Effect of Fiber Hybrid Mode on Water Diffusion Behavior and Long‐Term Interfacial Performance of C/ GFRP Hybrid Rods

ABSTRACT

The use of fiber hybridization offers an effective means for achieving low cost, high strength, and superior durability for fiber‐reinforced polymer (FRP). However, the relationship between fiber hybrid mode and water diffusion behavior as well as interfacial performance remains unclear. In the present study, the effect of fiber hybrid mode on water absorption behavior of carbon and glass fiber‐reinforced polymer (C/GFRP) hybrid rods is obtained, and the quantitative contribution of water molecules to the reduction of interfacial shear strength (ISS) is determined. A long‐term ISS life prediction model is established based on the diffusion theory for three typical service conditions. The results reveal that water absorption of hybrid rods follows Fick's diffusion behavior. Large diameter glass fibers increase the diffusion path for water molecules, whereas high temperature (80°C) leads to resin matrix relaxation and interfacial debonding, thereby providing more diffusion space for water. The random hybrid (UDH) rod has lower water absorption than the coated hybrid (GCH, CGH) rods, because the random arrangement of carbon and glass fibers disrupts the diffusion of water molecules and thus extends their diffusion path. Higher temperature dramatically enhances hygrothermal stress at the glass fiber–resin interface, which in turn causes remarkable ISS deterioration at 80°C. The prediction results show that ISS decreases sharply at first and then slowly approaches a stable retention as water absorption becomes saturated. The corresponding stable retentions for carbon–resin, glass–resin, and hybrid carbon/glass–resin interfaces are 72.33%, 43.69%, and 48.68%, respectively.