Impact damage assessment in polymer matrix composites using self-heating based vibrothermography

Low-velocity impact damage (LVID) is one of the most dangerous damage types appearing in polymeric composite structures during their operation, since they are invisible or barely visible on a surface, while inside a structure they can exist in a form of extended delaminations as well as matrix and interface cracks. According to damage tolerance and condition-based monitoring philosophies applied during maintenance of aircraft structures damage should be detected and identified in a possibly early stage of its development, especially LVIDs. The currently being developed non-destructive testing method, the self-heating based vibrothermography (SHVT), is a promising approach for damage detection and identification in polymeric composite structures, which is based on hysteretic heating of a polymeric matrix used here as a thermal excitation for the method, and is applicable especially in the cases when a direct access to a tested structure is limited or impossible. In this paper, the authors examined the sensitivity of SHVT to LVIDs considering various shapes of impactors and various impact energies. Moreover, the extended study on damage detectability enhancement was performed. The obtained results reveal acceptable detectability of LVIDs using SHVT, while the applied enhancement methods allow for a significant improvement of the damage detectability and quantification.