Non-destructive evaluation of composite repairs by using infrared thermography

Abstract

Composite structures are found in modern aircraft designs ranging from air transport to general aviation. Maintenance repair technology varies for each original equipment manufacturer and aircraft type. This research reports on two different composite repair methods commonly used within the composite aviation industry and how they compare when inspected with transient infrared thermography non-destructive evaluation technique. Composite sandwich test coupons made with carbon fiber laminate, nomex honeycomb, and glass fiber laminate were used for this work. Impact damages were generated in the sandwich test coupons and repairs were conducted by following repair procedures of two leading general aviation composite aircraft manufactures. During the repair process, controlled flaws were also induced to simulate bad repairs with weak bond areas, disbonds, and excessive porosity. During transient infrared thermography, several patches were identified that contained wrinkles, porosity, and disbond defects in the repaired panels. The indications were evaluated utilizing the time vs. temperature plot curves and profile data. The porosity indications displayed significant variations compared to the surrounding areas and were subsequently deemed defects as a result of the data.