Aldegaither Nouf, Sernicola Giorgio, Mesgarnejad Ataollah, Karma Alain, Balint Daniel, Wang Jianglong, Saiz Eduardo, Shefelbine Sandra J, Porter Alexandra E, Giuliani Finn
Department of Materials Science & Engineering, Imperial College London, Kensington, London, SW7 2AZ, UK; College of Science and Health Professions, King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia.
Department of Materials Science & Engineering, Imperial College London, Kensington, London, SW7 2AZ, UK.
Acta Biomater. 2021 Feb;121:475-483. doi: 10.1016/j.actbio.2020.12.007. Epub 2020 Dec 9.
Bone's hierarchical arrangement of collagen and mineral generates a confluence of toughening mechanisms acting at every length scale from the molecular to the macroscopic level. Molecular defects, disease, and age alter bone structure at different levels and diminish its fracture resistance. However, the inability to isolate and quantify the influence of specific features hampers our understanding and the development of new therapies. Here, we combine in situ micromechanical testing, transmission electron microscopy and phase-field modelling to quantify intrinsic deformation and toughening at the fibrillar level and unveil the critical role of fibril orientation on crack deflection. At this level dry bone is highly anisotropic, with fracture energies ranging between 5 and 30 J/m depending on the direction of crack propagation. These values are lower than previously calculated for dehydrated samples from large-scale tests. However, they still suggest a significant amount of energy dissipation. This approach provides a new tool to uncouple and quantify, from the bottom up, the roles played by the structural features and constituents of bone on fracture and how can they be affected by different pathologies. The methodology can be extended to support the rational development of new structural composites.
骨骼中胶原蛋白和矿物质的分层排列产生了一系列增韧机制，这些机制在从分子到宏观的各个长度尺度上发挥作用。分子缺陷、疾病和年龄会在不同层面改变骨骼结构，并降低其抗骨折能力。然而，由于无法分离和量化特定特征的影响，我们对其理解以及新疗法的开发都受到了阻碍。在此，我们结合原位微机械测试、透射电子显微镜和相场建模，以量化纤维水平的内在变形和增韧，并揭示纤维取向对裂纹偏转的关键作用。在这个层面上，干燥骨骼具有高度各向异性，根据裂纹扩展方向的不同，断裂能在5到30焦耳/平方米之间。这些值低于之前从大规模测试中计算出的脱水样品的值。然而，它们仍然表明存在大量的能量耗散。这种方法提供了一种新工具，可从下而上地分离和量化骨骼的结构特征和成分在骨折中所起的作用，以及它们如何受到不同病理状况的影响。该方法可扩展用于支持新型结构复合材料的合理开发。
