Quantitative Thermal-Wave Measurement of Defects in Composite Aircraft Structures

摘要

We describe novel thermal wave imaging techniques that are capable of making quantitative measurements of both the lateral sizes, and the depths of defects in composites. Examples include natural and engineered defects in C-141, C-130, and F-15 structures. Among the defects are examples of the intrusion of fluids into honeycomb core. We also describe a wave algorithm that is capable of distinguishing between different fluids, e.g. hydraulic fluid or water, within the honeycomb. These algorithms depend on tracing the temperature-time behavior on the surface of the composite, after a short pulse of heat has been applied. This technique uses flash heating of a large area, followed by imaging with a snapshot-mode, focal-plane-array infrared camera, operating in the 3 mu m-5mu m spectral range.