Using Modal Analysis for Estimation of Anisotropic Material Constants

A dynamic method is presented for the estimation of the in-plane elastic properties of structural panels modeled as thin orthotropic plates. The method utilizes the concept of modal analysis. Results from experimental modal testing are matched with theoretical modal analysis calculations for a set of plate bending modes and one in-plane mode of the compression type. The elastic constants E1, E2, and G12 are estimated by minimizing the relative errors between corresponding experimentally and theoretically determined eigenfrequencies. A ratio of two chosen mode shape values of an in-plane compression mode yields an estimate of the Poisson ratio ν21. The other in-plane Poisson's ratio ν12 is calculated on the basis of E1, E2, and ν21 using Hooke's generalized law. Some redundant information gained from the experimental model testing is used to minimize possible errors in the test and evaluation process. The method is applied to one type of wood panel material, namely oriented strand board.