Detection and Characterization of Mechanical Impact Damage Within Multi-Layer Carbon Fiber Reinforced Polymer (CFRP) Laminate Using Passive Thermography

With the increasing application of CFRP laminate, there is an `urgent need for the rapid, visual, and non-intrusive method to `detect mechanical impact damage. Passive thermography has been proven `as a promising alternative to traditional nondestructive test technique by `imaging the surface temperature difference of target with the advantages of `real-time, non-intrusive, full-field, and visual `results. Therefore, the aim of this paper is to `characterize the impact damage types using passive thermography. To `this goal, several specimens are subjected to impact test with `different energies of 5, 10, 15, 20, `30, and 36 J and monitored by infrared camera. Then, active `pulse thermography, SEM, and ultrasonic C-scanning are applied to `detect the specimens respectively and the corresponding detection results `are comparatively analyzed. On this basis, the impact damage `types of CFRP are characterized. The obtained results show that `different impact damage types occur under the different impact energies and `can be characterized in the thermographic image. In detail, the `matrix cracking, fiber rupture, and delamination can be characterized as `hot spot with straight line shape along the fiber direction, hot spot `with straight line shape perpendicular to the fiber direction and hot spot `with irregular block shape respectively, which can facilitate the `identification of impact damage mode and the evaluation of damage `degree.