冲击荷载下高温喷淋冷却碳纳米管混凝土破裂分形研究  

A study on fracture fractal of high temperature spray cooled carbon nanotube concrete under impact load

作　　者：田威[1] 高芳芳 TIAN Wei;GAO Fangfang(School of Civil Engineering,Chang’an University,Xi’an 710061,China)

机构地区：[1]长安大学建筑工程学院,西安710061

出　　处：《振动与冲击》2023年第4期71-80,共10页Journal of Vibration and Shock

摘　　要：在混凝土中掺入具有高强、高韧和良好热导性的多壁碳纳米管(multi walled carbon nanotubes, MWCNTs)对普通混凝土的耐高温性能进行了增强,并以分形维数为指标研究了高温喷淋冷却后碳纳米管增强混凝土在冲击荷载作用下的分形特征和能耗特性,建立了分形维数与动强度、能耗及冲击韧性之间的关系。研究结果表明:高温喷淋冷却后的混凝土在冲击载荷下,其冲击破碎块的分形维数随应变速率和温度的增大而增大;在同一温度下,混凝土的动态抗压强度、能耗和冲击韧性随着分形维数的增加而增加;在同一冲击气压下,混凝土的动态抗压强度、能耗和冲击韧性随着分形维数的增加而减小;相比而言,添加了碳纳米管后混凝土高温喷淋冷却后在冲击荷载下的破裂程度得到有效缓解,其分形维数减小,能耗、冲击韧性和动强度都得到明显提高。In order to improve the impact resistance of concrete after high temperature, multi walled carbon nanotubes(MWCNTs) with high strength, high toughness, and good thermal conductivity were added into the concrete. And the fractal characteristics and energy consumption characteristics of carbon nanotube reinforced concrete under impact loading after high temperature were explored by the fractal index(i.e. fractal dimension), and the relationship between fractal dimension and dynamic compressive strength, energy consumption and impact toughness was established. Results show that after high temperature, the fractal dimension of concrete impact fracture increases with the increase of strain rate and temperature under impact load. At the constant temperature, the dynamic compressive strength, energy consumption and impact toughness of concrete increase with fractal dimension, while at the constant impact pressure, they perform opposite trend. Meanwhile, compared with ordinary plain concrete, concrete incorporating with multi walled carbon nanotubes owns light crushing degree, small fractal dimension, high energy consumption, impact toughness and dynamic compressive strength. In fact, the variation of fractal dimension essentially depends on the compactness of concrete and the propagation degree of internal crack. Well dispersed multi walled carbon nanotubes in concrete could not only refine pores, but also provide attachment points for hydration products and promote hydration process, so as to improve the compactness of concrete matrix. Besides, the bridging, pullout and thermal conductivity of multi walled carbon nanotube are also conducive to inhibit and delay the initiation and propagation of temperature cracks and load cracks. Consequently, the resistance of concrete with multi walled carbon nanotubes to high temperature and impact load has been effectively improved.

关 键 词：混凝土 多壁碳纳米管(MWCNTs) 高温喷淋 冲击荷载 分形维数 

分 类 号：TU525.9[建筑科学—建筑技术科学]