The Ultrasonic Measurement of Elastic Constants of Structural FRP Composites

Interest in fiber reinforced polymeric (FRP) composites for structural highway applications has generated the need for reliable techniques which may be used to measure all of the elastic constants of these materials. Mechanical techniques may only be used to measure some of the engineering constants of these anisotropic materials due to the geometry of the pultruded members. Further, mechanical tests are destructive in nature. Ultrasonic techniques are uniquely qualified for the nondestructive measurement of all of the elastic constants of these materials. This paper presents the results of three ultrasonic techniques. The first of these is an immersion technique, similar to that presented by Gieske and Allred [1]. The last two techniques were developed specifically for this research, and implement optical generation and detection of surface acoustic waves for the measurement of some of the elastic constants. The results of the various techniques are compared to each other, as well as to results from mechanical tests.