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

Criticality of the Self-Heating Effect in Polymers and Polymer Matrix Composites during Fatigue, and Their Application in Non-Destructive Testing

“…In order to investigate the fracture mechanisms occurring during the fatigue of PMCs accompanied with deep self-heating, and to analyze their influence on the criticality of a degradation process, an additional study was performed on a set of specimens with various degrees of degradation, prepared in the same way as the previous usage of X-ray Industrial Computed Tomography (ICT) [145]. The X-ray ICT tests allowed for 3D representations of fractured specimens to be obtained, and observation of the initiation of cracking due to self-heating.…”

“…The selected results of the processed tomograms are presented in Figure 16. The full set of processed tomograms can be found in [145].…”

“…This difference can be explained by the low thermal conductivity of industrial polymers in general, which causes heat to be stored inside the structure. The tomographic tests of specimens performed at various stages of degradation due to self-heating [145] confirmed that the initiation and propagation of damage starts on the upper and lower surfaces (see Figure 16), which is a result of the highest tension–compression stresses on the surfaces of a cyclically bent structure. Considering a fully reversed bending mode, the stresses in the midplane of a cyclically loaded structure are the lowest in the z -coordinate (thickness direction).…”

Determination of fatigue limit of polymeric composites in fully reversed bending loading mode using self-heating effect

“…24 The occurring micro-cracks finally transform into a macro-crack and initiate additional heating source originating from the friction of the surfaces in the crack gaps. 25 The observed character of the selfheating temperature evolution leads to the three-phase model observable both for metals 2,4,[6][7][8]10 as well as for polymers and polymer-based composites. 14,17,26,27 One should consider that in the case of occurrence of the self-heating, the complex process of the fatigue degradation of polymer matrix composites can be reduced to the analysis of degradation of a polymeric matrix only.…”

“…The current authors' studies are focused on the estimation of the criticality of the self-heating temperature for polymeric composites. According to the results of performed experimental studies using various approaches, [24][25][26][27][28] it was found that a specific self-heating temperature value exists. After exceeding this value the structural degradation in the form of micro-cracking of a polymeric matrix starts.…”