Characteristics of Stress Corrosion Cracking in GFRP Laminates under Acid Stress Environment

酸应力环境下GFRP层合板裂纹扩展行为及阈值特性研究。研究了由e -玻璃纤维和环氧树脂制成的GF/环氧树脂试样，研究了加载条件和环境条件对HCI溶液中裂纹扩展行为和阈值特性的影响。进行了恒加载和循环加载试验，从而改变了循环加载试验的应力比和频率。结果表明，裂纹扩展依赖于时间和最大应力强度因子K_<lmax>。在K_<lmax>-da/dt图中，循环加载对裂纹扩展没有加速作用。进一步验证了两种加载条件下的阈值应力强度因子K_<ISCC>在我们的研究范围内存在显著差异。从断口学观察来看，在循环加载条件下，界面裂纹和纤维的拉拔是显著的。在环境条件下，研究了HCI溶液酸浓度和温度对裂纹扩展行为的影响。随着酸浓度的增加，在恒定加载条件下，溶液温度为303K时，K_<ISCC>趋于恒定。在循环加载条件下，溶液温度为303K时，K_<ISCC>在lmoh/l时达到最小值。固溶温度的升高导致裂纹扩展速度加快。在稳定裂纹扩展区域，根据Paris的功率低，可以采用Arrhenius方程。在恒加载条件下，温度对阈值性能的影响较小。另一方面，在循环加载条件和溶液温度为343K时，K_<ISCC>减小，最小值消失。

Studies on crack propagation behaviors and threshold properties of GFRP Laminates under an acid stress environment.GF/epoxy specimens, which are made of E-glass fiber and epoxy resin, are investigated, and effects of the loading conditions arid the environmental conditions on crack propagation behaviors and threshold properties in HCI solution are researched.Constant and cyclic loading tests are performed, so that the stress ratio and the frequency are changed for the cyclic loading tests. As a result, it is found that crack propagation depends on a time and the maximum stress intensity factor, K_<lmax>. There is no acceleration of crack propagation due to cyclic loading in a K_<lmax>-da/dt diagram. Furthermore, it is verified that the threshold stress intensity factors, K_<ISCC>, under both loading condition have a distinguished difference in the range of our study. From fractographic observations, interfacial crackings and pull-outs of fibers are remarkable under the cyclic loading condition.As for the environment condition, changes in the crack propagation behaviors due to the alternations of acid concentration and temperature of the HCI solution are researched. As the acid concentration increases, the K_<ISCC> seems to be a constant under the constant loading conditions and the solution temperature of 303K.And it is noted that the K_<ISCC> takes its minimum value at lmoh/l under the cyclic loading conditions and the solution temperature of 303K.Increase of the solution temperature lead to the quickening of crack propagation. Arrhenius' equation can be adopted in a stable crack propagation region according to Paris' power low. As for the threshold properties, there is little effect of temperature under the constant loading conditions. On the other hand, the K_<ISCC> decreases and its minimum value vanished under the cyclic loading conditions and the solution temperature of 343K.