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

研究了酸性应力环境下玻璃钢层合板的裂纹扩展行为和门槛值性能。以E-玻璃纤维和环氧树脂为试件，研究了加载条件和环境条件对层合板在盐酸溶液中的裂纹扩展行为和门槛值的影响，并进行了恒定加载和循环加载试验，改变应力比和频率进行循环加载试验。结果表明，裂纹扩展依赖于时间和最大应力强度因子K&lt；lmax&gt；在K_&lt；lmax&gt；-da/dt图中没有出现循环加载加速裂纹扩展的现象。此外，还验证了两种加载条件下的门槛应力强度因子K&lt；ISCC&gt；在本研究范围内有显著差异。从断口观察，在循环加载条件下，纤维的界面断裂和拔出是显著的。至于环境条件，研究了盐酸溶液中酸浓度和温度的变化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，固溶温度为303K时，K_&lt；ISCC&gt；趋于恒定；在循环加载条件下，固溶温度为303K时，K_&lt；ISCC&gt；在lmoh/L处出现极小值。Arrhenius方程在裂纹扩展稳定的区域可根据Paris的功率低来采用。对于阈值特性，在恒定加载条件下，温度的影响很小。在循环加载和343K固溶条件下，K&lt；ISCC&gt；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.