短纤维水泥基复合材料的拉伸数值分析

提出软弱区的概念,并定义该软弱区为砂浆试件中包含微裂隙、微裂缝或微缺陷的一个局部区域,采用细观力学的方法,假定砂浆试件是由砂浆基体和许多随机分布于基体中的软弱区所组成,基于蒙特卡罗随机抽样原理,实现软弱区单元在砂浆基体中的随机分布,基体单元和软弱区单元材料的非均匀性由Weibull参数来表征,同时假定基体单元和软弱区单元均符合低拉伸材料开裂准则,建立砂浆拉伸数值模型,考虑软弱区分布、Weibull分布参数、细观单元力学参数等对数值试验的影响,全面分析砂浆拉伸开裂的力学行为。在砂浆数值模型的基础上,系统研究短纤维增强砂浆的拉伸开裂及纤维细观力学参数、分布特征等对数值拉伸结果的影响。最后,将数值结果与试验结果进行对比,结果表明,数值模型能较好地模拟砂浆的拉伸开裂和短纤维对砂浆的增强效果,同时由数值模拟得到的砂浆单向拉伸应力–应变全过程曲线与试验结果较为吻合。

NUMERICAL ANALYSIS OF SHORT FIBER REINFORCED CEMENT-BASED COMPOSITES IN DIRECT TENSION

soft region was defined as a local region including microcrack,microdefect,etc.based on mesoscopic mechanics method;and it was assumed that mortar specimen was composed of mortar matrix and many soft regions are distributed in the matrix.In terms of Monte Carlo random sampling principle,it could be acquired that soft region elements are randomly distributed in the matrix.Material heterogeneity of matrix elements and soft region elements were depicted with Weibull parameters,and matrix elements and soft region elements were in accordance with low tension crack law,thus mortar tension numerical model can be built.Considering effects of distribution of soft regions,Weibull distribution parameters,mesoscopic element mechanical parameters on numerical experiments,the mechanical behaviors of mortar tension crack are analyzed.Based on mortar tension numerical model,short fiber reinforced mortar numerical model that was treated as three-phase composites including matrix,soft region and short fiber,was also built.With the numerical model,tension crack behavior of short fiber reinforced mortar was researched;the effects of fiber mesoscopic mechanical parameters such as fiber length,fiber diameter,fiber distribution characters on numerical tension results were also analyzed.Finally,numerical results were compared with experimental data,and the results display that numerical model can successfully simulate mortar tension crack and strengthening character of short fibers with mortar.The complete curve of mortar tension stress-strain agrees well with experimental results.