【作者】 刘丹；

【导师】 许莉；

【作者基本信息】 天津大学 ， 化工过程机械， 2010， 硕士

【摘要】 质子交换膜(PEM)是质子交换膜燃料电池(PEMFCs)的关键部件,其可靠性对燃料电池寿命有着至关重要的影响,研究其力学性能具有重要意义。本文利用动态力学分析仪(DMA-Q800)对PEM的基本力学性能进行了测试,考察了Nafion?-212在工作温度(85℃)下,受到循环应力作用时,其棘轮应变和棘轮应变率的变化情况,得出平均应力,应力幅,应变率等因素对材料棘轮应变的影响;还研究了其在高温(70℃)浸泡环境下的相关力学性能,有浸泡时间,应变率及是否浸泡对其拉伸性能的影响,还有是否浸泡,应力大小等对其棘轮效应的影响。结果表明,Nafion?-212为率相关材料,高温下应变率对其切线模量,棘轮应变及棘轮应变率均有影响,而高温下平均应力,应力幅等对其循环加载性能也有不同程度的影响;在去离子水中浸泡对其性能有着一定的影响,试样在相同应变下的应力值随着浸泡时间的增加而增大,但是浸泡24小时左右,试样的拉伸性能就趋于稳定,浸泡与否对试样棘轮变化趋势影响不大,但在相同的应力水平下,非浸泡试样的棘轮应变明显大于浸泡试样的。本文还选取了一种国产质子交换膜,研究了其在应变率控制下,在不同温度,加载率条件下的力学性能,包括拉伸性能,蠕变-恢复性能,应力松弛性能等,得出了此种PEM的弹性模量,应力,应变与温度、加载率的关系;在研究聚合物本构关系的基础上,研究了其蠕变随时间,温度,应力变化的蠕变公式,并进行了预测。结果表明,GEFC?-105基于Tan Delta的玻璃化转变温度略高于Nafion?-212;拉伸试验中,在相同的加载条件下,GEFC?-105材料的切线模量、屈服值以及相同应变下的应力值都要大于Nafion?-212的;蠕变试验中,随着应力的增大,试样经过相同时间的蠕变应变快速地增加,温度越高这种现象越明显,而相同蠕变时间的应变随温度的升高快速的增大;松弛试验中,试样的初始应变越大,其产生的初始应力也越大,应力先是快速下降,然后逐渐趋于稳定,而在相同初始应变下,温度越高,其产生的初始应力越低,在整个松弛过程中,其应力也越低;本文应用改进后的Findley蠕变模型预测的蠕变曲线效果比较好。更多还原

【Abstract】 The Proton Exchange Membrane (PEM) is the crucial part of Proton Exchange Membrane Fuel Cells (PEMFCs) and its reliability has essential influence on the life of PEMFCs, so it is important to study the mechanical properties of PEMs.The Dynamic Mechanical Analyser (DMA-Q800) is used to test the basic mechanical properties in this work. The Nafion? -212 was exerted the cyclic stresses at its operating temperature(85℃), and the change of its ratcheting strain and strain rate was observed. Moreover, the effect of mean stress, stress amplitude and strain rate to the ratcheting strain were investigated. In addition, its mechanical properties in the soaking environment of high temperature(70℃) was studied too. Besides the research of the effect of soaking time, strain rate and soaking or not soaking on the tensile property, the effect of stress and soaking or not soaking on the ratcheting behavior was studied. The tests results indicated that Nafion? -212 was rate dependent material and the strain rate affected its tangent modulus, ratcheting strain and strain rate at high temperatures. Else, the mean stress, stress amplitude etc. had different influence on its cyclic loading properties. Being soaked in the deionized water had certain effect on its mechanical properties. The stress of specimen at the same strain level was increased as the increase of soaking time. But the tensile property tended to become stable after the specimen was soaked for 24 hours. The effect of soaking or not was small on the ratcheting trend, while the ratcheting strain of no soaked specimen was bigger than that of soaked specimen under the same stress level.The mechanical properties (tensile property, creep-recover property, stress relaxation) of a kind of domestic PEM were studied under different temperatures and strain rates with strain controlled methods. The relationship between elastic modulus, stress, strain and temperature, loading rate was obtained. The experimental results indicated that the glass transition temperature of GEFC?-105 based on Tan Delta was slightly higher than Nafion?-212. In the creep-recover test, the creep strain increased quickly with the increase of stress, and the increase was more significant as the temperature went higher. Additionally, the creep strain increased slightly as the increase of temperature too. In the relaxation tests, the bigger the initial strain, the bigger the initial stress. And the stress declined rapidly first, then reached equilibrium gradually. While under the same strain level, the higher the temperature, the lower the initial stress and the stress within the whole relaxation progress. Based on the research of the constitutive relation of polymer, a creep equation involving time, temperature, stress was studied. Moreover, the creep curves at various temperatures were predicted. The prediction of creep curves used with the improved Findley creep model was good.更多还原