Strength prediction method for unidirectional GFRP after hydrothermal aging

This paper proposes a strength prediction method for unidirectional glass fiber reinforced plastics (GFRPs) after hydrothermal aging: immersion in deionized water at 80°C. First, the strength degradation of the constituents (i.e., the glass fiber and the fiber/matrix interface) of unidirectional GFRP after hydrothermal aging was evaluated from the fiber strength and the interfacial shear stress by using a single-fiber composite (SFC). Both the fiber strength and the interfacial shear stress had a tendency to decrease in the early stage of hydrothermal aging and to saturate toward certain values with long-term aging. In addition, the tensile strength of the unidirectional GFRP was measured after hydrothermal aging. The residual strength of the unidirectional GFRP also had a tendency to decrease sharply in the early stage of hydrothermal aging and to saturate toward a certain strength with long-term aging. Finally, the residual strength of the unidirectional GFRP after hydrothermal aging was predicted using the global loading sharing (GLS) model, by considering the degradation of both the glass fiber and the fiber/matrix interface. The predicted results indicated good agreement with the experimental data while considering not only the degradation of the fiber reinforcement but also the fiber/matrix interface adhesion. It was concluded that the GLS model applied considering the degradation of the GFRP constituents would be a suitable and a simple model to predict the residual strength of the unidirectional GFRP after hydrothermal aging.