Thermomechanical fatigue behaviors and failure mechanism of 2.5D shallow curve-link-shaped woven composites

Thermomechanical fatigue (TMF) performance is one of the most challenges for aero-engine materials. This work experimentally elaborated the in-of-phase (IP) TMF behaviors and failure mechanism of high-temperature resistant 2.5D woven composites (2.5DWCs) for the first time. In this study, both fatigue load and thermal load varying from 160 degrees C to 260 degrees C are synchronously imported in the form of trapezoidal wave. An experimental platform consisting of quasi-static mechanical tester, strain collection device, heating/cooling equipment and temperature control system was firstly established. The relationship between stress level and TMF life was obtained. The fracture morphologies were investigated using scanning electron microscope (SEM) and X-ray computed tomography (Micro-CT). Results show that the TMF behaviors of 2.5DWC exhibit a low cycle fatigue characterization with a fatigue limit of 0.75 stress level. The hysteresis loops gradually shift to the right, confirming an elongation of specimen during the TMF. It indicates a reduction of inclination angle of warp yarns. Particularly, the failure behavior is fiber-dominated brittle fracture mode, without clear necking phenomenon. The fiber pull-out length and the extensive debonding are more severe than those failed in the static loading. Finally, a probable failure mechanism for the TMF behaviors of 2.5DWC is proposed.

Automated summary

This study experimentally elaborated the in-of-phase thermomechanical fatigue (TMF) behaviors and failure mechanism of high-temperature resistant 2.5D woven composites for the first time. The results showed that the TMF behaviors of the composites exhibited low cycle fatigue characterization and the fiber pull-out length and extensive debonding were more severe than those failed in static loading.