Abstract
This study aims at numerically investigating the effects of the mechanical properties of thermoplastic resin (TP) on fracture mode and welding strength in the welding technology of thermoset FRP which makes use of a carbon fiber (CF) and a thermoset resin (TS) matrix. This welding structure has a complex-shaped interface between the TS and TP, and in this study, the TP parameters considered are: TP/CF interfacial strength, TP yield stress, fracture energy at the TP/CF interface and TP Young’s modulus. We employ a finite element method and use three models with different fiber arrangement. The simulation results indicate that TP ductile fracture occurs when TP yield stress is low, and that interfacial debonding at the TP/CF or TS/CF interface occurs when the yield stress becomes high enough, regardless of fiber arrangement. The results also reveal that CFs arrest crack propagation induced by TS/TP interfacial debonding and prevent the structure from experiencing final fracture. Additionally, mechanical properties of TP governs the fracture modes, which affect welding strength. As TP/CF interfacial debonding occurred, the welding strength is predominantly determined by TP/CF interfacial strength and is hardly affected by fiber arrangement. Additionally, it saturates by the fracture mode transition to TS/CF interfacial debonding and increases as TP Young’s modulus or fracture energy at the TP/CF interface increases. These results suggest that a suitable TP can increase welding strength in the welding technology of thermoset FRP.
