摘要
为探讨环氧基形状记忆聚合物(ESMP)在大应变状态下由材料超弹-黏弹性引起的应力软化-刚化效应及率相关特性,针对玻璃化转变温度(T_g)附近ESMP在发生大变形时表现出的应力软化和刚化效应进行力学本构方程及其试验研究.利用2阶多项式的超弹性本构方程替换广义Maxwell模型中的线弹性胡克定律以考虑大应变条件下材料的刚化效应,构造出超弹-黏弹性本构方程,并在真应变速率恒定的条件下推导出具有解析表达式、便于工程应用的材料参数测定公式;采用分段线性位移曲线逼近指数变化位移曲线,在温度高于T_g点的橡胶态及低于T_g点7℃的状态下,分组进行不同应变率的ESMP单轴拉伸试验;利用试验数据拟合得到推导本构方程的材料参数,并对其相应的拉伸试验进行数值模拟,试验结果与模拟结果较为吻合.结果表明:ESMP具备明显的率相关特性;随着应变速率的增大,ESMP的软化效应及刚化效应有所增强;应变速率大的切线模量总是大于应变速率小的切线模量.
In order to investigate the stress softening-stiffening effect and the rate-dependent properties caused by the hyper-viscoelasticity of epoxy shape memory polymer(ESMP)in large strain regime,this work makes attempt to reveal the softening and stiffening effect of ESMP near and above glass transition temperature(T_g).Firstly,to account the stiffening effect in large strain,a hyper-viscoelastic model is established by substituting the second-order polynomial hyper-elastic model to the linear Hooke’s law in generalized Maxwell model.Meanwhile,the material constants calibration equations which are convenient for engineering application are derived for the case of constant true strain rate in analytical form.Then,the tensile tests in various strain rates are carried out at temperature above T_g in rubbery state and 7℃blow T_g,where the exponential tensile displacement curve are approached by finite pieces of linear displacement curve.The material constants are calibrated by the tests respectively.The numerical simulation of each test is carried out using the corresponding parameters,where the simulation results are found to have high consistency with the test results.The results indicate that ESMP behaviors significant rate-dependence.Meanwhile,the softening effect and the stiffening effect increase with increasing strain rate;the tangential modulus in a large strain rate is always greater than the tangential modulus in a small strain rate.
作者
樊鹏玄
陈务军
胡建辉
赵兵
房光强
曹争利
彭福军
FAN Pengxuan;CHEN Wujun;HU Jianhui;ZHAO Bing;CAO Zhengli;PENG Fujun(Space Structures Research Center,Shanghai Jiao Tong University,Shanghai 200240,China;Shanghai Aerospace System Engineering Research Institute,Shanghai 201108,China)
出处
《上海交通大学学报》
EI
CAS
CSCD
北大核心
2019年第9期1017-1022,共6页
Journal of Shanghai Jiaotong University
基金
航天先进技术联合研究中心技术创新项目(USCAST2015-24,USCAST2016-21)
关键词
环氧基形状记忆聚合物
大应变
超弹-黏弹性
率相关
刚化效应
epoxy shape memory polymer(ESMP)
large strain
hyper-viscoelasticity
rate-dependence
stiffening effect
