Rapid Characterization of the Degradation of Composites Using Plate Waves Dispersion Data

摘要

NDE methods are needed to determine the structure integrity, stiffness and durability (residual life) of structures and they can be extremely useful in assuring the performance of structures using smaller safety factors. While the integrity and stiffness can be extracted directly from NDE measurements, strength and durability can not be associated with physical parameters and therefore, cannot be measured by NDE methods. Specifically, NDE methods are developed to detect and characterize flaws and to determine the material properties of test specimens. For many years, composites as multi-layered anisotropic media, have posed a challenge to the NDE research community. Pulse-echo and through-transmission are the leading methods that are used in practice to evaluate the quality of composites. However, these methods provide limited and mostly qualitative information about the material properties and many defects. Following the discovery of the LLW and the Polar Backscattering phenomena in composites [1,2], numerous experimental and analytical studies have taken place using obliquely insonified ultrasonic waves [3–5]. These studies led to the development of effective quantitative NDE capabilities to determine the elastic properties, to accurately characterize defects and even to evaluate the quality of adhesively bonded joints [6, 7]. In spite of the progress that was made both theoretically and experimentally, oblique insonification techniques are still academic tools and have not yet become standard industrial test methods for NDE of composite materials. The authors investigated the issues that are hampering the transition of these methods to the practical world of NDE and are involved with extensive studies to address these issues. This paper covers the progress that was made by the investigators in tackling the theoretical and experimental issues to solidify the foundation of the techniques and their transition to practical NDE tools.