Understanding the dynamic mechanical behaviors of materials is a prerequisite for reliably analyzing and predicting the dynamic response of structures, which is of great significance for transportation infrastructure and military engineering subjected to extreme loads, particularly dynamic loads at high strain rates. Nickel coated multi-walled carbon nanotubes (Ni-MWCNTs) show promise as a reinforcement to modify the dynamic mechanical behaviors of ultra-high performance cementitious composites (UHPCC). Because Ni-MWCNTs combine the high tensile strength and large aspect ratio characteristics of fibers with the nano effect of nanomaterials, as well as have excellent dispersibility due to the nickel plating on the CNTs’ surface, they effectively improve the dynamic mechanical properties of UHPCC under impact loading at high strain rates of about 100 s/300 s/500 s and reduce the brittle damage degree of composites. The maximal increase in dynamic compressive strength and energy absorption capacity of UHPCC reaches 47.9% and 68.2%, respectively. This enhancement effect arises from that Ni-MWCNTs improve the microstructure and form multiple fine cracks, resulting in an increased energy consumption required for crack formation, propagation and coalescence. Additionally, the dynamic mechanical properties of Ni-MWCNTs reinforced UHPCC exhibit noticeable strain rate effects. Consequently, a strain rate-dependent logarithmic functional dynamic increase factor model and dynamic constitutive model of UHPCC filled with Ni-MWCNTs are modified herein for predicting and modeling the dynamic mechanical behaviors of composites.

中文翻译：

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镍涂层碳纳米管增强超高性能水泥基复合材料在高应变率冲击载荷下的动态行为

了解材料的动态力学行为是可靠分析和预测结构动态响应的先决条件，这对于承受极端载荷，特别是高应变率动态载荷的交通基础设施和军事工程具有重要意义。镀镍多壁碳纳米管（Ni-MWCNT）有望作为增强材料来改变超高性能水泥基复合材料（UHPCC）的动态机械行为。由于Ni-MWCNTs将纤维的高拉伸强度和大长径比特性与纳米材料的纳米效应相结合，并且由于CNT表面镀镍而具有优异的分散性，因此有效提高了UHPCC在高温下的动态力学性能。在约100 s/300 s/500 s的高应变速率下承受冲击载荷，降低复合材料的脆性损伤程度。 UHPCC的动压强度和吸能能力最大增幅分别达到47.9%和68.2%。这种增强效应源于Ni-MWCNT改善了微观结构并形成多个细裂纹，导致裂纹形成、扩展和聚结所需的能量消耗增加。此外，Ni-MWCNT 增强 UHPCC 的动态机械性能表现出明显的应变率效应。因此，本文修改了填充 Ni-MWCNT 的 UHPCC 的应变率依赖性对数函数动态增加因子模型和动态本构模型，用于预测和建模复合材料的动态力学行为。