Experimental and numerical evaluation of the interfacial adhesion properties of additively manufactured carbon-fiber-reinforced thermoplastic/64 titanium hybrids

This study presents an integrated numerical–experimental approach to analyze the interfacial fracture behavior of carbon fiber-reinforced thermoplastic (CFRTP)/metal hybrid joints. A two-scale damage analysis framework is proposed, combining finite element analysis (FEA) for macroscopic stress evaluation with a micromechanics model incorporating Christensen's failure criterion. This methodology enables visualization of the fracture process zone (FPZ) and quantitative assessment of interfacial damage evolution. To validate the approach, hybrid joints consisting of short-fiber CFRTP (sCFRTP), continuous-fiber CFRTP (cCFRTP), and 64Ti substrates were fabricated using a modified fused filament fabrication process. A polyimide film was inserted between the sCFRTP and 64Ti substrate to introduce an artificial precrack, which promoted stress localization during lap-shear testing. The joints demonstrated a maximum shear strength of 22.3 ± 0.3 MPa, with fractographic analysis revealing cohesive failure within the sCFRTP layer. These results suggest that the primary bonding mechanism is mechanical interlocking due to melt infiltration into the sandblasted titanium surface. The two-scale simulation revealed an FPZ extending approximately 27 μm along the interface, in agreement with the observed fracture morphology near the precrack tip. This framework offers a predictive tool for understanding damage propagation in dissimilar-material joints and holds promise for the design of lightweight, high-strength CFRTP–metal hybrid structures in advanced manufacturing applications. • Bonded CFRTP to 64Ti substrate via modified FFF process. • Estimate the fracture process zone by combining FEA and micromechanics model. • Resin damage began at 17 MPa; FPZ grew to 27 μm at 22.3 MPa near precrack tip.