Applications of Barker coded infrared imaging method for characterisation of glass fibre reinforced plastic materials

Abstract

Among various widely used thermal non-destructive testing methods, non-stationary thermal non-destructive testing modalities have proved to be an indispensable approach for the inspection and evaluation of various solid materials. These techniques facilitate the use of low peak power heat sources in a moderate time compared with the conventional widely used pulsed and sinusoidal modulated (lock-in) thermographic techniques. In this reported work, Barker non-stationary excitation followed by Hilbert transform-based matched filtering for the detection of subsurface features lying deep inside a glass fibrereinforced plastic test sample is incorporated. Results obtained from this pulse compression approach are less affected by random noise generated inside the test sample during experimentation as well as the variations of surface emissivity over the test sample. A comparison has been carried out among the amplitude, time delay and phase images obtained for the experimentally matched filter data.