Crack Progress Behavior of Woven GFRP Laminates under acid stress environment

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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.