不同龄期钢纤维增强水泥砂浆纤维拉拔试验与模拟研究

Experimental and Numerical Studies on Fiber Pull-Out of Steel Fiber Reinforced Cement Mortar at Different Ages

钢纤维增强水泥基复合材料作为一种多相复合材料,其增强增韧效果的发挥依赖于钢纤维与基体之间的界面粘结性能。通过开展不同龄期的钢纤维增强水泥基复合材料单根纤维拉拔试验及数值模拟研究,分析了龄期对钢纤维增强水泥砂浆界面粘结性能的影响,建立了不同龄期的单根纤维拉拔细观模型,通过将模拟结果与试验结果进行对比验证模型的有效性。根据所建立的细观模型分别对不同龄期钢纤维增强水泥砂浆纤维-基体间的界面粘结作用机理及纤维-基体间粘结表面在纤维拔出过程中的应力变化进行了分析。结果表明:所建立细观模型模拟得到的纤维最大拉拔力及荷载-滑移曲线与试验结果吻合较好,钢纤维的最大拉拔力及钢纤维-水泥砂浆基体的界面粘结强度均随着龄期的增加而增加;在7 d龄期内界面粘结强度的增长速度较快,7 d龄期后增长速度放缓;随着龄期的增加,不同龄期段的界面粘结强度的增长率逐渐减小并趋于稳定。采用拟合得到的粘结表面材料参数能够有效模拟各龄期下单根钢纤维从水泥砂浆中的拔出过程。

As a kind of multiphase composite,the reinforcement and toughening effect of steel fiber reinforced cementitious composite depends on the interfacial bonding properties between steel fiber and matrix.According to the single fiber pullout tests and numerical simulation of the steel fiber reinforced cement mortar at different ages,the effects of ages on the interfacial bond properties of steel fiber reinforced cement mortar were studied.A meso-scale model of single fiber pull-out tests of the steel fiber reinforced cement mortar at different ages was established and verified by comparison with the simulated and tested results.The mechanism of interfacial bond between fiber and matrix of steel fiber reinforced cement mortar at different ages and the stress variation of the section around the interface between steel fiber and cement mortar matrix were analyzed by this model.The results show that,the simulated peak pull-out load and the pull-out curves are in good agreement with the tested results.Both the peak pull-out load of steel fiber and the interfacial bond strength between steel fiber and cement mortar matrix increase with the increase of age.The interfacial bond strength increases rapidly in the stage of the first 7 d,then slows down.The growth rate of interfacial bond strength in different age periods gradually decreases and tends to be stable with the increase of ages.The fitted mechanical parameters of the interface between steel fiber and cement mortar effectively simulate the pull-out process of the steel fiber.