Mechanical characterization and asymptotic homogenization of 3D-printed continuous carbon fiber-reinforced thermoplastic

The present work investigates the mechanical properties of continuous carbon fiber-reinforced thermoplastic by testing composite specimens which were manufactured using an innovative process based on the fused filament fabrication (FFF, analogous to FDM (R)). The adopted testing procedures and their results are presented, as well as an introduction to the manufacturing process, which is patented by Markforged Inc. The experimental mechanical properties (stiffness and strength) of the composite specimens, measured in tensile (longitudinal and transverse), compression (longitudinal) and in-plane shear are reported. The asymptotic homogenization technique is applied in order to predict the elastic mechanical properties of the carbon fiber-reinforced lamina. In contrast to recent studies, this investigation has revealed that considering Nylon as the thermoplastic matrix embedding the continuous fiber consistently underpredicts the transverse and in-plane shear elastic properties of the reinforced laminae. These results suggest that the composition of the thermoplastic resin is not exactly the same for the unreinforced and reinforced filaments. Additionally, cross-sectional micrographs of specimens are analyzed in detail and considerable insight has been gained concerning the thermoplastic resin of reinforced filaments.