表面直接氟化改性对有机玻璃弯曲疲劳性能的影响  

Effect of Surface Modification by Direct Fluorination on Bending Fatigue Behaviors of Poly (Methyl Methacrylate)

作　　者：夏炎 朱忠猛 蒋晗[1] Yan Xia;Zhongmeng Zhu;Han Jiang(School of Mechanics and Engineering,Southrwest Jiaotong University,Chengdu,610031)

机构地区：[1]西南交通大学力学与工程学院,成都610031

出　　处：《固体力学学报》2020年第1期71-82,共12页Chinese Journal of Solid Mechanics

基　　金：国家自然科学基金面上项目(11872322);四川省应用基础研究重点项目(2019YJ0231)资助。

摘　　要：论文使用表面直接氟化改性来改善有机玻璃的弯曲疲劳性能.测试了改性前后有机玻璃的断裂韧性与弯曲强度,重点研究了不同缺口形式的有机玻璃在改性前后的弯曲疲劳性能变化并分析了疲劳裂纹扩展过程.弯曲疲劳寿命的测定结果表明有机玻璃的疲劳性能在表面直接氟化改性后得到明显改善,表面氟化层的结构约束效应是有机玻璃疲劳寿命提高的主要原因.此外,在疲劳断裂面上观察到规律性的条纹带形貌,疲劳条纹带的形成与裂纹尖端银纹区的产生具有一定的联系.表面直接氟化改性后疲劳条纹带扩展速率的降低也充分证明了有机玻璃疲劳寿命的提高.研究结果证明,表面直接氟化改性修复是一种提高有机玻璃疲劳性能的可行方法,对有机玻璃的工业使用具有指导意义.The direct fluorination, a convenient method developed for surface modification, was employed to improve the bending fatigue performance of Poly(methyl methacrylate)(PMMA). After the surface treatment by direct fluorination under certain conditions, the modification effect on the surface properties of PMMA was confirmed by x-ray photoelectron spectroscopy(XPS) and scanning electron microscopy(SEM). A smooth and densified fluorination layer being 5 microns thick was observed on the surface, showing the effectiveness of direct fluorination. The bulk material behaviors of PMMA such as the dynamic mechanical properties, fracture toughness and bending strength were also measured. The enhancement of these properties due to fluorination was insignificant since only a very thin layer of material was actually fluorinated. The three-point bending fatigue behaviors including the fatigue lifetime and fatigue crack propagation of PMMA with different types of pre-notches before and after the direct fluorination were comprehensively studied. The experimental results of the bending fatigue tests showed significant improvement in the fatigue performance of PMMA after the direct fluorination. This is believed to be owing to the structural constraining effect accompanying the formation of fluorinated surface layer in the bending samples of PMMA. Although the reduction of deflection after fluorination derived with the linear elastic bending theory in each bending cycle is not substantial, the cumulative influence on the fatigue performance of PMMA can be noticeable, especially during damage evolution. The propagation rate of fatigue striation decreased obviously after the direct fluorination, implying that the fluorination modification improves the bending fatigue performance of PMMA. The evolution of regular striation morphology on the fatigue fracture surface was also found to be correlated with the occurrence of craze at the crack tip. This work shows that the surface modification by direct fluorination is a feasible approach to

关 键 词：有机玻璃 表面直接氟化 断裂强度 疲劳寿命 疲劳裂纹扩展 

分 类 号：TQ317[化学工程—高聚物工业]