ECC-Design_Approach-中文.ppt

ECC Design Approach Southeast University, Nanjing, China May, 2006 Victor Li E. Benjamin Wylie Collegiate Chair Professor of Civil and Environmental Engineering Professor of Materials Science and Engineering University of Michigan, Ann Arbor, MI 48105 USA Presentation Outline 报告提纲 ECC Micromechanics 细观力学 Fiber/Matrix Interface Tailoring 纤维/基体界面设计 Matrix Tailoring 基体设计 Theory Verifications 理论验证 Engineered Cementitious Composites工程水泥基复合材料 What is ECC? 什么是ECC A class of HPFRCC 一种高性能纤维增强水泥基复合材料 Strain-hardening 应变硬化 Low fiber content 低纤维含量 Micromechanics based design 基于细观力学设计 Overall Design Scheme 设计框架 Composite Design Approach 复合设计方法 – Flat Crack Propagation 平直裂缝的扩展 Micromechanics Based Design for Flat Crack Propagation 基于细观力学设计的平直裂缝扩展 Bridging Fibers as Non-linear Springs非线性弹簧－桥接纤维 Steady State Cracking Analyses 稳态开裂分析 Energy Balance Interpretation 能量平衡解析 Condition for Strain-Hardening 应变硬化条件 Micromechanical Model for sB-d Curve细观力学模型 Model Predict Micromechanics Design Strategy (for fiber and interface) Control “spring” behavior to achieve 控制弹簧行为获得Max C = f (Vf; fiber properties; interface properties) Critical fiber volume to convert FRC – ECC 控制临界纤维体积率使FRC转变为ECC Interface Design 界面设计 Tailoring: Surface Coating Control of Interface Properties 表面涂覆控制界面性能 Result: Strain Capacity Increases with Surface Coating Control 表面涂覆后应变能力增加 Surface Coating Effect on Fiber Damage 表面涂覆对纤维损伤的影响 Composite Design Approach 复合设计方法 – Microcrack Initiation 微裂纹引发 Matrix Tailoring 基体设计 Variation of Tensile Behavior 拉伸行为的变化 Cracking Strength and Flaw Size 开裂强度和缺陷尺寸 Tailoring of Flaw Size Distribution for Saturated Multiple Cracking 饱和多缝开裂的缺陷分布设计 Superimpose artificial flaws with prescribed sizes Artificial flaws: plastic, bubbles, lightweight aggregates, etc. cmc = func (fiber bridging, matrix toughness) LEFM Failed to Predict Cracking StrengthLEFM预测开裂强度失败 Cohesive Crack Model 粘着裂缝模型 FEM Model of Cracking 开裂模型 Cracking Strength of Mortar 砂浆开裂强度 Cracking Strength of PVA-ECC 开裂