NDT thermographic techniques on CFRP structural components for aeronautical application

This paper describes the application of active pulsed Thermography (PT) as a Non-Destructive Test (NDT) method for the investigation of CFRP aeronautical components. The analyzed specimens include T-shaped stringers, previously monitored by ultrasonic analysis, and laminated flat plates with internal production defects. Several set-up tests allowed to identify optimal configurations for the defect detection, according to specimen geometry and defect location. A custom post-processing algorithm has been developed to improve thermographic data for more precise defect characterization, whilst a successive full-field contrast mapping allows to achieve a reliable defect distribution map and a better definition on larger areas. Detection of defects was studied with a specific thermal contrast evaluation, with a suitable choice of undamaged reference area during the transient cooling phase. The influence of heating time and experimental set-up on the thermal contrast results has also been studied; moreover, the ability of thermographic technique to detect real small production defects with accuracy and reliability is verified for CFRP aeronautical components.