An innovative approach for the elastic characterization of anisotropic materials

The present paper describes an experimental procedure whereby the elastic constants of a thin plate can be determined. The procedure allows to determine the elastic constants of isotropic materials (metals and ceramics) and orthotropic materials (composite laminae) or the flexural compliance of completely anisotropic uncoupled materials (the most of composite laminates). The loading device allows to align the specimen with the respect of the constraint positions and to obtain an accurate measurement of the applied load. A speckle interferometer was used to measure the whole field of the out-of-plane displacements; the interferometer is equipped with a PZT actuator necessary to perform the phase-shifting procedure and to obtain a valid information at any pixel of the image. The experimental procedure is entirely controlled by a personal computer operating in the National Instruments LabVIEW® environment. By means of the virtual instrument developed on purpose it is possible to move the PZT actuator and to acquire, by a CCD camera, the intensity patterns of the light scattered from the surface under test. Two numerical differentiation, performed on each phase map, allows to obtain the whole field of the curvatures from which, by an analytical integration, the average strain components are computed. All the numerical operations performed on the phase maps were carried out in Mathematica® environment.