高性能水泥基复合材料断裂性能

Fracture Performance of High-Performance Cement-Based Composites

对钢纤维体积分数为0%、1%和2%的高性能水泥基复合材料(HPCC)带预制裂缝梁试件进行了三点弯曲测试,通过荷载-裂缝嘴张开位移(F⁃CMOD)曲线系统分析了试件的弯曲强度、残余强度以及起裂韧度、失稳韧度、断裂能、脆性指数等,并对其断裂面形态进行了扫描电镜测试.结果表明:钢纤维体积分数对HPCC弯曲强度、残余强度影响显著,而对起裂韧度没有影响;掺钢纤维后HPCC失稳韧度增幅可达8倍以上,但钢纤维体积分数对HPCC失稳韧度提升具有一定的限值,约为1%;掺钢纤维后HPCC断裂能大幅提升,且随着钢纤维体积分数的增加而增加;掺钢纤维能有效降低HPCC脆性,但更高的钢纤维体积分数对HPCC脆性的降幅不显著;HPCC加载初期微裂纹的形成与扩展主要由基体自身性能决定,钢纤维失效经历了纤维与基体脱黏和剥离的过程,失效模式为钢纤维拔出,钢纤维并未发生断裂.

Three⁃point bending tests were carried out on high⁃performance cement⁃based composites(HPCC)using notched beams with different fiber contents(0%,1%,2%).Bending strength,residual strength,initial fracture toughness,unstable fracture toughness,fracture energy,and brittleness were analyzed from the obtained F⁃CMOD curves,and the fracture surface was tested by scanning electron microscope(SEM).The results show that steel fiber content has a significant effect on bending strength and residual strength,but the initial fracture toughness is not affected by steel fiber content.The unstable fracture toughness of HPCC with steel fibers can increase over 8 times,but the steel fiber content has a certain limit about 1%on the unstable fracture toughness improvement of HPCC.The fracture energy of HPCC with steel fibers is greatly improved,and increases gradually with the increase of steel fiber content.Steel fiber can effectively reduce the brittleness of HPCC,but higher steel fiber content has no significant effect on the brittleness of HPCC.Formation and propagation of microcracks in HPCC at the initial stage of loading are mainly determined by the property of the cement matrix.The failure of steel fibers has undergone a process of debonding and peeling between fiber and matrix.The failure mode is that the steel fiber is pulled out without breaking.