USE OF PLATE BENDING WAVES FOR ELASTIC PROPERTY DETERMINATION OF POLYMERS

A novel method is described for determining elastic properties of both reinforced and isotropic plastics through measurement of the velocity of plate bending (Lamb) waves of frequency around 100 kHz. The method is applicable to test pieces or fabricated articles in the form of a plate or shell of uniform thickness. Lamb waves may be launched and received at a single surface and travel with a velocity which is sensitive to in-plane tensile properties. There is therefore scope for using the method non-destructively for measuring the tensile stiffness in the direction of reinforcement in fibre reinforced plastics. The capabilities and limitations of the technique are demonstrated through measurements made on unreinforced plastics, an aligned carbon fibre reinforced material and two carbon fibre reinforced cross-piy laminates.