Laser Ultrasonic Testing of Highly Attenuative and Weakly Generating Composites

Abstract

Current fighter aircraft contain on the order of 10% composite structure, and future fighter aircraft may contain upwards of 50% composite structure. These structures are often large, complex in shape, and flight critical. Stringent engineering requirements mandate 100% inspection prior to installation of flight critical parts as well as periodic inspections in service. Conventional automated ultrasonic systems have been used by the aerospace industry for inspecting flat or mildly contoured parts in the production environment. These systems are slow, require significant setup time for highly contoured parts, and are generally inappropriate for in-service inspections where access is limited to a single side. Lockheed Martin Tactical Aircraft Systems (LMTAS) has gained extensive practical experience over the past decade applying laser ultrasonic testing (Laser UT) methods to advanced aerospace composite materials (Drake, 1994; Chang et al., 1993). Laser UT greatly reduces the time and cost of inspecting complex composite materials by reducing or eliminating part fixtures and long setup times. It is capable of scanning complex contoured composite structures more than 10-times faster than conventional systems. This paper will address some of the problem areas associated with the laser ultrasonic testing of advanced composite materials.

This work was partially supported by LMTAS IR&D and the Air Force Materials Laboratory, Contract# F33615-92-C-5981.