POTENTIAL CAPABILITIES OF TRANSMISSION ULTRASONOGRAPHY FOR COMPOSITE-MATERIALS

The ultrasonic inspection of a composite through an air gap is studied numerically and experimentally. Refraction at the air-composite inter face (the composite is modeled by a transversely isotropic medium) is investigated both for plane waves and for an ultrasonic beam of restri cted width. It is established that the transmission coefficient of a c onfined ultrasonic beam has a local maximum at an entry angle of appro ximately 13-degrees. The result is confirmed experimentally on polymer fiber-reinforced composite slabs. Numerical investigations show that the method attains maximum resolution when the ultrasonic beam is orie nted at the angle determined in the study.