In many fiber-reinforced tissues, collagen fibers are embedded within a glycosaminoglycan-rich extrafibrillar matrix. Knowledge of the structure–function relationship between the sub-tissue properties and bulk tissue mechanics is important for understanding tissue failure mechanics and developing biological repair strategies. Difficulties in directly measuring sub-tissue properties led to a growing interest in employing finite element modeling approaches. However, most models are homogeneous and are therefore not sufficient for investigating multiscale tissue mechanics, such as stress distributions between sub-tissue structures. To address this limitation, we developed a structure-based model informed by the native annulus fibrosus structure, where fibers and the matrix were described as distinct materials occupying separate volumes. A multiscale framework was applied such that the model was calibrated at the sub-tissue scale using single-lamellar uniaxial mechanical test data, while validated at the bulk scale by predicting tissue multiaxial mechanics for uniaxial tension, biaxial tension, and simple shear (13 cases). Structure-based model validation results were compared to experimental observations and homogeneous models. While homogeneous models only accurately predicted bulk tissue mechanics for one case, structure-based models accurately predicted bulk tissue mechanics for 12 of 13 cases, demonstrating accuracy and robustness. Additionally, six of eight structure-based model parameters were directly linked to tissue physical properties, further broadening its future applicability. In conclusion, the structure-based model provides a powerful multiscale modeling approach for simultaneously investigating the structure–function relationship at the sub-tissue and bulk tissue scale, which is important for studying multiscale tissue mechanics with degeneration, disease, or injury.

中文翻译：

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纤维增强组织的多尺度复合模型，可直接表示亚组织特性。

在许多纤维增强的组织中，胶原蛋白纤维嵌入富含糖胺聚糖的原纤维外基质中。了解亚组织特性和整体组织力学之间的结构-功能关系对于理解组织衰竭力学和制定生物修复策略非常重要。直接测量亚组织特性的困难导致人们对采用有限元建模方法的兴趣日益浓厚。但是，大多数模型是同质的，因此不足以研究多尺度组织力学，例如子组织结构之间的应力分布。为了解决这个限制，我们开发了一个基于结构的模型，该模型以天然纤维环结构为基础，其中纤维和基质被描述为占据不同体积的不同材料。应用了多尺度框架，使用单层单轴机械测试数据在亚组织规模上对模型进行了校准，同时通过预测组织多轴力学的单轴张力，双轴张力和简单剪切在大尺度上对模型进行了验证（13例） ）。将基于结构的模型验证结果与实验观察结果和同类模型进行比较。同类模型仅能准确预测一种情况下的大块组织力学，而基于结构的模型能准确预测13种情况中的12种的大块组织力学，证明了准确性和鲁棒性。此外，八个基于结构的模型参数中的六个直接与组织物理特性相关联，从而进一步扩展了其未来的适用性。结论，