Abstract: For the application of filament winding carbon fiber reinforced polyphenylene sulfide (T700/PPS) thermoplastic composites, the NOL ring test was used to study the tension-tension fatigue behavior for the first time and a life prediction method was proposed. Based on the self-developed thermoplastic composite filament winding platform with in-situ consolidation, NOL rings were prepared with T700/PPS prepreg by laser-assisted heating. According to the standard NOL ring tensile test, the result of average static tensile strength was 2 438.35 MPa, the dispersion coefficient was 2.0% and the failure mode was brittle fracture. Based on static strength data, the stress level of the fatigue test was determined. Aiming at the characteristics of the ring-shaped test piece, a “split ring” fatigue fixture was designed to carry out the tension-tension fatigue test of the NOL rings under different stress levels, then the thermal behavior during the fatigue cycle was analyzed with the help of infrared thermal imager and the failure modes was captured. In view of the large discreteness of fatigue life data, a convenient and efficient life prediction algorithm was proposed: The fast data screening was realized by K-means clustering, and the grey GM (1,1) model was constructed to predict the fatigue life of NOL rings and draw the S-N curve. It was found that when the stress level is lower than 47% of the static strength, the fatigue life will exceed 10⁷ times and enter the infinite fatigue life stage, which provides support for the life design of high-speed rotating parts and thermoplastic pressure vessels manufactured by filament winding.

Key words: thermoplastic composites, fatigue test of NOL rings, thermal behavior, failure modes, data screening methods, life prediction