Application Of Laser-Based Methods And Finite Element Analysis To Bond Verification Of Space Shuttle Tiles


This paper describes a novel application of a laser-based vibration measuring system and finite element modeling to evaluate the bond condition of Space Shuttle thermal protection system tiles. This application is based on characterizing the vibrational response of tiles when excited by an audible acoustic energy. Finite element models for tile assemblies which are comprised of tiles, SIP, and RTV layers attached to the Orbiter aluminum skin are first developed. The mathematical model considered the actual orthotropic material properties, different geometrical configurations as well as different bond conditions. The tiles' natural frequencies and mode shapes are then determined and their frequency responses due to simulated sound pressure are computed. The computed frequency response of a tile having a disbond indicates a decrease in its natural frequencies. This can be used to quickly identify the disbonded tiles. However, the exact size and location of the disbond are determined from the computed rigid-body vibrational modes. The finite element results are compared with experimentally determined frequency responses of a 17-tile test panel, where a rapid scan laser system was employed. An excellent degree of correlation between the mathematical simulation and experimental results is realized. The paper also reports on laser-based modal and shearographic testing performed on tiles of Space Shuttle Columbia. Again, the results demonstrate that experimental modal analysis, when combined with finite element modeling, can be successfully used as a reliable nondestructive, non- contact technique for tile bond verification.

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Publication Title

Proceedings of SPIE - The International Society for Optical Engineering



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Document Type

Article; Proceedings Paper



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Socpus ID

0027870364 (Scopus)

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