Kochetkova Tatiana, Peruzzi Cinzia, Braun Oliver, Overbeck Jan, Maurya Anjani K, Neels Antonia, Calame Michel, Michler Johann, Zysset Philippe, Schwiedrzik Jakob
Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials & Nanostructures, Thun, Switzerland.
Empa, Swiss Federal Laboratories for Materials Science and Technology, Transport at Nanoscale Interfaces Laboratory, Dübendorf, Switzerland; Department of Physics, University of Basel, Switzerland.
Acta Biomater. 2021 Jan 1;119:390-404. doi: 10.1016/j.actbio.2020.10.034. Epub 2020 Oct 26.
Bone is a natural composite possessing outstanding mechanical properties combined with a lightweight design. The key feature contributing to this unusual combination of properties is the bone hierarchical organization ranging from the nano- to the macro-scale. Bone anisotropic mechanical properties from two orthogonal planes (along and perpendicular to the main bone axis) have already been widely studied. In this work, we demonstrate the dependence of the microscale compressive mechanical properties on the angle between loading direction and the mineralized collagen fibril orientation in the range between 0° and 82°. For this, we calibrated polarized Raman spectroscopy for quantitative collagen fibril orientation determination and validated the method using widely used techniques (small angle X-ray scattering, micro-computed tomography). We then performed compression tests on bovine cortical bone micropillars with known mineralized collagen fibril angles. A strong dependence of the compressive micromechanical properties of bone on the fibril orientation was found with a high degree of anisotropy for both the elastic modulus (E/E=3.80) and the yield stress (σ/σ=2.54). Moreover, the post-yield behavior was found to depend on the MCF orientation with a transition between softening to hardening behavior at approximately 50°. The combination of methods described in this work allows to reliably determine structure-property relationships of bone at the microscale, which may be used as a measure of bone quality.
骨骼是一种天然复合材料，具有出色的机械性能和轻量化设计。促成这种非凡性能组合的关键特征是从纳米尺度到宏观尺度的骨骼层次结构。骨骼在两个正交平面（沿主骨轴方向和垂直于主骨轴方向）的各向异性机械性能已经得到了广泛研究。在这项工作中，我们展示了微观尺度压缩机械性能对加载方向与矿化胶原纤维取向之间夹角（0°至82°）的依赖性。为此，我们校准了偏振拉曼光谱以定量测定胶原纤维取向，并使用广泛使用的技术（小角X射线散射、微计算机断层扫描）验证了该方法。然后，我们对具有已知矿化胶原纤维夹角的牛皮质骨微柱进行了压缩测试。结果发现，骨骼的压缩微观机械性能强烈依赖于纤维取向，弹性模量（E/E = 3.80）和屈服应力（σ/σ = 2.54）均具有高度各向异性。此外，还发现屈服后行为取决于矿化胶原纤维取向，在大约50°时会从软化行为转变为硬化行为。这项工作中描述的方法组合能够可靠地确定微观尺度下骨骼的结构-性能关系，这可作为衡量骨骼质量的一个指标。
