Mineralized collagen fibrils (MCFs) are important building blocks of bone at the submicroscale, and the mechanical performance of MCF arrays has a great influence on fracture resistance of bone at large length scales. In this study, we carry out the analyses of fracture process in MCF arrays under tensile loading. The plastic deformation of extrafibrillar matrix (EFM), post-yield behavior of MCFs, MCF breakage and debonding of the MCF-EFM interface are accounted for in the calculations. It is found that the fracture mechanisms of MCF arrays depend on the post-yield characteristics of MCFs. Shear-band-induced cracking of MCFs is the dominant fracture mechanism in the case of strain softening of MCFs, while strain hardening of MCFs promotes the MCF-EFM interfacial debonding, which controls fracture of MCF arrays. In addition, we reveal that plastic energy dissipation of MCFs and EFM provides major contribution to toughness of MCF arrays. Compared with the case of strain softening of MCFs, the MCFs exhibiting post-yield strain hardening can give rise to larger plastic deformation zone in MCFs and activate higher levels of plastic strain of EFM, enhancing plastic energy dissipation and thereby amplifying toughness of MCF arrays. The findings of this study shed new light on the fracture mechanisms of bone associated with alterations in submicroscale structure and composition.

矿化胶原纤维（MCF）是亚微米尺度骨的重要组成部分，MCF阵列的机械性能对大长度尺度骨的抗断裂性有很大影响。在本研究中，我们对 MCF 阵列在拉伸载荷下的断裂过程进行了分析。计算中考虑了原纤维外基质 (EFM) 的塑性变形、MCF 的屈服后行为、MCF 断裂和 MCF-EFM 界面脱粘。研究发现，MCF 阵列的断裂机制取决于 MCF 的屈服后特性。在MCF应变软化的情况下，MCF的剪切带诱导开裂是主要的断裂机制，而MCF的应变硬化促进MCF-EFM界面脱粘，从而控制MCF阵列的断裂。此外，我们发现 MCF 和 EFM 的塑性能量耗散对 MCF 阵列的韧性做出了重大贡献。与MCF应变软化的情况相比，表现出屈服后应变硬化的MCF可以在MCF中产生更大的塑性变形区，并激活更高水平的EFM塑性应变，增强塑性能量耗散，从而增强MCF阵列的韧性。这项研究的结果为与亚微米结构和成分变化相关的骨骨折机制提供了新的线索。增强塑性能量耗散，从而增强 MCF 阵列的韧性。这项研究的结果为与亚微米结构和成分变化相关的骨骨折机制提供了新的线索。增强塑性能量耗散，从而增强 MCF 阵列的韧性。这项研究的结果为与亚微米结构和成分变化相关的骨骨折机制提供了新的线索。