Study on Fatigue Fracture Mechanism of Short Glass Fiber Reinforced Plastic

通过单轴和多轴疲劳试验，研究了短玻璃纤维增强聚苯醚（GFPPE）、聚苯硫醚（GFPPS）、聚苯乙烯（GFSPS）和玻璃珠增强聚甲醛（GBPOM）的疲劳性能。研究发现，故障的循环次数与间隔时间的持续时间密切相关。在单轴疲劳试验中，间隔时间导致更大的失效循环次数。而在多轴疲劳试验中，间隔时间导致裂纹萌生和最终破坏的循环次数较少。通过声速测量和光学显微镜（OM）观察研究了其破坏机理。试验结果表明，不同加载方式（单轴加载方式和多轴加载方式）、加载间隔时间不同，损伤区发育机制不同，主要表现为玻璃纤维断裂、微空化、玻璃纤维取向改变和基体塑性变形。实验结果表明，损伤发展机制的差异是由于加载方式和间隔时间不同，对载荷的弹性响应不同，从而导致局部或非局部损伤积累。不同的损伤发展机制反过来影响载荷能量的吸收，从而导致不同的疲劳寿命

The fatigue properties of short glass-fiber reinforced polyphenyleneether (GFPPE), polyphenylenesulfide (GFPPS), syndiotactic polystyrene (GFSPS), and glass-bead reinforced polyoxymethylene (GBPOM) were studied through uni-axial and multi-axial fatigue tests. It was found that the numbers of cycles to failure were strongly dependent on the duration of the interval time. In the case of uni-axial fatigue tests, the interval time resulted in greater numbers of cycles to failure. In multi-axial fatigue tests, however, the interval time resulted in smaller numbers of cycles to crack initiation and ultimate failure. The failure mechanism was investigated through acoustic velocity measurements and optical microscope (OM) observations. The results of those measurements suggested that the different behaviors in fatigue tests under different conditions are attributable to the differences in mechanisms of damage zone development, which consisted with breakage of glass fibers, micro-voiding, changes in the orientation of glass fibers, and plastic deformation of matrix depending on the test conditions such as loading mode (uni-axial and multi-axial) and interval times between loading. Experimental results suggested that the difference in the damage development mechanisms were caused by the different elastic response to the loading resulting in the localized or delocalized damage accumulation depending on the loading mode and interval time. The different damage development mechanisms, in turn, affect the absorption of loading energy resulting in the different fatigue life