Electronic shearography with thermal loading for detecting debonds in thick polyurethane/steel panels for marine applications

We demonstrate that electronic shearography with thermal loading can be effectively applied to the nondestructive detection of debonds in thick polyurethane/steel structures usually employed in the hulls of military ships. A compact fiber-optics shearographic interferometer has been developed that allows remote full-field measurements in real time. Three known debonds in a polyurethane/steel test panel are clearly detected by observing their increased deformation as they cool down after the application of a thermal load. It is also shown that the debond edges can be identified. The results obtained indicate that the shearographic interferometer is well-suited for field detection and sizing of debonds in such panels. Future refinements to the system will include the use of high-power, pulsed illumination for the imaging of large areas and consequent real-time mapping of possible debonds.