Enhancement of fatigue resistance of strain-hardening cement-based composites by means of experimental-virtual multiscale material design

通过实验虚拟多尺度材料设计增强应变硬化水泥基复合材料的抗疲劳性能

• 批准号: 352324592
• 负责人: Professor Dr.-Ing. Michael Kaliske
• 金额: --
• 依托单位: Institut für Statik und Dynamik der Tragwerke
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/352324592?language=en
• 关键词: Enhancement; fatigue; resistance; strain; hardening

A new promising type of fiber-reinforced concrete – highly ductile concrete made by short fibers (Strain-Hardening Cement-based Composite, SHCC) – exhibits high deformation capacity at monotonic tensile loading. Its ductility results from progressive multiple cracking, which is accompanied by distinct strain hardening. To ensure safety and efficiency of building components of SHCC subject to cyclic loads, which are common in practical applications, profound knowledge of the fatigue behavior of this material and theoretical-numerical models are indispensable. The main question with respect to practical applications and to the purposeful improvement of the new fiber-reinforced concrete is: To what extent does the material in the cracked state lose its inherent ductility and tensile strength due to fatigue and how can these losses be mitigated by a goal-oriented material design?The complex behavior of SHCC under cyclic loading has been investigated in the first project phase at micro- and meso-levels. In particular, the degradation mechanisms of polymer microfibers, such as fiber fatigue, defibrillation and fiber squeezing, as well as the fiber-matrix bond properties were comprehensively studied. All microstructural constituents and their behaviors were described using numerical models.In the second phase of the project, experiments on the fatigue behavior of SHCC of different composition shall be performed predominantly on the macroscopic level by applying various loading scenarios and temperature. For a better understanding of the damage processes, the experiments shall be accompanied by detailed morphological investigations. The aim of this project phase is to combine the macroscopic behavior of SHCC under highly cyclic loading including the expected anisotropic material degradation with the damage mechanisms detected and described at the micro- and meso-level. The scale coupling of the numerical models for the meso- and macro-scale requires the development of a thermo-dynamically consistent homogenization for the stress and strain measures, as well as the internal material variables. To achieve a high compu-tational efficiency, time homogenization and adaptive discretization methods at high-performance computers are used.At the end of the project, there will be a comprehensive understanding of the damage mechanisms at different levels of observation, a coherent material characterization methodology, and a digital computational tool to predict and optimize the mechanical behavior of SHCC under cyclic loading. In addition to the SHCC material design, the virtual tool should also enable the targeted development of other types of fiber reinforced concrete for different loading scenarios (digitally enabled material design).

一种新型的有前途的纤维增强混凝土-由短纤维制成的高韧性混凝土（应变硬化水泥基复合材料，SHCC）-在单调拉伸载荷下表现出高变形能力。它的延展性是由渐进的多裂纹引起的，并伴随着明显的应变硬化。为了确保SHCC建筑构件在实际应用中常见的循环荷载作用下的安全性和有效性，必须深入了解这种材料的疲劳行为并建立理论-数值模型。关于实际应用和有目的地改进新型纤维增强混凝土的主要问题是：在何种程度上，材料在开裂状态下会因疲劳而失去其固有的延展性和抗拉强度，以及如何通过目标导向的材料设计来减轻这些损失？在第一个项目阶段，在微观和细观水平上研究了SHCC在循环荷载下的复杂行为。特别是对聚合物微纤维的疲劳、原纤化和挤压等降解机理以及纤维与基体的粘结性能进行了全面的研究。在本项目的第二阶段，将主要在宏观水平上通过施加不同的载荷方案和温度来进行不同成分的SHCC的疲劳行为的实验。为了更好地理解损伤过程，实验应伴随详细的形态学研究。该项目阶段的目的是将SHCC在高循环荷载下的宏观行为（包括预期的各向异性材料退化）与在微观和细观水平上检测和描述的损伤机制相结合。中尺度和宏观尺度的数值模型的尺度耦合需要开发一个热动力学一致的均匀化的应力和应变的措施，以及内部的材料变量。为了实现高计算效率，在高性能计算机上使用时间均匀化和自适应离散化方法。在项目结束时，将全面了解不同观测水平下的损伤机制，连贯的材料表征方法，以及预测和优化SHCC在循环载荷下的力学行为的数字计算工具。除了SHCC材料设计之外，虚拟工具还应该能够针对不同的加载场景（数字化材料设计）有针对性地开发其他类型的纤维增强混凝土。