Threshold Properties of Woven GFRP Laminates under Acid Environment

研究了玻璃纤维增强塑料（GFRP）的应力腐蚀开裂机理。首先，研究了组分对c -玻璃/乙烯基酯编织层合板断裂和裂纹扩展的阈值特性的影响。在HCl溶液、水和空气中对其繁殖行为进行了评价。结果，行为被绘制在da/dt-K_I图上。裂纹扩展速率da/dt分布在水中比在空气中显著增强，且与在HCl溶液中几乎相同。因此，研究了单向FRP的裂纹扩展特性，以确定纤维方向的作用。在da/dt-K_I图上显示了90°单向FRP的阈值特性，通过有限元分析确定了纤维桥接的原因。采用单纤维模型复合材料对界面降解机理进行了研究。在本研究中，降解是通过界面脱键能来描述的。测量了纤维破坏点附近的界面脱粘长度，计算了能量。同时测量了基体塑性区，因此在能量平衡模型中考虑了塑性来确定界面脱粘能。进一步表明，界面脱粘能保持恒定值。为了评估纤维和界面的断裂行为，采用了双解理钻孔压缩（DCDC）试验。并在试件中嵌入一根纤维束，以估计其断裂机制。裂纹在纤维束周围发生偏转，纤维/基体界面发生脱粘。结果表明，脱键长度与界面降解程度有关。脱粘长度和界面脱粘能决定裂纹表面的桥接应力。桥接应力决定了裂纹表面的牵引力，但牵引力会因纤维断裂而减小。最后讨论了牵引力对增韧效果的影响。少

The stress corrosion cracking mechanism of glass fiber reinforced plastics (GFRP) were investigated in this work. First of all, an effect of the constituents on the fracture and the threshold properties on the crack propagation of woven C-glass/vinyl ester laminates. The propagation behavior was evaluated in HCl solution, in water and in air. As a result, the behavior was plotted on the da/dt-K_I diagrams. The crack-propagation rate da/dt distribution in water was largely enhanced in comparison with that in the air, and it was nearly as promoted as that in the HCl solution. Therefore the crack-propagation properties of unidirectional FRP were investigated to confirm the role fiber direction. The threshold properties the 90° unidirectional FRP were appeared on the da/dt-K_I diagrams and the it is confirmed that the cause is the fiber bridging by the FEM analysis.Single fiber model composites were applied to evaluate the interfacial degradation mechanisms. The degradation was described b … More y interfacial debonding energies in this study. And the interfacial debond length near the fiber failure point was measured to calculate the energies. The matrix plastic zone was also measured, therefore the plasticity was considered in the energy balance model to decide the interfacial debonding energies. Furthermore it was suggested that the interfacial debonding energy kept the constant value.In order to estimate the fracture behaviors of the fiber and interface, the double cleavage drilled compression (DCDC) test was applied. And one fiber bundle was embedded in the specimen in order to estimate the fracture mechanisms. The crack was deflected around the fiber bundle and the fiber/matrix interface was debonded. As a result, it was found that the debond length depended on the interfacial degradation. The debonding length and interfacial debonding energy decided the bridging stress on the crack surface. And the bridging stress determined the traction on crack surface, although the traction decreased due to the fiber failure. Finally the toughening effect that depended on the traction was discussed. Less