Threshold Properties of Woven GFRP Laminates under Acid Environment

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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