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混凝土细观结构形式及其力学性能决定混凝土宏观力学性能及损伤破坏模式。从细观角度出发,将混凝土看作由骨料、砂浆基质和界面过渡区组成的三相复合材料,建立了混凝土二维随机骨料有限元模型。采用耦合材料应变率效应的塑性损伤本构模型来描述砂浆基质及界面过渡区的力学性能;认为骨料不产生损伤破坏,为弹性体。对不同加载速率下双边缺口混凝土试件的拉伸破坏模式及混凝土梁动态弯拉破坏过程进行了数值研究,探讨了界面过渡区对混凝土破坏模式及宏观力学性能的影响。数值结果表明当加载速率较小时,界面过渡区的力学性能对混凝土拉伸、弯拉破坏模式和宏观力学性能有显著的影响;而当加载速率很大时,如冲击载荷作用(名义应变率>50 s-1)下混凝土动态拉伸破坏模式及混凝土梁弯拉破坏模式基本不受界面过渡区力学性能的影响。因此,在对高速冲击、碰撞或爆炸下关于混凝土拉伸破坏的数值研究中可忽略界面过渡区的影响。
The meso-structure of concrete and its mechanical properties determine the macroscopic mechanical properties of concrete and damage damage modes. From a microscopic point of view, concrete is considered as a three-phase composite material composed of aggregate, mortar matrix and interfacial transition zone, and a two-dimensional random aggregate finite element model of concrete is established. The plastic damage constitutive model was used to describe the mechanical properties of the mortar matrix and interface transition zone. It is considered that the aggregate does not produce damage and damage and is an elastomer. The tensile failure modes of double-notched concrete specimens under different loading rates and the dynamic bending and failure process of concrete beams were studied numerically. The influence of interface transition zone on the failure modes and macroscopic mechanical properties of concrete was also discussed. Numerical results show that when the loading rate is small, the mechanical properties of the interface transition zone have a significant effect on the tensile, flexural failure modes and macroscopic mechanical properties of the concrete. However, when the loading rate is large, such as the impact load (nominal strain rate> 50 s-1) under dynamic tensile failure mode and the concrete beam bending failure mode is basically not affected by the interface transition zone mechanical properties. Therefore, in the high-speed impact, collision or explosion on the tensile failure of concrete numerical study can ignore the interface transition zone.