Polycarbonate polyurethane has cartilage-like, hygroscopic, and elastomeric properties that make it an attractive material for orthopedic joint replacement application. However, little data exists on the cyclic loading and fracture behavior of polycarbonate polyurethane. This study investigates the mechanisms of fatigue crack growth in polycarbonate polyurethane with respect to time dependent effects and conditioning. We studied two commercially available polycarbonate polyurethanes, Bionate® 75D and 80A. Tension testing was performed on specimens at variable time points after being removed from hydration and variable strain rates. Fatigue crack propagation characterized three aspects of loading. Study 1 investigated the impact of continuous loading (24 h/day) versus intermittent loading (8–10 h/day) allowing for relaxation overnight. Study 2 evaluated the effect of frequency and study 3 examined the impact of hydration on the fatigue crack propagation in polycarbonate polyurethane. Samples loaded intermittently failed instantaneously and prematurely upon reloading while samples loaded continuously sustained longer stable cracks. Crack growth for samples tested at 2 and 5 Hz was largely planar with little crack deflection. However, samples tested at 10 Hz showed high degrees of crack tip deflection and multiple crack fronts. Crack growth in hydrated samples proceeded with much greater ductile crack mouth opening displacement than dry samples. An understanding of the failure mechanisms of this polymer is important to assess the long-term structural integrity of this material for use in load-bearing orthopedic implant applications.

聚碳酸酯聚氨酯具有类软骨，吸湿和弹性的特性，使其成为骨科关节置换应用的有吸引力的材料。然而，关于聚碳酸酯聚氨酯的循环载荷和断裂行为的数据很少。这项研究调查了聚碳酸酯聚氨酯疲劳裂纹扩展的时间依赖性效应和调节机制。我们研究了两种商用聚碳酸酯聚氨酯，Bionate®75D和80A。从水化作用和变化的应变速率移除后，在不同的时间点对标本进行拉伸测试。疲劳裂纹扩展表征了载荷的三个方面。研究1研究了连续负荷（24 h /天）与间歇负荷（8-10 h /天）对放松过夜的影响。研究2评估了频率的影响，研究3检验了水合对聚碳酸酯聚氨酯中疲劳裂纹扩展的影响。重新加载时，间歇加载的样品会瞬间失效，而连续加载时会持续出现更长的稳定裂纹。在2和5 Hz下测试的样品的裂纹扩展在很大程度上是平面的，几乎没有裂纹挠度。但是，在10 Hz下测试的样品显示出很高的裂纹尖端偏斜度和多个裂纹前沿。在水合样品中的裂纹扩展比在干燥样品中的韧性裂纹口张开位移大得多。了解这种聚合物的失效机理对于评估该材料在承重骨科植入物中的长期结构完整性至关重要。