Large-Scale Laser Ultrasonic Facility for Aerospace Applications

Abstract

The use of composite materials for aerospace applications has markedly increased over the past two decades. Typically, a large percentage of composite aircraft components are fatigue and fracture critical, necessitating 100% inspection coverage. For composite materials, ultrasonic testing is the method of choice for detecting manufacturing defects which could lead to catastrophic failure during flight. As composite usage and part complexity increase, greater demands are placed on ultrasonic inspection systems. Projections of future composite usage (e.g. Joint Strike Fighter (JSF) program) show that the inspection workload may push current conventional automated ultrasonic inspection systems beyond practical limits. Conventional systems are typically 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. Laser ultrasonic testing (Laser UT™) on the other hand offers many advantages over conventional automated ultrasonic systems: (1) the method is non-contact, requiring no couplants, (2) it can rapidly scan large areas, (3) it is able to inspect at angles far off normal, (4) it does not require expensive part fixtures, and (5) prior knowledge of the surface contour is not required. The optical scanning techniques used in make it capable of testing complex composite structures at speeds that cannot be matched by conventional mechanical scanning systems. These advantages in turn will reduce inspection costs and increase production throughput by as much as a factor of 10. Figure 1 illustrates the time savings of Laser UT™ over conventional UT as a function of part complexity.