纳米二氧化硅改性超高韧性水泥基复合材料冲击压缩试验研究

该文采用Ф80 mm的分离式霍普金森压杆装置，研究了纳米改性后的UHTCC（ultra high toughness cementitious composites）在高速冲击压缩应力状态下的力学响应，并与常规UHTCC材料、钢纤维混凝土进行了对比。试验得到了各组材料在准静态和动态共计4组应变率（2.36×10-5 s-1、120 s-1、160 s-1、200 s-1）下的准静态压缩强度及冲击压缩应力-应变曲线，并计算了各组试件的耗能能力。为了进一步优化材料的抗冲击性能，该文还研究了纳米改性后的UHTCC基体中钢纤维和PVA纤维的混杂效果。试验结果表明:5组材料均具有应变率敏感性，峰值应力和耗能能力随着应变率的增大而上升；经过纳米改性后的UHTCC材料冲击压缩力学强度及耗能能力明显提高；在冲击荷载下，钢纤维和PVA纤维产生正混杂效应，提高钢纤维掺量可以强化UHTCC的抗冲击能力；应变率的大小和钢纤维的掺量之间的关系影响了动态峰值应力的提升。

IMPACT COMPRESSION PROPERTIES OF NANO-SIO2 MODIFIED ULTRA HIGH TOUGHNESS CEMENTITIOUS COMPOSITES USING A SPLIT HOPKINSON PRESSURE BAR

Ф80 mm Split Hopkinson Pressure Bar was used to study the dynamic compressive behavior of nano-SiO₂ modified UHTCC (Ultra High Toughness Cementitious Composite), and it was compared with that of steel fiber reinforced concrete and normal UHTCC. The quasi-static compressive strength and stress-strain curves under dynamic loads with 4 strain rates (2.36×10-5 s-1, 120 s-1, 160 s-1, 200 s-1) were achieved in this experiment. Moreover, hybrid fiber effect of PVA and steel fiber on the impact resistant ability of materials was also studied in this research. The results showed that the peak compressive strength and specific energy absorption rose along with the increase of the strain rate for all groups. The dynamic stress and energy absorption ability of nano-SiO₂ modified UHTCC were higher than normal UHTCC. Besides, steel-PVA fibers had synergy on the dynamic behavior of UHTCC and it was improved with the steel fiber content increasing. However, the improvement of dynamic stress was dependent on synergistic relationship between the strain rate and the steel fiber addition.