Detection of subsurface defects using a hybrid heating and cooling imaging technique

Abstract

A middle infrared imaging technique combining sequential heating and cooling of the material is shown to detect internal defects in composite materials. A low power flash lamp is used as the heat source to raise the temperature of the material above the ambient temperature. Alcohol is spread on the front surface of the heated sample to cause rapid cooling and removal of the thermal wall. This technique induces thermal waves in the composite material, reduces the diffusive photons, and enables recording better images of internal defects by a mid-infrared camera. The technique provides substantial improvement over existing methodologies currently in use for nondestructive evaluation of subsurface defects and cracks in materials. © 2006 American Institute of Physics.