High-speed infrared thermography for in-situ damage monitoring during impact test

The impact damage tolerance remains for laminated composite materials one of the critical step in the design of aeronautical structures. Due to couplings between the different involved damage mechanisms (transverse cracks, delamination, fibre failure), the determination of the damage scenarios is still very challenging considering only post-mortem controls, such as C-Scan or more recently CT-Scan. Therefore, the present study is dedicated to the real time measurement of the evolution of different damage mechanisms during low velocity/low energy impact tests using high-speed infrared thermography. Impact tests at different energy levels were conducted on a T700GC/M21 quasi-isotropic laminate in order to demonstrate for different damage scenarios of increasing complexity the contribution of this measurement technique and to extract valuable information in order to validate simulation. Various post-mortem observation techniques (SEM, C-scan and X-ray tomography) are used in this study to validate and/or determine the chronology of the various damage events identified with infrared thermography measurements. Finally the projected damaged areas have been estimated with IR-thermography at the end of impact tests, based on methodologies available in the literature, and compared with other classical post-mortem measurement methods. This comparison highlights that the assessment of the extent of damage by IR thermography tends to overestimate the extent of damage.