Time Dependent Characteristics and Long-term Reliability of PMC in Hostile Environment

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Polymer matrix composites(PMC) such as Fiber Reinforced Plastics(FRP) have numerous variations in its components, and therefore it is possible to design its mechanical properties corresponding to its application. Previous researches dealing long-term reliability of FRP in corrosive environment mostly focus on macroscopic damage failure such as crack propagation and mechanical properties degradation, but not on its failure mechanism. The failure of FRP occurs from the accumulation of microscopic damage in its components. Thus present research focus on microscopic damage such as degradation in mechanical properties of resin matrix, strength degradation of fiber reinforcement, and interfacial degradation, and furthermore, evaluated these degradation behavior quantitively.Firstly, neat matrix resin specimen was immersed in Deionized water and was statically〜in air to measure its mechanical properties such as stiffness and rupture strain. The stiffness remained unchanged but the rupture str … More ain increased in vicinity of immersion.Secondly, E-glass fiber was embedded in the epoxy resin to mold Single Fiber Composite(SFC) specimen. Constant strain test of SFC specimen was conducted under water environment(40, 75[℃]. Fragmentation test was conducted after the constant strain test to estimate fiber residual strength. It was clarified that the fiber strength degrades by constant strain test, and the degradation accelerates with higher applied strain, immersion time, and higher water temperature. Furthermore subcritical crack growth model was applied to predict the fiber strength degradation.Finally, the length of interfacial debonding accompanied with embedded fiber failure was measured to estimate the maximum shear strength. Also, from the energy balance in vicinity of fiber failure, Energy Release Rate(ERR) was quantified. Wagner's model and Morais's model were applied to estimate maximum shear strength and ERR. It was clarified that both values degrades and showed a tendency to saturation. Less