Evaluation of Global Composite Laminate Stiffnesses by Structural Wave Propagation Experiments

Abstract

An experimental method based on the propagation of structural waves is presented which allows to determine the five most important elastic stiffnesses of an orthotropic plate. In the first part flexural waves are studied. A consistent second order theory which includes shear deformation perpendicular to the middle-plane of the plate is derived by means of the asymptotic expansion of the three dimensional, linear-elastic equations. Phase velocities of flexural waves which are induced centrally with a piezoceramic transducer are determined from the phase spectra of the time signals which were measured with a heterodyne interferometer along straight lines through the loading point. The flexural wave experiments allow to determine four elastic constants with very satisfactory accuracy by only one single measurement. In the second part in-plane shear waves are studied. The measurement of the phase velocity in the principal direction of anisotropy allows to determine the in-plane shear modulus. Thus the five most important moduli of the orthotropic plate are determined.