A robust technique for estimating visco-elastic stiffnesses of plates using air-coupled ultrasound

A robust technique for estimating visco-elastic stiffnesses of composite plates is presented. Generally, material characterization techniques are based on simplified models which result in inaccurate inversions. The estimation technique presented in this paper is highly accurate since it utilizes a 3-D beam model which accounts fully for diffraction effects and other geometrical and experimental parameters. Furthermore, the air-coupled nature of the experiment enhances the estimation accuracy since it minimizes the couplant loading effects. A significant feature of this technique is its high sensitivity to shear stiffness parameters which are generally difficult to obtain. This technique has been successfully used to obtain stiffness parameters for both isotropic and anisotropic plates with single or multilayer structures