Metallic intramedullary nails are the “gold standard” implant for repairing femur shaft fractures. However, their rigidity may eliminate axial micromotion at the fracture (causing delayed healing) and they may carry too much load relative to the femur (causing “stress shielding”). Consequently, some researchers have proposed fiber-reinforced composite nails, but only one evaluated cyclic fatigue performance. Therefore, this study assessed the cyclic fatigue response of a carbon fiber/epoxy nail with a novel ply stacking sequence of [0₂/-45/45₂/-45/0/-45/45₂/-45₂/45₂/-45/90₂] previously developed by the present authors. Nails were cyclically loaded in tension-tension at 5 Hz with a stress ratio of R=0.1 from 30% - 85% of the material's ultimate tensile strength (UTS). Thermographic stress analysis, rather than conventional fatigue testing, was used to obtain high cycle fatigue strength (HCFS), below which the nail can be cyclically loaded indefinitely without damage. Also, the mechanical test machine's built-in load cell and an extensometer were used to create stress-strain curves, from which the change in static E^O and dynamic E* moduli were obtained. Results showed that HCFS was 70.3% of UTS (or about 283 MPa), while E^O and E* remained at 42 GPa without any dRegradation during testing. The current nail shows potential for clinical use.

金属髓内钉是修复股骨干骨折的“金标准”植入物。然而，它们的刚性可能会消除骨折处的轴向微动（导致愈合延迟），并且它们可能相对于股骨承受过多的负荷（导致“应力屏蔽”）。因此，一些研究人员提出了纤维增强复合钉，但只有一个评估了循环疲劳性能。因此，本研究评估了具有 [0 ₂ /-45/45 ₂ /-45/0/-45/45 ₂ /-45 ₂ /45 ₂的新型层堆叠顺序的碳纤维/环氧树脂钉的循环疲劳响应/-45/90 ₂] 以前由本作者开发。钉子以 5 Hz 的张力-张力循环加载，应力比为 R=0.1，为材料极限拉伸强度 (UTS) 的 30% - 85%。热成像应力分析，而不是传统的疲劳测试，用于获得高循环疲劳强度 (HCFS)，低于该强度，钉子可以无限期地循环加载而不会损坏。此外，机械试验机的内置称重传感器和引伸计用于创建应力应变曲线，从中获得静态E ^O和动态E * 模量的变化。结果表明，HCFS 为 UTS 的 70.3%（或约 283 MPa），而E ^O和E* 在测试期间保持在 42 GPa，没有任何 dRegradation。目前的指甲显示出临床使用的潜力。