Determination of Microcracking Damage in Composites

There is a need for the nondestructive diagnosis of micro-cracking in the composite skin of a honeycomb sandwich structure used in aircraft and space systems. We propose to use Differential Spectral Interferometry (DSI) as a noninvasive tool to quantifythe location and depth of micro-cracking in the composite skin. In DSI, the sample is irradiated with infrared light, which penetrates into the material. The back-scattered light, when combined with the reference light beam in the interferometer, producesan interference spectral fringe pattern - interferogram - that contains the depth information. The high dynamic range of DSI allows testing of materials which are opaque as seen by eye. We expect that the DSI method can be implemented in a relativelysimple and compact instrument, which can be used independently, or in combination with currently used inspection methods, such as ultrasound techniques. The market is sales of the instrument to the military and commercial organizations for inspection ofmicro-cracking damage in parts and structures made of composite materials. Benefits include enhanced aircraft safety and cost savings resulting from improved quality control during development and manufacture of composite parts and materials.