中高应变率下碳纳米管/碳纤维多尺度增强混凝土的动力特性及界面增强机制

With the rapid growth of China's economic strength, more and more large concrete structures are being launched one after another. In order to meet the requirements of anti-hurricane, anti-strong earthquake and anti-explosion performance, the concrete dynamic characteristics under medium-high strain rates need to be further improved. This project takes Carbon Nanotubes /Carbon Fibers Multiscale Reinforced Concrete (CTFRC) as the research object. It carries out basic scientific research on its preparation technology, dynamic characteristics and interface enhancement mechanism through experimental test, theoretical model and numerical simulation. The specific contents include: The key technology of CTFR dispersion in alkaline concrete environment was studied on the basis of preparing Carbon Nanotubes /Carbon Fibers Multiscale Reinforcement (CTFR) and corresponding dispersion, combined with microstructure test and static mechanical test. Based on the Sargin nonlinear elastic constitutive model and dynamic mechanical tests, the strength, deformation and shape parameters are introduced to construct the CTFRC dynamic constitutive model at medium and high strain rates. Based on the microstructure characteristics and nanomechanical properties, the molecular dynamics of simulating CTFRC micro-units are established. The model is used to analyze the mechanical behavior of microcells under shearing action, and the interface enhancement mechanism of CTFR is described from the nanoscale perspective. The results of this project can provide theoretical basis and technical support for CTFRC applications in civil and military fields.

随着我国经济实力快速增长，大型混凝土结构发展越来越快，为满足其抗飓风、抗强震和抗爆炸性能要求，需进一步提升混凝土在中高应变率下的动力特性。本项目以碳纳米管/碳纤维多尺度增强混凝土（CTFRC）为研究对象，通过试验测试、理论模型和数值模拟等手段，对其制备技术、动力特性和界面增强机制进行基础科学研究。具体内容包括：在制备碳纳米管/碳纤维多尺度增强体（CTFR）和相应分散液基础上，结合微观测试试验和静态力学试验，研究CTFR在碱性混凝土环境中有效分散的关键技术；以Sargin非线弹性本构为基础，基于动态力学试验，引入强度、变形和形状参数，构建中高应变率下CTFRC动态本构模型；基于微观结构特征和纳米力学性质，建立模拟含CTFRC微单元的分子动力学模型，分析微单元在剪切作用下的力学行为，从纳米尺度层面阐述CTFR的界面增强机制。本项目成果可为CTFRC在民用和军事领域的应用提供理论依据和技术支持。

本项目聚焦于强化混凝土结构抗震、防爆、耐冲击性能的工程背景，以5种碳纳米管-碳纤维多尺度增强体（Carbon nanotube - Carbon fiber multi-scale reinforcement, CTFR）体积掺量（0%、0.1%、0.2%、0.3%和0.4%）的碳纳米管-碳纤维多尺度增强混凝土（Carbon nanotube - Carbon fiber multi-scale reinforced concrete, CTFRC）为研究对象，采用试验测试、理论分析、模型构建和数值模拟相结合的研究手段，针对CTFR与CTFRC的制备技术以及CTFRC的力学特性、改性机理等展开了系统地研究。主要研究内容及关键成果包括：.（1）探索了CTFR及CTFRC的制备方法。首先，基于超声辅助电泳沉积技术，将碳纳米管（CNTs）接枝到碳纤维（CF）表面，制备出CTFR；其次，配制了CTFR-饱和氢氧化钙混合液，分析了CTFR在碱性环境中的分散情况；最后，综合考虑CTFR的分散稳定性以及各种原材料的基本特性，优化了纤维混凝土的浇筑工艺，制备了不同CTFR掺量的CTFRC试件。.（2）明确了CTFRC静、动态力学性能的演化特点。首先，开展了CTFRC的静力试验，研究了CTFR掺量对混凝土静力特性的影响规律；其次，进行了CTFRC的动力试验，探讨了其动力指标随应变率的变化关系；最后，构建了CTFRC的动态受压本构模型。结果表明：CTFRC具有优异的准静态力学性能和抗冲击性能，模型计算曲线与实测数据之间的吻合程度较高。.（3）揭示了CTFR对混凝土材料的增效机制。首先，分析了CTFR对混凝土内部裂缝及孔隙的改善作用；其次，采用纳米压痕技术，研究了CTFRC微观弹性模量的变化规律；最后，建立了CTFRC的分子动力学模型，从纳米尺度分析其改性机理。结果表明：CTFR有助于优化复合材料的基体结构，强化纤维与基体的界面结合，促进混凝土力学性能的提升。.相关研究成果既能够为混凝土材料的力学性能改良设计提供科学依据，还可以为CTFRC在军事及民用设施中的实际推广应用奠定理论和技术基础，具有重要的科研价值与工程意义。