Active Infrared Thermography Technique for the Non Destructive Testing of Composite Material

Delamination is one of the most common defects in laminate composite materials. To detect delaminations, different non-destructive test methods such as infrared thermography methods are currently widespread for non-destructive inspection, recommended for evaluating composite materials mostly in the active variant. The principle behind infrared thermography consists in highlighting the relevant differences of temperature, by comparing the temperature of the area without defect to the defected area temperature. Active infrared thermography refers to the group of methods employed to inspect the integrity of materials or systems through the use of an external energy source and an infrared detector. The paper presents several experimental examples concerning the use of active thermography in the non destructive evaluations of composite materials. The paper presents the analysis of results obtained by active infrared thermographic testing of E glass woven (0, 90) reinforced polymer plates of eight plies containing artificial delaminations. For this study, number of composite plates were manufactured with different known depths of delamination implanted using Aluminium foil coated with special wax and different thickness of delamination embedded at same depth. The aim of the present paper to investigate experimentally the ability of active thermography to detect the delamination based on its depth location and thickness. Thermal images obtained by experiments using infrared camera were used to extract surface temperature profiles above the delaminated and non-delaminated surfaces on the specimens. The dependency of thermal contrast on delamination depth and delamination thickness was also investigated.