基于内聚力模型的双网络水凝胶断裂特性的研究

Double-network hydrogels are promising in biomedicine and material engineering due to good biocompatibility, great flexibility and high toughness. However, theoretically, the fracture characteristics of double-network hydrogels are poorly understood and their major influence factors have not been fully revealed; and experimental phenomena such as crack blunting and delayed fracture have not been well explained. Therefore, in this project, based on cohesive zone models, the fracture characteristics of double-network hydrogels will be studied by employing fracture experiments, analytic analysis and finite element analysis. In fracture experiments, fracture toughness, crack opening profile, the size of damage zone near the crack tip will be tested. In analytic analysis, hyperelastic models will be employed to describe the large deformation behavior of double-network hydrogels; and the damage behavior will be defined by cohesive zone models. The explicit relation between fracture toughness and its main influence factors will be derived. In finite element analysis, the mechanical-chemical coupling effect will be considered; the fracture process of double-network hydrogels will be simulated; and the experimental phenomena such as crack blunting and delayed fracture will be explained. Finally, the fracture characteristics of double-network hydrogels will be revealed at macroscopic level. This work will provide a theoretical basis for the application and design of double-network hydrogels and soft biomaterials.

双网络水凝胶具有生物相容性好、柔度大、韧性高等优点，在生物医学、材料工程等领域有着广阔的应用前景。但是，目前双网络水凝胶的断裂特性及其关键影响因素还未探明，裂纹钝化、迟滞断裂等试验现象还未得到合理的理论解释。针对现有研究的不足，本项目将以内聚力模型为理论基础，从断裂试验、解析分析、有限元分析三方面对双网络水凝胶的断裂特性开展系统的研究。在试验中测试双网络水凝胶的断裂韧性、裂纹张开形态以及裂纹尖端损伤区大小；在解析分析中采用超弹性模型描述材料的大变形特征，应用内聚力模型描述裂纹尖端区域材料的损伤行为，建立材料断裂韧性与其关键影响因素之间的显式关系；在有限元分析中引入力学-化学耦合效应，模拟双网络水凝胶的断裂过程，解释试验中的裂纹钝化、迟滞断裂等物理现象。最终从理论上宏观地揭示双网络水凝胶的断裂特性，为双网络水凝胶及软生物材料的应用、开发、设计提供理论基础。

双网络水凝胶具有生物相容性好、柔度大、韧性高等优点，在生物医学、材料工程等领域有着广阔的应用前景。本项目应用解析方法，辅以试验、数值模拟验证，对双网络水凝胶的力学及断裂特性开展研究。面向双网络水凝胶等软材料，将传统的JKR模型扩展到薄膜的压痕问题中，得到了压痕力、压痕半径及压痕深度的显式表达式，提出了一种考虑粘附效应的、杨氏弹性模量的简便测量理论及实验方法。针对双网络水凝胶等材料在断裂过程中的大变形特征，应用两种超弹性模型求解了裂纹尖端的变形场、应力场，发现两种模型在裂纹尖端给出了不同的应力奇异性。揭示了裂纹扩展速度对应力场及其奇异性的影响，预测了裂纹的分叉速度及扩展路径，解释了实验现象。利用复变函数法，将内聚力模型扩展到超弹性材料损伤问题中，解析求解了一种超弹性平面中的I型裂纹尖端的内聚力区长度，及其影响因素，探求了损伤效应对裂纹扩展的作用机制，建立了材料断裂韧性与关键影响因素间的显式联系，宏观地揭示了材料的增韧机理。本项工作可为双网络水凝胶及软生物材料的应用、开发提供理论基础。