基于微观力学模型的超高韧性水泥基复合材料动态拉伸力学行为与延性设计研究

混凝土的脆性易裂特征会造成防护结构背部大面积震塌，因此使用拉伸性能更为优异的新型混凝土对防护工程而言具有重要意义。超高韧性水泥基复合材料（简称UHTCC）是一种拉伸应变达3%以上的高韧性混凝土，目前该材料的动态拉伸力学性能的研究较少，相关的率效应机理仍不清晰。申请者的前期研究初步表明UHTCC的宏观动态拉伸力学性能与其内部纤维、基体以及界面的微观力学参数有关。本项目拟通过动态微观纤维拉拔试验建立UHTCC的各项微观力学参数与应变率的定量关系，在此基础上改进现有的微观理论设计模型，以指导动态荷载下UHTCC延性行为的设计。研究拟开展不同应变率下的UHTCC动态直接拉伸试验、缺口敏感性试验以及水和应变率耦合下的动态直接拉伸试验，建立UHTCC动态拉伸本构关系，揭示宏观应变率效应背后所蕴含的动态微观机理，为UHTCC在防护工程中的应用提供理论和技术支持。

A large spalling always occur on the back area of protective structures because of the brittleness of normal concrete, which result in the requirement of high performance concrete with superior tensile property to be used in these structures. Ultra high toughness cementitious composite (UHTCC) is a kind of high ductile concrete with tensile strain capacity more than 3%. However, the dynamic tensile mechanical properties of UHTCC are rarely studied at present, and the related mechanism underlying the strain rate sensitivity is still unclear. Based on the previous studies, the applicant proposed that the dynamic tensile property of UHTCC is related with the microscopic mechanical parameters in the fiber, matrix and their interface. The dynamic tension test on individual fibers and single fiber pull-out tests are performed in this project to establish the quantitative relationships between various microscopic mechanical parameters in UHTCC and the strain rate. Based on these, the existed design theory of UHTCC can be modified to account for the strain rate to predict the ductility behavior of UHTCC under the dynamic loading. Meanwhile, this project aim to conduct the dynamic direct tensile test, the notch sensitivity test and the wet/dry dynamic direct tensile test of UHTCC. Based on the experimental results, the dynamic tensile constitutive relationship of UHTCC can be established and the mechanism underlying the macroscopic strain rate sensitivity of UHTCC is revealed. This project can provide theoretical and technical support for the widely application of UHTCC in protective engineering.