Effects of printing patterns and fibre on the mechanical properties of additively manufactured carbon fibre reinforced polymer (CFRP)

This paper investigated the common mechanical properties of additively manufactured (AM) carbon fibre reinforced polymer (CFRP) composites using fused filament fabrication (FFF) for discontinuous-CFRP and continuous fiber fabrication (CFF) for continuous-CFRP. The aim was to understand how infill patterns and fibre natures (continuous and discontinuous) influenced the strength, stiffness, and toughness of the CFRP. The results of the study showed that the tensile and flexural strengths were strongly correlated with material content and structural reinforcement. The solid infill pattern clearly demonstrates the improve in mechanical properties compared to the other infill patterns. Discontinuous-CFRP significantly improved the strength (up to 76.77 MPa of tensile strength) and stiffness (up to 517.47 MPa of Young’s modulus). In contrast, continuous CFRP specimens displayed unexpectedly low strength (up to 10.5 MPa of tensile strength) and stiffness (up to 345.70 MPa of Young’s modulus), but remarkably high displacement (up to 20 mm) and deflection (up to 25 mm), indicating a highly ductile failure mode. The underlying mechanism was the matrix-fibre interface and load transfer during tensile and bending tests. Impact testing revealed a reversal in performance trends as continuous CFRP specimens (1.4 J) outperformed all others (about 0.9 J) in energy absorption, while the stiffest discontinuous CFRP specimens exhibits brittle fracture. This study highlights the trade-offs between strength, stiffness, and toughness in CFRP additive manufacturing, and demonstrates how thoughtful parameter selection can optimize mechanical behaviours, depending on their respective application requirements.