Characterization of Composite Laminates using Combined LLW and PBS Methods
Application of composites to structural components of defect-critical systems, such as aircraft, requires adequate nondestructive evaluation (NDE) capability. NDE methods must be able to detect and characterize defects as well as determine the material properties. Various methods have been developed in recent years to support different aspects of this general need. Ultrasonic pulse-echo and through-transmission as well as radiography are widely used during manufacturing and service. By comparing the response to reference standards, these methods are used qualitatively to identify gross defects and areas with a questionable quality. This application does not take advantage of the quantitative NDE capability that has become available in recent years [see for example 1–4]. Examples of such methods are the leaky Lamb waves (LLW) and polar backscattering (PBS). Significant progress has been made in recent years in the theoretical analysis of the wave behavior in such transversely isotropic layered media. These methods can be used (a) in conjunction with a C-scan system to provide images of various type of defects , or (b) through various measurements to characterize defects and determine the material elastic properties . Present work is directed toward combining the use of both LLW and PBS for material characterization.