Experimental and numerical analysis of micromechanisms of fracture of cement-based composites
Experimental and numerical analysis of micromechanisms of fracture of cement-based composites
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DOI：
10.1016/0958-9465(92)90004-f
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发表时间：
1992
影响因子：
10.5
通讯作者：
E. Schlangen;J. Mier
中科院分区：
文献类型：
--
作者：
E. Schlangen;J. Mier
本文提出了通过称为裂纹面桥接的机制实现混凝土和砂浆断裂增韧的实验证据。混凝土软化的经典解释，即。在连续宏观裂纹之前形成不连续微裂纹区域似乎只是部分正确。相反，宏观裂纹尖端之后的裂纹面桥接似乎是物理上更合理的解释。裂纹面桥是重叠裂纹尖端之间的弯曲韧带。由于两个重叠的裂纹尖端相互屏蔽，弯曲韧带的失效以稳定且受控的方式发生。宏观裂纹上的内聚应力与裂纹面桥的尺寸直接相关，而裂纹面桥的尺寸取决于材料的异质性。可以使用简单的数值晶格模型来模拟典型的失效机制。首先，通过手动方法或采用随机生成器生成材料的晶粒结构。其次，将脆性断裂梁单元的三角形晶格投影到晶粒结构上。骨料、基体和粘结属性被分配给相应位置的晶格单元，并且简单的算法允许进行裂纹扩展模拟。主要结论是，裂纹模式和相关的载荷变形响应很大程度上取决于成分的特性。骨料和基体之间的结合是系统中最薄弱的环节，该参数的变化会导致截然不同的裂纹模式。
In this paper experimental evidence of fracture toughening of concrete and mortar through a mechanism called crack face bridging is presented. The classical explanation for softening of concrete, viz. the formation of a zone of discontinuous microcracking ahead of a continuous macrocrack seems only partially true. Instead, crack face bridging in the wake of the macrocrack tip seems a physically sounder explanation. The crack face bridges are flexural ligaments between ovelapping crack tips. The failure of the flexural ligaments occurs in a stable and controlled manner because the two overlapping crack tips shield each other. The cohesive stress over the macrocrack is directly related to the size of the crack face bridges, which depends on the heterogeneity of the material.The typical failure mechanism can be simulated using a simple numerical lattice model. First the grain structure of the material is generated either by manual methods or by adopting a random generator. Secondly a tringular lattice of brittle breaking beam elements is projected on the grain structure. Aggregate, matrix and bond properties are assigned to the lattice elements at the respective locations, and a simple algorithm allows for crack growth simulation. The main conclusion is that the crack patterns and the associated load-deformation response are largely governed by the properties of the constituents. The bond between aggregates and matrix is the weakest link in the system, and variation of this parameter leads to profoundly different crack patterns.