钢纤维砂浆纳米压痕微观断裂性能表征

Micro Fracture Characterization of Steel Fiber Reinforced Mortar by Nanoindentation

钢纤维砂浆为多相复合材料,传统宏观试验方法难以表征其中各相的微观断裂参数,因此无法明确材料宏观断裂性能的微观机理。基于纳米压痕技术,研究了钢纤维砂浆中主要组成相的微观断裂性能。根据压痕能量法基本原理和加载、卸载过程的荷载—位移曲线特征,建立了考虑持荷作用的塑性能显式计算公式。通过该式和压痕曲线能够直接计算材料断裂能、能量释放率和断裂韧度。结果表明：基于纳米压痕技术的微观断裂研究方法能够得到稳定的净浆基体和石英砂的断裂韧度值,且该值与宏观断裂测试方法得到的断裂韧度数据一致,但低估了钢纤维的断裂韧度。该方法只适用于准脆性材料断裂性能的估算。

Steel fiber reinforced mortar （SFRM） is a multiphase composite. Since it is difficult to determine the micro fracture properties of the phases by conventional macro methods, the microscopic mechanism behind the macro fracture is still unclear. The fracture properties of the main solid phases in a SFMR in micro scale were investigated by an energy-based fracture characterizing method based on nanoindentation. An explicit formula of plastic energy with load-holding effect was proposed based on the whole load-displacement curves of an indentation test. The fracture energy, energy release rate and fracture toughness of the phases in the SFRM were calculated directly from the indentation curves via this formula. The results show that the indentation characterizing method provides the stable fracture data of the cement matrix and quartz in the SFRM, which are comparable with those by the conventional macro fracture tests, but underestimates those of the steel fiber. The method may be suitable for characterizing the fracture properties of quasi-brittle materials.