The mechanical properties of soft tissues are strongly dependent on their microstructures which evolve with aging and diseases. In this paper, a micromechanical model is presented to investigate the mechanical properties of tendons and ligaments, which are treated as planar crimped fiber-reinforced composites. The interaction among the constituents in such a composite is accounted for by utilizing the Mori–Tanaka method. Explicit analytical solutions are derived for describing the effects of microstructures on its macroscopic elastic properties, which are in good agreement with both finite element analysis and relevant experimental results. It is found that fiber waviness has a significant influence on the elastic properties of tendon and ligament. Our findings also demonstrate that planar crimp is significant to achieve the large Poisson's ratio of ligament and tendon, thereby revealing a novel structure–function mechanism. Parametric analysis further elucidates that their Poisson's ratios are also dependent on the volume fractions of crimped fibers and the elastic properties of the matrix. This work not only provides a theoretical method to predict the constitutive relation of biocomposites containing wavy fibers, but also expands our knowledge on the microstructural origin of large Poisson's ratios of soft tissues.

软组织的机械性能在很大程度上取决于其随着衰老和疾病而发展的微结构。在本文中，提出了一个微力学模型来研究肌腱和韧带的机械性能，这些肌腱和韧带被视为平面卷曲的纤维增强复合材料。这种复合材料中各成分之间的相互作用是通过使用Mori-Tanaka方法进行的。得出了明确的解析解来描述微观结构对其宏观弹性性能的影响，这与有限元分析和相关的实验结果都非常吻合。发现纤维波纹度对肌腱和韧带的弹性特性具有显着影响。我们的发现还表明，平面压接对于实现大型泊松效应具有重要意义。韧带和肌腱的比率，从而揭示了一种新颖的结构-功能机制。参数分析进一步阐明了它们的泊松比还取决于卷曲纤维的体积分数和基质的弹性。这项工作不仅为预测包含波浪纤维的生物复合材料的本构关系提供了一种理论方法，而且扩展了我们对大的软组织泊松比的微观结构起源的认识。