Direct-joining of short carbon fiber-reinforced polyamide 6 composite with wood by additive manufacturing

Abstract The growing demand for sustainable lightweight materials in the transportation sector has intensified the search for new hybrid structures. This study investigates the joining of short carbon fiber-reinforced polyamide 6 composite (PA6-15CF) to European beech wood using an innovative additive manufacturing technique based on fused filament fabrication (FFF), known as AddJoining. Single-lap hybrid joints were fabricated by directly printing the polymer composite onto the natural wood substrate, achieving an ultimate lap-shear strength (ULSS) of 7.5 ± 1.2 MPa. Micromechanical interlocking and interfacial adhesion contributed to the robustness of the polymer-wood interface, as confirmed by microstructural analysis (OM and SEM) and FTIR spectroscopy, respectively. Fractographic analysis revealed a combination of adhesive and cohesive failure modes, with wood fibers embedded within the polymer matrix, indicating good interfacial compatibility. Furthermore, the joints exhibited remarkable mechanical durability under fatigue testing, achieving a fatigue life of 35% of the ultimate lap-shear force (ULSF) for 10 6 cycles, as estimated by the Weibull distribution with a reliability of 99%. The results demonstrate that AddJoining is a promising manufacturing strategy for producing lightweight, polymer-wood hybrid joints with potential application in sustainable structural design. Graphical abstract