钢纤维增强粉煤灰地质聚合物单轴受压过程的声发射特性

为探索纤维增强地质聚合物宏观力学行为与细观损伤演化特征之间的关联,对不同纤维体积掺量(纤维与拌合物的体积比)的钢纤维增强粉煤灰地质聚合物复合材料进行了单轴压缩试验.基于声发射技术,对试样压缩过程的声发射行为进行监测,研究了纤维体积掺量对地质聚合物单轴受压破坏行为及声发射特性的影响.结果表明:地质聚合物的强度、延性、声发射波形的上升斜率及平均频率均随纤维掺量的提高而增大,试件破坏形态由脆性灾变逐渐向延性破坏转变;在破坏前期,纤维体积掺量为0及0.5%的试件的声发射撞击率及能量释放率(简称能量率)都保持在较高水平,最终导致试件出现灾变破坏;而2.0%的纤维体积掺量使得声发射撞击率及能量率在应力-时间曲线的拐点处达到峰值,随后缓慢下降,最终导致试件呈现延性破坏;因此,仅依据声发射撞击率及能量率的快速上升来预测灾变破坏的发生,有时可能会出现谎报的情况.

Acoustic emission behavior of steel fiber reinforced fly ash geopolymer under uniaxial compression

In order to investigate the relationship between the macroscopic mechanical behavior and mesoscopic damage evolution characteristics of fiber reinforced geopolymer samples, a series of uniaxial compression tests were carried out on steel fiber reinforced fly ash geopolymer composites with different fiber volume contents (the volume ratios of fiber to mixture). Based on the acoustic emission technique, the acoustic emission behaviors during the compression process of samples were monitored. The influence of fiber volume contents on the failure behavior and the characteristics of acoustic emission of geopolymer under uniaxial compression was investigated. The results show that the strength, ductility, the increasing slope and average frequency of acoustic emission waveform increase as the fiber content increases, and the failure mode of the samples changes from brittle catastrophic pattern to ductile pattern gradually. In the earlier stage of destruction, the acoustic emission hit rate and energy release rate (abbreviate energy rate) of samples with the fiber volume content of 0 or 0.5% maintain a higher level, and finally leads to the catastrophic rupture of the samples. However, the fiber volume content of 2.0% makes the acoustic emission hit rate and the energy rate reach the peak at the inflection point of stress-time curve, and then decrease slowly, leads to the ductile rupture of samples finally. Therefore, predicting the occurring of catastrophic rupture depends on the rapid increasing of acoustic emission hit rate or energy rate simply, may gives false information sometimes.