Collaborative Research Strain-rate Dependent Properties of Cement-Based Materials: A Multi-Scale Experimental and Modeling Effort

本提案概述了一个联合实验和计算程序，旨在为水泥基材料的多尺度模型开发框架，这将为其非均质结构的定量描述提供进展，并能够预测加载率对从普通强度混凝土到纤维增强超高性能混凝土等材料失效的影响。具体而言，建议的活动分为四个任务：1)结构描述符的多尺度结构和中尺度波动的定量表征；2)建立预测混凝土/胶凝材料应变率相关行为的微观力学模型；3)基于随机模拟的混凝土/胶凝材料细观本构特性变化模型；4)试样在不同应变率下单轴/双轴压缩的全尺寸有限元模型，并使用Kolsky bar设备进行实验验证。通过提出的活动进行的研究将通过提供新的建模范式和实验技术来解决混凝土材料的冲击载荷的重要问题，以解决水泥基材料的应变率相关破坏问题。这些协议可以为提高材料的抗爆性能和更有效的结构设计奠定基础。此外，该技术还有望应用于高应变率下更广泛的脆性材料，例如采矿爆炸下岩石的破坏模型或弹道载荷下陶瓷装甲的破坏模型。拟议的活动代表了一种多机构合作，这将使由pi指导的学生不仅可以接触到pi的专业知识，还可以接触到每个相关机构的教育研究环境。每个PI将指导一名博士生和本科生研究人员，他们将被鼓励定期前往其他机构分享研究成果。

This proposal outlines a joint experimental and computational program aimed at developing the framework for a multi-scale model of cement-based materials, which will provide for advances in quantitative descriptions of their heterogenous structure and an ability to predict the effect of loading rate on failure in materials ranging from normal strength concrete to fiber-reinforced ultrahigh performance concrete. Specifically, the proposed activities are divided into four tasks: 1) quantitative characterization of multi-scale structure and meso-scale fluctuations in structural descriptors; 2) development of micromechanical models for predicting strain-rate dependent behavior of concrete/cementitious materials; 3) stochastic simulation-based modeling of variations in meso-scale constitutive properties of concrete/cementitious materials; and, 4) full-scale finite element model of samples under uniaxial/biaxial compression at varying strain rates, along with experimental validation using Kolsky bar equipment. The research conducted through the proposed activities will address the important problem of impact loading on concrete materials, by providing new modeling paradigms and experimental techniques to address the strain-rate-dependent failure of cement-based materials. These protocols can form the basis for improved blast-resistance of materials and more effective structural design. In addition, the techniques are also expected to be applicable to the broader family of brittle materials under high strain rates, such as modeling failure of rocks under mining blasts or ceramic armors under ballistic loading. The proposed activities represent a multi-institutional collaboration, which will provide students mentored by the PIs exposure not only to the expertise of both PIs, but also to the educational research environments at each of the involved institutions. Each PI will mentor one Ph.D. student and undergraduate researchers who will all be encouraged to travel to the other institution on a regular basis to share findings.