Arevalo Sofia E, Pruitt Lisa A
Department of Mechanical Engineering, University of California, Berkeley, CA, USA.
Department of Mechanical Engineering, University of California, Berkeley, CA, USA.
J Mech Behav Biomed Mater. 2020 Nov;111:104008. doi: 10.1016/j.jmbbm.2020.104008. Epub 2020 Jul 26.
Polyether ether ketone (PEEK) and PEEK composites are viable candidates for orthopedic implants owing to their ability for modulus match of surrounding bone tissue. The structural properties of these systems for load-bearing application in the body can be tailored by incorporating carbon fibers; to this end, polyacrylonitrile (PAN) and pitch fibers are commonly incorporated in the PEEK matrix. Mechanical property optimization for a given medical application requires consideration of carbon fiber type and volume fraction, as well as processing conditions for the composite systems. While much is known about the bulk mechanical properties of PEEK and PEEK composites, little is known about the nanomechanical properties of these systems. Insight into nanoscale behavior can offer valuable information about fiber-matrix interactions that may influence long-term integrity of these biomaterials when used in load bearing medical device applications. In this study, we utilize nanoindentation as a method to characterize mechanical behavior of clinical grade PEEK and PEEK composites. We examine PEEK formulations with pitch and PAN fibers and evaluate a range of thermal treatments known to influence polymer microstructure. We use a conospherical tip of 1.5 μm in radius and a conospherical tip of 20 μm radius to determine indentation modulus over different length scales. We correlate these findings with previous characterization on these same PEEK systems using microindentation. A novelty of this work is that we combine nanoindentation with k-means clustering to quantitatively discern the influence of heat treatment and carbon fiber type on the mechanical behavior of PEEK composites and their constituents. We demonstrate that nanoindentation is an effective characterization tool for discerning fiber-matrix interactions and measuring the mechanical behavior in response to thermal treatment and carbon fiber type in PEEK composites. Nanoindentation is shown to be a viable tool for characterizing complex biomaterials and can serve as an effective technique to guide optimization of microstructures for long-term structural applications in the body.
聚醚醚酮（PEEK）及其复合材料因其能够与周围骨组织实现模量匹配，是骨科植入物的可行候选材料。通过加入碳纤维，可以调整这些体系在人体承重应用中的结构性能；为此，通常将聚丙烯腈（PAN）纤维和沥青纤维加入到PEEK基体中。对于特定的医学应用，机械性能的优化需要考虑碳纤维类型、体积分数以及复合材料体系的加工条件。虽然人们对PEEK及其复合材料的整体力学性能了解很多，但对这些体系的纳米力学性能却知之甚少。深入了解纳米尺度行为可以提供有关纤维 - 基体相互作用的有价值信息，这些相互作用可能会影响这些生物材料在承重医疗设备应用中的长期完整性。在本研究中，我们利用纳米压痕法来表征临床级PEEK及其复合材料的力学行为。我们研究了含有沥青纤维和PAN纤维的PEEK配方，并评估了一系列已知会影响聚合物微观结构的热处理方法。我们使用半径为1.5μm的锥形球头和半径为20μm的锥形球头来确定不同长度尺度下的压痕模量。我们将这些结果与之前使用微压痕对这些相同PEEK体系进行的表征相关联。这项工作的新颖之处在于，我们将纳米压痕与k均值聚类相结合，以定量识别热处理和碳纤维类型对PEEK复合材料及其组分力学行为的影响。我们证明，纳米压痕是一种有效的表征工具，可用于识别纤维 - 基体相互作用，并测量PEEK复合材料中热处理和碳纤维类型对力学行为的影响。纳米压痕被证明是表征复杂生物材料的可行工具，并且可以作为一种有效技术来指导微观结构的优化，以用于人体的长期结构应用。
