Infrared thermography (IRT) inspection of ballistically impacted carbon fibre-reinforced polymer (CFRP) laminates designed for self-healing behavior

Abstract

In recent years there has been a strong interest in thermoplastic polymers with self-healing behavior, which after suffering mechanically-induced damage they self-repair via macromolecular rearrangements enabled by the energy generated in the damage process itself, or, alternativelly, via activation energy provided by an external source. The use of film-shaped self-regenerating polymers in alternating layers with high-performance continuous fiber-reinforced thermosetting polymer matrix laminates is considered particularly attractive in the mitigation of impact damage in high-demanding components and structures, insofar as the self-healing films might at the same time toughen the base fibrous thermosetting matrix laminate composite (which is mechanically resistant and stiff, but intrinsically brittle and therefore subject to catastrophic failures) and provide immediate or subsequent self-repairing according to the above mentioned mechanisms. In this research project, InfraRed Thermography (IRT) technique is proposed for both the nondestructive inspection of ballistic impact damage in a hybrid laminate (such as described above) tested at low temperatures (typical of the altitudes in which modern civil and military aircrafts travel), and the subsequent assessment of the degree of success of thermally-activated self-healing process by external heating source (resistive furnace or infrared radiation). The need for developing reliable methodology and protocol from a technologically advanced nondestructive inspection technique emerged from the discovery (during the ongoing IC-FAPESP project of the proponent) that more traditional techniques, such as ultrasound and eddy current, not proved efficient for the inspection of the hybrid composite laminate due respectively to the high sonic attenuation and the poor electrical conductivity of the thermoplastic self-healing film. (AU)