SINGLE-SIDED DETERMINATION OF ELASTIC-CONSTANTS OF THICK COMPOSITES USING ACOUSTOULTRASONIC TECHNIQUE

The determination of elastic constants is vital for any in-depth study of material performances. One of the more frequently used methods for elastic constant determination involves ultrasonic velocity measureme nts. Although this method is convenient in isotropic materials, it inv olves more complicated procedures for anisotropic materials. In this s tudy, a measurement method is introduced that does not require cutting samples for velocity measurements in different directions. This metho d utilizes the acoustoultrasonic technique and deduces the elastic con stants of transversely isotropic materials from the time-of-flight of obliquely reflected echoes which are received by another transducer pl aced on the same surface. Analytical and numerical analyses are descri bed which reveal the sensitivity of the results to different kinds of measurement errors. It is reported that systematic errors are most det rimental to the extraction of elastic constants, and appropriate steps are demonstrated which reduce this kind of error. This method is expe rimentally tested on three unidirectional graphite/epoxy composite pla tes. Three of the elastic constants were found using pulse-echo veloci ty measurements normal to the top surface of the sample plate. The oth er two elastic constants were computed using acoustoultrasonic techniq ue. The results show good agreement with nominal values of elastic con stants obtained by cutting one of the tested samples.