不同应变率和碳纳米管掺量下混凝土的力学性质与能量演化特征

Mechanical Properties and Energy Evolution Characteristics of Concrete under Different Strain Rates and Content of MWCNTs

为研究应变率(加载速率)和多壁碳纳米管掺量对碳纳米管混凝土试样力学性质、能量演化规律及损伤破坏特征的影响,采用RMT-150B岩石力学试验系统,对不同应变率下不同碳纳米管掺量的混凝土试样开展了系列单轴压缩试验。试验结果表明:碳纳米管混凝土试样的延性随着多壁碳纳米管掺量的增加而增大;当应变率恒定时,多壁碳纳米管掺量为0.1%的改性碳纳米管混凝土的单轴抗压强度最大;当多壁碳纳米管掺量恒定时,应变率为5×10−3 s−1(0.5 mm/s)时碳纳米管混凝土试样的单轴抗压强度最大;当应变率较大时,在试样峰值应力处,碳纳米管混凝土的能量耗散值占总能量的28.29%;当应变率较小时,试样峰前阶段的能量耗散现象显著,峰值应力处耗散能占比平均高达37.34%;当应变率和多壁碳纳米管掺量均较小时,碳纳米管混凝土在破坏前所吸收的能量大量转化为耗散能,峰后试样能量释放率较小,表现为局部张拉与剪切混合破坏特征;当应变率和多壁碳纳米管掺量均较大时,碳纳米管混凝土在破坏前所吸收的能量主要储存为可释放弹性应变能,在破坏时混凝土试样的能量释放速率较高,碳纳米管混凝土试样破坏时较为破碎,一定程度上表现出冲击破坏的特征。

In order to study the effect of strain rate(loading rate)and multi-walled carbon nanotubes(MWCNTs)content on the mechanical properties,energy evolution law and damage failure characteristics of MWCNTs-reinforced concrete samples,the RMT-150B rock mechanics test system was used to carry out a series of uniaxial compression tests on MWCNTs-reinforced concrete samples with different content of MWCNTs under different strain rates.The results show that the ductility of MWCNTs-reinforced concrete samples increases with the increase of the content of MWCNTs.When the strain rate is constant,the uniaxial compressive strength of the MWCNTs-reinforced concrete with 0.10%MWCNTs content is the highest;when the content of MWCNTs is constant,the uniaxial compressive strength of the MWCNTs-reinforced concrete samples reaches the maximum under strain rate of 5×10–3 s–1(0.5 mm/s);when the strain rate is large,the mean value of the energy dissipation of MWCNTs-reinforced concrete accounts for 28.29%of the total energy at the peak stress.When the strain rate is small,the energy dissipation phenomenon in the pre-peak stage is significant,and the mean proportion of dissipated energy at the peak stress is as high as 37.34%.When the strain rate and MWCNTs content are small,the energy absorbed by the MWCNTs-reinforced concrete before failure is largely transformed into dissipative energy,and the energy release rate of the samples after peak stress is small,which is characterized by mixed failure of local tension and shear.When the strain rate and MWCNTs content are large,the energy absorbed by the MWCNTs-reinforced concrete before failure is mainly stored as releasable elastic strain energy,and the energy release rate of the concrete samples is faster at failure,and the MWCNTs-reinforced concrete samples are relatively broken at failure,showing the characteristics of impacted damage to a certain extent.