Characterization of guided wave propagation in aircraft structures

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Structural health monitoring (SHM) is a major area of interest for the aerospace community, especially considering aging aircraft where the growing maintenance costs estimated to $10,4 billion worldwide annually. The 5 to 10 years goal of the industry is to deploy SHM systems which will 1) meet the in-service inspection requirements with sensors permanently installed on the structure and 2) provide economic benefits compared to the baseline inspection methods. Strategies using guided wave propagation have been proposed for embedded monitoring of airframe structures. However, wave propagation and interaction with defects in complex structures is addressed in the literature only for specific and limited number of components and types of defects. For example, interaction with cracks in metallic joints and debonding in composite joints has been investigated to some extent. The objective of this knowledge-gap based research is to provide the industry with an extended knowledge base for a variety of basic aircraft structures, or standards, from which the guided wave propagation and interaction with defects for other specific structures could be inferred from. The knowledge base will contain parameters such as the type of modes propagating in the structures or interacting with defects, the attenuation of the waves, the spatial pattern of the waves and the dispersion curves. The specific objectives of the project are: 1) develop a standard process to characterize guided wave propagation, 2) develop a knowledge base of guided wave characteristics for a variety of common aircraft structures, 3) develop a knowledge base of guided wave interaction mechanisms with damage for a variety of common aircraft structures and 4) propose SHM design criteria for guided waves in aircraft structures. Such a knowledge base would allow industrial partners to optimize sensing configuration and minimize development time, by reducing required testing for validation and qualification of SHM applications for damage monitoring.