Many biological materials contain nanofibers of helical shape to achieve multiple biological functions and superior mechanical properties. In this paper, we establish a microstructure-based crack-bridging model to investigate how the chiral morphologies of nanofibers contribute to the fracture properties of these natural nanocomposites. By using a cohesive interfacial model, the force–displacement relation for a helical nanofiber during pullout is first derived. It is found that the fracture toughness of biological materials is sensitive to the chiral morphology of fibers, suggesting a strategy to attain superior strength, toughness and elasticity. We discover an optimum helical angle that maximizes the toughness. A scaling law is provided to predict the macroscopic fracture toughness of helical fiber-reinforced nanocomposites in terms of microscopic geometric and mechanical parameters. This work not only sheds light on the toughening mechanisms of biological materials but also offers inspirations for design and optimization of advanced composites.

许多生物材料都包含螺旋形纳米纤维，以实现多种生物功能和卓越的机械性能。在本文中，我们建立了基于微结构的裂纹桥接模型，以研究纳米纤维的手性形态如何促进这些天然纳米复合材料的断裂性能。通过使用内聚界面模型，首先得出了螺旋纳米纤维在拉拔过程中的力-位移关系。已经发现，生物材料的断裂韧性对纤维的手性形态敏感，表明了获得优异的强度，韧性和弹性的策略。我们发现了使韧性最大化的最佳螺旋角。提供了定标定律，以从微观几何和机械参数方面预测螺旋纤维增强纳米复合材料的宏观断裂韧性。这项工作不仅阐明了生物材料的增韧机理，而且还为高级复合材料的设计和优化提供了灵感。