ABSTRACT
In recent years, anisotropic materials have been attracted lots of interest for various engineering fields. CFRP (Carbon Fiber Reinforced Plastics) is known as one of the anisotropic materials and has been used as a main material of aircraft and as a seismic strengthening member of civil and architectural structures. In general, the Ultrasonic nondestructive Testing (UT) is widely used for material inspection because the UT is portable for ready to use and transport compared to the Radiographic Testing (RT) which can be practiced by only suitably trained and qualified personnel. However, anisotropic materials sometimes make it difficult for inspectors to detect flaws because the phase and group velocities of elastic waves in anisotropic materials depend on their propagation directions. Therefore, a better knowledge of anisotropy is a great help for accurate the UT. In general, it is essential to determine the elastic constants of the anisotropic materials should be inspected in order to understand the anisotropic properties. Several researches about elastic constant estimation methods have been done since decades ago. A problem of conventional elastic constant estimation methods that need to be overcome is that we have to cut the test specimen to investigate the phase velocity of waves propagating in an oblique direction. This disadvantage is not efficient and economic, and should be resolved from the point of view of environmental aspect of waste generation.
