Increasing aircraft safety with better materials testing
Non-destructive testing (NDT) techniques provide information about potential or existing defects in materials and parts without themselves damaging the parts. NDT is increasingly employed during the development phase in the aeronautics industry, saving valuable time and materials. Optical non-contact technologies such as infrared thermography and shearography/holography have been widely employed. The former senses temperature distribution patterns that can be compared to temperature 'signatures' for identification of defects. The latter employ lasers to reveal target deformation and translation responses to an applied stress. These techniques enable wide-field assessment without dismantling, but typically rely on two different sensors. Using state-of-the-art components, scientists are developing a novel one-sensor system with a shearography/holography sensor operating in the spectral range of an infrared thermographic camera. EU funding of the Fantom project is supporting scientists in their endeavour to decrease uncertainty, inspection time (one set-up and calibration instead of two) and post-processing to correlate deformation/temperature information. In addition, researchers are extending the range of displacement/strain measurement by a factor of 20, enabling an assessment of large deformations that was previously inaccessible outside controlled laboratory conditions. Following selection of the appropriate holographic technique (electronic speckle-pattern interferometry (ESPI)) for combination with thermography (using a long-wave infrared laser (LWIR)), Fantom developed and built a portable prototype. It was tested and shown to enable visual inspection of large-scale deformations induced by high levels of disturbance, filling the sensitivity gap in current technologies. In a full-scale industrial case study of a large composite in a hangar, Fantom technology demonstrated enhanced defect detection capability when compared to two separate sensors. Fantom has successfully delivered a mobile instrument capable of simultaneously measuring temperature and deformation with improved probability of defect detection over an extended deformation range. Fantom should be useful in aircraft development and maintenance as well as in numerous other sectors where large composite components are employed. These include the shipping, automotive and civil engineering markets.
