A natural energy absorbent polymer composite: The equine hoof wall

被引:51
|
作者
Huang, Wei [1 ]
Yaraghi, Nicholas A. [2 ]
Yang, Wen [1 ]
Velazquez-Olivera, Alexis [3 ]
Li, Zezhou [1 ]
Ritchie, Robert O. [4 ]
Kisailus, David [2 ,5 ]
Stover, Susan M. [6 ]
McKittrick, Joanna [1 ,3 ]
机构
[1] Univ Calif San Diego, Mat Sci & Engn Program, La Jolla, CA 92093 USA
[2] Univ Calif Riverside, Mat Sci & Engn Program, Riverside, CA 92521 USA
[3] Univ Calif San Diego, Dept Mech & Aerosp Engn, La Jolla, CA 92093 USA
[4] Univ Calif Berkeley, Dept Mat Sci & Engn, Berkeley, CA 94720 USA
[5] Univ Calif Riverside, Dept Chem & Environm Engn, Riverside, CA 92521 USA
[6] Univ Calif Davis, Sch Vet Med, Davis, CA 95616 USA
基金
美国国家科学基金会;
关键词
Equine hoof; Keratin; Energy absorption; Tubular structure; Mechanical properties; SHEEP OVIS-CANADENSIS; MECHANICAL-PROPERTIES; KERATIN; DESIGN; HAIR; FRACTURE; MODULUS; MODEL; INDENTATION; MODULATION;
D O I
10.1016/j.actbio.2019.04.003
中图分类号
R318 [生物医学工程];
学科分类号
0831 ;
摘要
The equine hoof has been considered as an efficient energy absorption layer that protects the skeletal elements from impact when galloping. In the present study, the hierarchical structure of a fresh equine hoof wall and the energy absorption mechanisms are investigated. Tubules are found embedded in the inter tubular matrix forming the hoof wall at the microscale. Both tubules and intertubular areas consist of keratin cells, in which keratin crystalline intermediate filaments (IFs) and amorphous keratin fill the cytoskeletons. Cell sizes, shapes and IF fractions are different between tubular and intertubular regions. The structural differences between tubular and intertubular areas are correlated to the mechanical behavior of this material tested in dry, fresh and fully hydrated conditions. The stiffness and hardness in the tubule areas are higher than that in the intertubular areas in the dry and fresh samples when loaded along the hoof wall; however, once the samples are fully hydrated, the intertubular areas become stiffer than the tubular areas due to higher water absorption in these regions. The compression behavior of hoof in different loading speed and directions are also examined, with the isotropy and strain-rate dependence of mechanical properties documented. In the hoof walls, mechanistically the tubules serve as a reinforcement, which act to support the entire wall and prevent catastrophic failure under compression and impact loading. Elastic buckling and cracking of the tubules are observed after compression along the hoof wall, and no shear-banding or severe cracks are found in the intertubular areas even after 60% compression, indicating the highly efficient energy absorption properties, without failure, of the hoof wall structure. Statement of Significance The equine hoof wall is found to be an efficient energy absorbent natural polymer composite. Previous studies showed the microstructure and mechanical properties of the hoof wall in some perspective. However, the hierarchical structure of equine hoof wall from nano- to macro-scale as well as the energy absorption mechanisms at different strain rates and loading orientations remains unclear. The current study provides a thorough characterization of the hierarchical structure as well as the correlation between structure and mechanical behaviors. Energy dissipation mechanisms are also identified. The findings in the current research could provide inspirations on the designs of impact resistant and energy absorbent materials. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
引用
收藏
页码:267 / 277
页数:11
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