The fatigue properties of 14 wt-% short glass fiber reinforced polyetheretherketone (PEEK–GF14) have been investigated in the high and very high cycle fatigue (VHCF) regime. Experiments were performed at a load ratio of –1 with servohydraulic and electrodynamic equipment at cycling frequency 10–20 Hz, and with ultrasonic equipment at 19 kHz. A new specimen geometry has been developed that allows ultrasonic tests up to high stress amplitudes. The same specimen shape was used in both testing series to exclude size effects, which enabled to focus on the influence of cycling frequency and testing technique. Ultrasonic fatigue testing with intermittent loading served to avoid heating of specimens. The S-N curves measured at 10–20 Hz and 19 kHz show a similar slope exponent (i.e., 10 % deviation). Mean S-N curve determined with ultrasonic equipment is shifted to slightly lower stress amplitudes, which may be attributed to statistical scatter. PEEK–GF14 does not show a fatigue limit and failures still occurred above 109 cycles. The VHCF strength of PEEK-GF14 is approximately two times higher compared with unreinforced PEEK. Fractographic investigations revealed fiber fracture and, less frequently, fiber pull-out.

中文翻译：

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短玻璃纤维增强聚醚醚酮 （PEEK） 的极高周疲劳性能


在高周疲劳和甚高周疲劳 （VHCF） 状态下研究了 14 wt-% 短玻璃纤维增强聚醚醚酮 （PEEK-GF14） 的疲劳性能。实验是在 –1 的负载比下使用伺服液压和电动设备以 10-20 Hz 的循环频率进行，并使用超声波设备以 19 kHz 的频率进行实验。开发了一种新的试样几何形状，允许在高应力幅值下进行超声检测。在两个测试系列中使用相同的试样形状以排除尺寸效应，从而能够关注循环频率和测试技术的影响。间歇加载的超声疲劳测试用于避免试样加热。在 10-20 Hz 和 19 kHz 下测得的 S-N 曲线显示出相似的斜率指数（即 10% 的偏差）。用超声设备测定的平均 S-N 曲线偏移到略低的应力幅值，这可能归因于统计散射。PEEK-GF14 没有显示疲劳极限，并且在 109 次循环以上仍会发生故障。PEEK-GF14 的 VHCF 强度比未增强的 PEEK 高出约两倍。断层学检查显示纤维断裂，较少见的是纤维拉出。