Department of Materials Science and Engineering, African University of Science and Technology, Nigeria; Department of Mechanical Engineering, Koforidua Technical University, Koforidua, Ghana.
Department of Materials Science and Engineering, African University of Science and Technology, Nigeria.
Acta Biomater. 2019 Oct 1;97:535-543. doi: 10.1016/j.actbio.2019.07.023. Epub 2019 Jul 13.
Turtle shells comprising of cortical and trabecular bones exhibit intriguing mechanical properties. In this work, compression tests were performed using specimens made from the carapace of Kinixys erosa turtle. A combination of imaging techniques and mechanical testing were employed to examine the responses of hierarchical microstructures of turtle shell under compression. Finite element models produced from microCT-scanned microstructures and analytical foam structure models were then used to elucidate local responses of trabecular bones deformed under compression. The results reveal the contributions from micro-strut bending and stress concentrations to the fractural mechanisms of trabecular bone structures. The porous structures of turtle shells could be an excellent prototype for the bioinspired design of deformation-resistant structures. STATEMENT OF SIGNIFICANCE: In this study, a combination of analytical, computational models and experiments is used to study the underlying mechanisms that contribute to the compressive deformation of a Kinixys erosa turtle shell between the nano-, micro- and macro-scales. The proposed work shows that the turtle shell structures can be analyzed as sandwich structures that have the capacity to concentrate deformation and stresses within the trabecular bones, which enables significant energy absorption during compressive deformation. Then, the trends in the deformation characteristics and the strengths of the trabecular bone segments are well predicted by the four-strut model, which captures the effects of variations in strut length, thickness and orientation that are related to microstructural uncertainties of the turtle shells. The above results also suggest that the model may be used to guide the bioinspired design of sandwich porous structures that mimic the properties of the cortical and trabecular bone segments of turtle shells under a range of loading conditions.
龟壳由皮质骨和小梁骨组成，具有有趣的力学性能。在这项工作中，使用来自 Kinixys erosa 龟的壳标本进行了压缩测试。结合成像技术和力学测试，研究了龟壳的分层微观结构在压缩下的响应。然后，使用从微 CT 扫描的微观结构生成的有限元模型和分析的泡沫结构模型来阐明在压缩下变形的小梁骨的局部响应。结果揭示了微结构弯曲和应力集中对小梁骨结构断裂机制的贡献。龟壳的多孔结构可以成为抗变形结构仿生设计的优秀原型。
在这项研究中，采用了分析、计算模型和实验相结合的方法，研究了导致 Kinixys erosa 龟壳在纳米、微米和宏观尺度之间压缩变形的潜在机制。提出的工作表明，龟壳结构可以分析为夹层结构，具有在小梁骨内集中变形和应力的能力，从而在压缩变形过程中吸收大量能量。然后，四支柱模型很好地预测了小梁骨段的变形特征和强度趋势，该模型捕捉到了与龟壳微观结构不确定性相关的支柱长度、厚度和方向变化的影响。上述结果还表明，该模型可用于指导仿生设计夹层多孔结构，模拟龟壳皮质骨和小梁骨段在一系列加载条件下的性能。
