Development and trials of through skin sensing of aircraft fixtures using pulsed thermography

This work evaluates the potential of pulsed – transient thermography for locating fixtures beneath aircraft skins in order to facilitate accurate automated assembly operations. Representative aluminium and carbon fibre aircraft skin-fixture assemblies were modelled using ThermoCalc-3D. The assemblies were also experimentally investigated with the ThermoScope system and a custom built system incorporating a miniature un-cooled camera. Modelling showed that the presence of an air gap between skin and fixture significantly reduced the thermal contrast developed, especially in aluminium. Experimental results from the ThermoScope system show that fixtures can be located to accuracies of 0.5 mm. Preliminary images from the custom system are superior to the ThermoScope, and optimisation is expected to lead to further improvements.