Study on high-cycle fatigue and very-high-cycle Fatigue properties for braided composites

Braided composite materials are widely used in structures such as aircraft engine blades due to their unique advantages of integrity and damage resistance. Their fatigue performance is an important indicator for the development of aircraft engines. This article aims to comprehensively evaluate a high-precision life prediction model suitable for braided composite materials based on low-cycle (<10^5) and high-cycle-fatigue (10^5∼10^7) test results, and then predict and verify the high-cycle and very-high cycle (10^7∼10^8) fatigue performance. By designing tensile, compression, and shear tests both in-plane and out-of-plane, low-cycle and high-cycle-fatigue mechanical performance tests were conducted. Based on fatigue data fitting, the most suitable Weibull life prediction model was selected. The applicability of the model in the very-high-cycle fatigue stage was verified through experiments. The results showed that in the low-high cycle fatigue stage, the deviation between the Weibull model life prediction and the experimental life was concentrated in the 3.5-fold dispersion band, while 2-fold fatigue dispersion band near the 10^8 very-high-cycle fatigue zone, and in the 10^7–10^8 high cycle fatigue life stage, braided composite materials exhibited a horizontal platform similar to traditional fatigue limits.