A nondestructive method to determine material properties in orthotropic plates

Abstract An electronic speckle pattern interferometer (ESPI) is used to determine modes of vibration in rectangular, orthotropic, free‐free plates; that is using a noncontact, nondestructive, optical method. It is shown, using the finite element method (FEM), that each of the first three modes of vibration in rectangular orthotropic plates has a strong dependence upon only one of the main material parameters, namely the in‐plane shear modulus and the two Young's moduli, respectively. With this one‐variable dependence it is a simple task to determine the effective material parameters. This method has several obvious advantages compared to the use of test bars and it can be extended to give a measure of the damping parameters and probably also be used for production control. Preliminary results are presented and discussed.