基于细观结构的建筑用织物类膜材平面应力下中心裂缝破坏机理研究

With the increased emphasis on the safety of membrane structures, study on actual crack tearing characteristics of woven fabric composites loaded in situ becomes a current research hotspot. As the biaxial tearing tests allow an adequate investigation of the crack propagation in the presence of a biaxial stress state, this proposal investigates the central crack tearing mechanism of the architectural fabrics affected by their internal and external factors, using the nonlinear binary modeling technique and the biaxial testing method. The following work will be conducted carefully: ① Considering the meso- structure features of the studied materials, nonlinear binary models (NBM) are established to reveal the central tearing mechanism of architectural fabrics influenced by different weave structures of yarns, nonlinearity of constituent materials, void defects scattered randomly throughout the coatings or functional layers, and the irregular yarn waviness. ② Biaxial tearing tests and binary models are carefully conducted on specimens, and the influences of biaxial tensile stress or shear stress levels, stress ratios, and crack parameters on the tearing behaviors of architectural fabrics are discussed. ③ Based on the NBM analysis, dimensions of cruciform specimens for central tearing analysis are optimized, and numbers of models are studied to revise and improve the testing standard of biaxial tearing properties for architectural fabrics. In addition, the stress reduction factor of tearing resistance, the critical crack length for a certain stress state, and reinforcing methods of architectural fabrics with a central crack are also investigated carefully. The work will benefit the improvement of theory of fracture mechanics to analyze the central crack propagation and tearing resistance for woven fabric composites. What’s more, the research finds will provide a scientific foundation for the rational design of architectural fabrics with high tearing resistance, and for the safety assessment of the membrane structures.

随着对膜结构安全的日益重视，实际受荷状态下织物类膜材的裂缝破坏问题成为近年研究热点。本项目针对可模拟双向受力状态下裂缝破坏的中心撕裂形式，采用非线性双组元力学模型和双向试验技术，研究建筑用织物类膜材中心裂缝破坏性能受内外因素的影响机理。主要内容包括：① 基于膜材的细观结构建立非线性双组元力学模型，探究裂缝破坏行为受纱线编织构造、组分材料非线性、涂层/功能层随机微缺陷及纱线不规则取向的影响机理；② 基于双向撕裂试验技术和双组元力学模型，研究双向拉伸、剪切应力水平、应力比例及裂缝参数对膜材撕裂力学性能的影响规律；③ 利用双组元力学模型，优化膜材中心裂缝试样尺寸，完善膜材双向中心撕裂试验标准，并进行含裂缝膜材的损伤容限分析及修复措施探索。研究工作将揭示织物类膜材中心裂缝扩展机理、完善其双向撕裂强度理论，从而为建筑用织物类膜材抗撕裂力学性能的优化设计及膜结构的安全性评估提供科学依据。

膜结构是一种新型大跨空间结构形式，随着对膜结构安全的日益重视，实际受荷状态下织物类膜材的裂缝破坏问题成为近年研究热点。作为现代膜结构的主体材料，柔性织物类膜材撕裂力学性能对整体结构安全性至关重要。织物膜面处于双向受力状态下，拉剪力学性能是进行裂纹破坏强度及破坏机理的分析基础；本研究首先在材料面内拉伸及剪切力学性能方面，进行系列单、双轴拉伸、偏轴拉伸及双向剪切等试验，配合DIC非接触摄影测量技术，深入研究了织物材料拉伸变形非线性、断裂强度、拉剪刚度、全域泊松比响应规律、以及相关强度准则、刚度和泊松比参数预测理论。然后，基于测试标准FAA-P-8110，配合FEA细观结构数值模型及理论机理分析，对织物材料的单轴撕裂破坏性质、撕裂强度规律、裂纹扩展特征、以及撕裂强度理论和裂纹扩展机制进行了深入研究；最后，基于双向薄膜试验系统及细观有限元数值模型，进行了双轴中心切缝撕裂试验及数值模型研究，研究了双向拉伸、剪切应力水平、应力比例、裂缝参数、以及细观结构、纱线力学性能和纬斜不规则等内外因素对裂缝扩展及撕裂抗力的影响规律。研究表明，膜材拉剪性能及力学参数受拉剪应力状态、应力比例及材料类型影响显著，表现出显著拉剪耦合、正交异性及非线性特征；膜材的偏轴抗拉及撕裂强度遵守新的“W”型准则，异于传统强度的“U”型准则。织物材料的撕裂抗力与裂纹延展与组分材料的力学参数、纱线编织密度、弓曲率（内因）及张力水平、应力比例、剪切应力状态、裂缝倾角及裂缝长度等（外因）有关。裂纹破坏机制是膜材材料性质、损伤参数及面内拉剪应力状态共同决定。研究所得结论及成果可为高性能织物类膜材的设计及现代膜结构的受力合理性及安全性评估提供参考。