Carbon-fiber reinforced (CFR) PEEK implants are used in orthopedic applications ranging from fracture fixation plates to spinal fusion cages. Documented implant failures and increasing volume and variety of CFR PEEK implants warrant a clearer understanding of material behavior under monotonic and cyclic loading. To address this issue, we conducted monotonic and fatigue crack propagation (FCP) experiments on orthopedic grade unfilled PEEK and two formulations of CFR PEEK (PAN- and pitch-based carbon fibers). The effect of annealing on FCP behavior was also studied. Under monotonic loading, fiber type had a statistically significant effect on elastic modulus (12.5 ± 1.3 versus 18.5 ± 2.3 GPa, pitch versus PAN CFR PEEK, AVG ± SD) and on ultimate tensile strength (145 ± 9 versus 192 ± 17 MPa, pitch versus PAN CFR PEEK, AVG ± SD). Fiber type did not have a significant effect on failure strain. Under cyclic loading, PAN CFR PEEK demonstrated an increased resistance to FCP compared with unfilled and pitch CFR PEEK, and this improvement was enhanced following annealing. Pitch CFR PEEK exhibited FCP behavior similar to unfilled PEEK, and neither material was appreciably affected by annealing. The improvements in monotonic and FCP behavior of PAN CFR PEEK is attributed to a compound effect of inherent fiber properties, increased fiber number for an equivalent wt% reinforcement, and fiber aspect ratio. FCP was shown to proceed via cyclic modes during stable crack growth, which transitioned to static modes (more akin to monotonic fracture) at longer crack lengths. The mechanisms of fatigue crack propagation appear similar between carbon-fiber types.

碳纤维增强（CFR）PEEK植入物可用于整形外科，从骨折固定板到脊柱融合器。有记录的植入物故障以及CFR PEEK植入物体积和种类的增加，保证了对单调和循环载荷下材料行为的更清楚的了解。为了解决这个问题，我们在整形外科级未填充PEEK和两种CFR PEEK配方（PAN和沥青基碳纤维）上进行了单调和疲劳裂纹扩展（FCP）实验。还研究了退火对FCP行为的影响。在单调加载下，纤维类型对弹性模量（12.5±1.3与18.5±2.3 GPa，沥青与PAN CFR PEEK，AVG±SD）和极限抗拉强度（145±9与192±17 MPa，沥青）有统计学意义的影响相对于PAN CFR PEEK，AVG±SD）。纤维类型对破坏应变没有显着影响。在循环载荷下，PAN CFR PEEK与未填充和沥青CFR PEEK相比，对FCP的抵抗力增强，退火后这种改善得到增强。沥青CFR PEEK表现出的FCP行为类似于未填充的PEEK，并且两种材料均未受到退火的明显影响。PAN CFR PEEK的单调性和FCP行为的改善归因于固有纤维特性，等效当量wt％增强纤维数量增加和纤维长径比的复合效应。结果表明，FCP在稳定的裂纹扩展过程中以循环模式进行，并在较长的裂纹长度处转变为静态模式（更类似于单调断裂）。疲劳裂纹扩展的机制在碳纤维类型之间看起来相似。