Abstract
This paper relates a further development of an earlier work by the authors, in which they presented a method for deriving the four independent elastic constants (longitudinal and transverse Young’s moduli, in-plane shear modulus and major Poisson’s ratio) of an orthotropic material from resonance data obtained in a modal analysis of a freely-supported plate made out of the material. In the present work, simple averaging, as opposed to the weighted averaging employed in the earlier version, is utilized. The use of three modes and six modes is compared on the basis of results of both the forward and the inverse problems. Results are obtained for materials spanning orthotropy ratios from unity (i.e., isotropic) to about 13. The results suggest that, in comparison with our earlier method, the improved method is easier to use and is just as accurate. The adaptability of the basic method developed by the authors to various levels and types of refinement is also demonstrated, as is the potential of the method for fast characterization of elastic properties of advanced composites.