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

这项建议概述了一个联合实验和计算计划，旨在开发一个多尺度水泥基材料模型的框架，这将为水泥基材料的异质结构的定量描述提供进展，并能够预测从普通强度混凝土到纤维增强超高性能混凝土等材料中加载速度对破坏的影响。具体地说，拟议的活动分为四项任务：1)结构描述符中多尺度结构和细观尺度波动的定量表征；2)建立混凝土/胶凝材料的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/胶凝材料细观本构关系的建模；以及4)不同应变率下单轴/双轴压缩试件的全尺寸有限元模型，并使用Kolsky bar设备进行实验验证。通过拟议的活动进行的研究将通过提供新的建模范例和实验技术来解决混凝土材料上的冲击载荷这一重要问题，以解决水泥基材料的应变率相关失效问题。这些方案可以为提高材料的抗爆性和更有效的结构设计奠定基础。此外，预计这些技术还将适用于更广泛的高应变率下的脆性材料，例如在采矿爆炸下的岩石破坏模型或在弹道载荷下的陶瓷盔甲。拟议的活动代表了多机构合作，这将使由私人投资机构指导的学生不仅接触到两个私人投资机构的专业知识，而且还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，他们都将被鼓励定期前往另一所机构分享研究成果。

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.