Crack Progress Behavior of Woven GFRP Laminates under acid stress environment

本研究的目的是阐明耐腐蚀GFRP复合材料在不同酸应力环境下的裂纹扩展、成分对断裂的影响以及C/VE和E/VE体系中裂纹扩展的阈值。进行了应力腐蚀开裂（SCC）试验和单纤维断裂试验。在HCl溶液、H_2SO_4溶液、水和空气中进行了恒载SCC试验，并用da/dt-K_1图描述了裂纹扩展行为。与空气中相比，水中的裂纹扩展行为大大增强，并且几乎与酸溶液中的裂纹扩展行为相同。酸应力环境下C/VE的破坏机制与腐蚀玻璃纤维的E/VE不同。正如预期的那样，主要原因是界面强度降低和基体吸水。采用单纤维E-glass/Vinylestr模型复合材料进行了单纤维破碎试验，研究了单纤维的降解机理。制备了受水和酸环境侵蚀的应力和非应力试样。研究了树脂中扩散现象对纤维强度和界面抗剪强度随浸泡时间的变化规律。结果表明，受应力试样的纤维强度低于无应力试样。结果表明，受应力的聚合物使腐蚀溶液的扩散速度加快。在不同的环境条件下，如水和酸，纤维的降解行为都没有改变。似乎只有水会扩散到树脂中，而酸不会。菲克氏扩散分析表明，在酸扩散开始时，纤维周围的水分浓度已经达到饱和极限。

The objective of this study is to clarify the crack-propagation of the corrosion-resistant GFRP that laminates under various acid stress environments, an effect of the constituents on fracture and the threshold of the crack propagation in the C/VE and E/VE systems. Two kinds of experiments of the stress corrosion cracking (SCC) test and the single fiber fragmentation test were performed.SCC tests were performed under constant loading in an HCl solution, H_2SO_4 solution, water and air, and the crack-propagation behavior was depicted on the da/dt-K_1 diagram. The crack-propagation behavior in water was largely enhanced in comparison with that in the air and it was almost as promoted as that in the acid solution. The failure mechanism of C/VE under the acid stress environment differed from E/VE with which the glass fiber was corroded. As expected, the main causes were the interfacial strength decrease and the water absorption of the matrix.Single fiber fragmentation tests were conducted to examine the degradation mechanism using a single fiber E-glass/Vinylestr model composite. Stressed and unstressed specimens under the environmental attack by water and acid were prepared. The effect of diffusion phenomenon into the resin on the fiber strength and the interfacial shear strength were investigated as a function of immersion time. As a result, the strength of fiber in stressed specimens was lower than that in unstressed specimens. This result indicates that the stressed polymer have the diffusion of the corrosive solution acceralated. The fiber degradation behavior was not changed regardless of each environmental condition, such as water and acid. It seemed that only the water would diffuse into the resin, and the acid would not. A Fickian diffusion analysis has shown that the moisture concentration around the fiber already reached a saturation limit at the beginning the acid diffusion.