Experimental Evaluation of Global Composite Laminate Stiffnesses by Structural Wave Propagation

Abstract

An experimental method based on a consistent second order theory for flex ural waves in an orthotropic fiber reinforced plate is described. The propagation of struc tural waves allows the accurate evaluation of four elastic constants E22, E33, G12, G13 in a single experiment. The flexural waves are induced centrally with a piezoceramic trans ducer. Phase velocities as a function of frequency are determined from the phase spectra of flexural waves measured with a heterodyn laser-Doppler-interferometer along straight lines through the loading point. The theory is developed by means of asymptotic expan sions of the three dimensional equations of linear elasticity and includes shear deforma tion. The measured behaviour and the accuracy of the moduli is shown to be very satisfac tory and in accordance with theoretical expectations.