Surface Wave Utility in Composite Material Characterization

Abstract

A surface wave velocity measurement technique is used to supply supporting measurements in the computation of elastic constants for practical nondestructive evaluation of composite materials. Theoretical modeling work is carried out to illustrate the surface wave velocity changes as a function of angle with respect to the axes along the fibers of a unidirectional graphite epoxy composite material for a variety of different problems, including porosity (PC) changes, fiber volume fraction (FF) changes, and delamination. Experiments are conducted on two unidirectional reinforced composites and a (O-90), cross ply graphite epoxy laminate to illustrate the surface wave velocity measurements and the inverse computation procedure for evaluation of the stiffness coefficients. Variations of the feature values in the stiffness matrix are also discussed for inhomogeneities, delaminations through cracking, and large defects.

Nondestructive Evaluation of Laminated Composites Using Rayleigh Waves

“…In order to attain the resolution, repeatability, and accuracy that are required to measure a 10% change in Rayleigh wave speed, the approximate change caused by a resin-rich area [12], a fixture system was developed. Simplicity was essential for this system so that Rayleigh wave velocities could be consistently measured.…”