## 5 Conclusions  
According to the rheological theory, the dimensionless temperature jump at the critical moment was calculated with the singular integral equation. The theoretical temperature rise was compared with the measured temperature rise, which was recorded by an infrared thermal camera at the critical moment during the process of tensile fatigue test. The relative error between the measured and calculated value was less than 7%, which indicated that the rules of temperature rise during the process  
Figure 10: Temperature rise vs. time graph. (**a**) Comparison of the calculated and measured temperature jump of specimen A1; (**b**) Comparison of the calculated and measured temperature jump of specimen A2. of air bubble defect evolution can be revealed by the functional relation between the temperature and the stress at the critical moment when the air bubble evolved into crack under external load. As shown in the infrared thermal images, different fiber distributions had different sensitivities to air bubble defect. The specimen with fiber orientation [\(-\)45/45]s, ply angles had more crack propagation paths and directions, which caused the thermal energy to be widely distributed, and all the traverse fibers of the specimen were fractured in the end. As for the specimen with [0/90]s ply angles, the thermal dissipation mainly concentrated upon the fracture location of longitudinal fibers around the air bubble. The temperature of other parts slightly increased and the distribution was uniform. Thus, the laminates with [0/90]s ply angles were more favorable in maintaining the structural stability. By comparing the temperature changing regularities of defective and indefective specimens under the same external load, it can be illustrated that the thermal dissipation of air bubble defect was faster than that of the specimen without defect, which caused a higher rate of temperature rise of the specimen containing defect. During the process of evolution of air bubble defect, the thermal dissipation of structure that was caused by the friction between fibers and matrix under tensile load gradually increased and the temperature increased. Thus, the infrared thermal imaging technology can be used to detect the process of air bubble defect evolution and recognize the critical state. By experiment and contrastive analysis of micrographs, a result was obtained that the slippage between fibers and matrix as well as the interface debonding were caused by the air bubble. With the increasing load, the length of interface debonding increased and the stress disturbance transferred to the fibers around the air bubble. The thermal dissipation of structure increased, which was caused by the friction between matrix and fibers under tensile load. The temperature kept increasing and the structure deformation occurred, the bubble evolved into crack in the end. The individual contributions of authors are specified as follows. conceptualization, B.Z. ; methodology, B.Z. ; software, X.Z. ; validation, B.Z., X.Z. and H.L. ; formal analysis, X.Z. ; investigation, X.Z. ; resources, H.L. ; data curation, X.Z. ; writing--original draft preparation, X.Z. ; writing--review and editing, B.Z. ; visualization, X.Z. ; supervision, B.Z. ; project administration, B.Z. ; funding acquisition, H.L. This research was funded by \"National Natural Science Foundation of China, grant number 51575361\", \"Key Laboratory of Vibration and Control of Aero-Propulsion System Ministry of Education, Northeastern University, grant number VCAME201905\" and \"Project of Innovative Talents in Colleges and Universities of Liaoning Province, grant number 2017 737 (006973, 2018640230)\". This research was funded by National Natural Science Foundation of China (Grant No. 51575361) and by Key Laboratory of Vibration and Control of Aero-Propulsion System Ministry of Education, Northeastern University (Grant No. VCAME201905). This project was also supported by Project of Innovative Talents in Colleges and Universities of Liaoning Province (Grant No.