玻璃纤维毡增强复合材料的低周拉伸疲劳性能研究

INVESTIGATION ON LOW CYCLE TENSILE FATIGUE PROPERTIES OF GLASS FIBER MAT REINFORCED COMPOSITES

采用玻璃纤维毡和不饱和树脂使用手糊成型的方法制作复合材料,并进行拉伸测试和低周疲劳测试来研究无孔和开孔玻璃纤维毡复合材料的拉伸性能。结果表明,试样的拉伸强度都随着纤维体积含量的增加而增加。在低周疲劳测试中,无孔和开孔试样的拉伸性能在55%载荷水平的低周疲劳作用下基本保持不变,但是在70%以上载荷水平的低周疲劳作用下发生了显著下降。对试样的断裂行为进行了研究,无孔试样拉伸断裂后有分层现象,开孔试样的断裂区域可以分为两个部分,分别为平行区域和扇形区域。特征长度通过使用有限元软件(MSC-Marc)计算出来,和测量出来的平行区域长度很接近,并且随着施加疲劳载荷水平的提高而降低,材料对孔洞的抵抗性降低。最后,对低周疲劳前后的破坏试样进行了扫描电镜观察以比较两者的不同。

In this paper,glass fiber mat and unsaturated polyester were used to fabricate composite through hand lay-up method. The tensile properties of unnotched and open-hole notched glass fiber mat reinforced composites（ GMC） specimens were examined based on the normal and low cycle fatigue（ LCF） tensile tests. It was found that both the unnotched strength and notched strength were promoted with increasing volume fraction（ Vf）. In LCF test,for unnotched and notched specimens,the properties of GMC showed stable in 30 cycles under 55% of max load but degraded much under the cycle load more than 70% of max load. In the investigation on the fracture behavior of specimens,delamination was found in the fracture section of unnotched test specimens. While for notched specimens,two different fracture areas defined as parallel area and fan shape area were found. The values of characteristic distance were calculated by finite element analysis software（ MSC-Marc）. Furthermore,the characteristic distance was found. It is close to the length of parallel area,decreasing with the increase of the load level in LCF tests,reducing the resistance of GMC to the effect from an open hole. Finally,SEM observation was carried out on the selected specimens to compare the difference between the ones before and after LCF test.