超高韧性水泥基复合材料多次冲击压缩性能及本构关系

MULTIPLE IMPACT COMPRESSIVE PROPERTIES AND CONSTITUTIVE MODEL OF ULTRA-HIGH TOUGHNESS CEMENTITIOUS COMPOSITES

  • 摘要: 利用直径80 mm分离式霍普金森压杆(SHPB)系统进行了超高韧性水泥基复合材料(ultra high toughness cementitious composites,UHTCC)在多次冲击压缩荷载下力学性能的研究,分析了试件的应力-应变曲线随冲击次数的演化规律, 并与其他纤维增强混凝土进行对比。试验结果表明:在多次冲击荷载作用下由于损伤的累积导致加载应变率随冲击次数增加而大致呈指数递增,UHTCC的峰值强度随应变率增大而近似线性递减,峰值应变和累积吸能值逐渐增加,单次吸能值随冲击次数的增加呈先增后减的变化趋势。通过对本构模型进行探讨后发现,热激活损伤演化(TADE)模型能较好地描述UHTCC在首次冲击下的力学响应,但无法反映其在多次冲击下力学性能的演化规律;基于Weibull分布的损伤演化模型能够较好地描述UHTCC在多次冲击下的累积损伤演化规律及应力-应变曲线,在经历3次冲击作用后根据损伤程度的计算可认为试样已完全破坏,但此时试样通过PVA纤维的桥连作用仍能保持为整体,具有良好的抗破碎性。

     

    Abstract: The mechanical properties of ultra-high toughness cementitious composites (UHTCC) under multiple impacts were studied using an 80-mm split Hopkinson pressure bar (SHPB). The evolution law of the stress-strain curve under different numbers of impacts was analyzed and compared with that of other fiber reinforced concrete. The experimental results show that under multiple impact loads, the strain rate increased exponentially with the increase of the number of impacts due to damage accumulation. The peak strength of UHTCC decreased linearly with the strain rate, while the peak strain and cumulative energy absorption increased gradually. The single energy absorption value increased first and then decreased with the increase of the number of impacts. The thermal activated damage evolution (TADE) model could only describe the mechanical response of UHTCC upon the first impact, but could not reflect the evolution law of the mechanical properties under multiple impacts. Comparatively, the damage evolution model based on Weibull distribution could well reflect the cumulative damage evolution law and the stress-strain curves of UHTCC under multiple impacts. According to the calculation of the damage degree, the sample could be considered to have been completely damaged after the third impact. However, the sample could still be kept as a whole by the bridging effect of the PVA fibers. It demonstrated its good crushing resistance capacity.

     

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