Yu Yang, Yang Wen, Wang Bin, Meyers Marc André
Department of NanoEngineering, University of California, San Diego, La Jolla, CA 92093, United States.
Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA 92093, United States; Department of Materials, Eidgenössische Technische Hochschule Zürich, Zürich 8093, Switzerland.
Mater Sci Eng C Mater Biol Appl. 2017 Apr 1;73:152-163. doi: 10.1016/j.msec.2016.12.008. Epub 2016 Dec 9.
The understanding of the mechanical behavior of hair under various conditions broadens our knowledge in biological materials science and contributes to the cosmetic industry. The hierarchical organization of hair is studied from the intermediate filament to the structural levels. The effects of strain rate, relative humidity, and temperature are evaluated. Hair exhibits a high tensile strength, 150-270MPa, which is significantly dependent on strain rate and humidity. The strain-rate sensitivity, approximately 0.06-0.1, is comparable to that of other keratinous materials and common synthetic polymers. The structures of the internal cortex and surface cuticle are affected by the large tensile extension. One distinguishing feature, the unwinding of the α-helix and the possible transformation to β-sheet structure of keratin under tension, which affects the ductility of hair, is analytically evaluated and incorporated into a constitutive equation. A good agreement with the experimental results is obtained. This model elucidates the tensile response of the α-keratin fibers. The contributions of elastic and plastic strains on reloading are evaluated and correlated to structural changes.
对头发在各种条件下力学行为的理解拓宽了我们在生物材料科学方面的知识，并为化妆品行业做出了贡献。从中间丝到结构层次对头发的层次结构进行了研究。评估了应变速率、相对湿度和温度的影响。头发具有较高的拉伸强度，为150 - 270MPa，这显著取决于应变速率和湿度。应变速率敏感性约为0.06 - 0.1，与其他角蛋白材料和常见合成聚合物相当。内部皮质和表面角质层的结构受到大拉伸延伸的影响。一个显著特征，即α - 螺旋的展开以及拉伸时角蛋白可能向β - 片层结构的转变，这影响了头发的延展性，经过分析评估并纳入本构方程。与实验结果取得了良好的一致性。该模型阐明了α - 角蛋白纤维的拉伸响应。评估了弹性和塑性应变对再加载的贡献，并将其与结构变化相关联。
