Durability of Two Epoxy Adhesive BFRP Joints Dipped in Seawater under High Temperature Environment

Fiber-reinforced polymers (FRPs) have great potential in shipbuilding. As a new type of material, basalt-fiber-reinforced polymer (BFRP) has received increasing attention due to its good economic and environmental performance. In this paper, BFRP single-lap joints (SLJs) bonded by Araldite^®2011 and Araldite^®2014 were selected as sample objects, the joints, aged for 240 h, 480 h, and 720 h, were experimentally analyzed in 3.5% NaCl solution/5% NaCl solution at 80 °C. The sequential dual Fickian (SDF) model was used to fit the water absorption process of the dumbbell specimen material. By comparison, the water absorption of the material occurred mainly on the adhesive and the water absorption of Araldite^®2011 was higher than that of Araldite^®2014. The decrease in the T_g of the aged joint adhesive was characterized by DSC, and the TG test showed that the polymer material in the joint was degraded by the damp-heat effect. The quasi-static tensile test showed that the decrease in joint failure strength was positively correlated with the water content of the solution. The Araldite^®2011 adhesive joint showed better mechanical properties and stability than the Araldite^®2014 adhesive joint, while the secondary crosslinking of the bound water with the polymer chain resulted in a slight increase in the stiffness of the aged joint. From comprehensive observation of the macro-section and SEM-EDX images, it is concluded that the failure mode of the joint changes from fiber tearing to mixed failure of fiber tearing and adhesive layer cohesion, and the plasticizing effect of the epoxy resin in the adhesive and chemical corrosion of salt ions weakens the adhesive layer's bond strength.