Characterization of failure mechanisms of composite structures subjected to fatigue dominated by the self-heating effect

A self-heating effect in a non-stationary regime is a very dangerous phenomenon occurring in polymeric composites during cyclic loading, which significantly intensifies a degradation process and leads to a catastrophic failure of the loaded structure. In this paper, the authors performed fatigue tests until achieving various self-heating temperature values on the tested specimens' surfaces, and further inspection using the X-ray computed tomography. The developed image processing algorithm allows for extraction and classification of different types of damage. The obtained results allow precise determining of a critical self-heating temperature due to a very high accuracy of the applied method as well as describing in detail a degradation mechanism of a polymeric composite structure subjected to fatigue with the accompanying self-heating effect. It was also possible to combine observed events in the temperature and acoustic emission evolution with an appearance of structural damage in the tested structures and describe a general phenomenology of the degradation process of composite structures working in such conditions. The obtained results allow for improvement of design requirements of composite structures working in mechanical fatigue conditions as well as proper maintenance of composite constructions in order to avoid critical ranges of generated heat during cyclic loading.