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In this present study, the fused deposition modeling (FDM) method was used to fabricate the composites. Before three-dimensional (3D) printing, samples were designed according to the ASTM D256, D790 and D3039 standards for impact, flexural and tensile tests, respectively, using Onshape software before conversion to an STL file format. Afterward, the digital file was sliced with infill densities of 60%, 80%, and 100%. The composite samples contained chopped carbon fiber (cCF) and poly lactic acid (PLA), as reinforcement and matrix, respectively. The cCF/PLA (simply called cCFP) filaments were printed into various cCFP composite (cCFPC) samples, using a Viper Share bot 3D machine with different infill densities before the aforementioned mechanical testing. The tensile strength of cCFP were obtained as 25.9MPa, 26.9MPa and 34.75MPa for 60%, 80% and 100% infill density cCFP samples, respectively. Similarly, the flexural strength of cCFP were obtained as 11.8MPa, 12.55MPa and 18.4MPa and impact strength was 47.48kJ/m2, 48.45kJ/m2 and 48.96kJ/m2 for 60%, 80% and 100% infill density cCFP samples, respectively. The fractured/tested samples were examined and analyzed under a scanning electron microscope (SEM) to investigate the presence of fiber and void in the tensile sample. Based on the experimental results, it was evident that a high infill density of 100% with the highest reinforcement exhibited maximum impact strength, tensile and flexural strengths and moduli when compared with other lower carbon content of cCFPC samples. Therefore, the optimal 3D-printed cCFPC sample could be used for engineering application to benefit from properties of the polymer matrix composite materials and possibilities through additive manufacturing (AM). [ABSTRACT FROM AUTHOR]

The surface topography and interface characteristics play a significant role in determining the mechanical properties of carbon fiber reinforced polymer (CFRP) composites. These features are primarily influenced by the surface chemical structures and their interactions with the matrix resin. Here, we developed a rigid-flexible coating consisting of polyetheramine (PEA) and polydopamine (PDA) on the fiber surface to control the interface and improve the mechanical properties of CFRPs. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrum (FT-IR) results validated the successful introduction of polymeric chains and fiber surface characteristics including rough surfaces, slim polymer layers and uniform dots were examined by scanning electron microscope (SEM) and transmission electron microscopy (TEM). Contact angle tests indicate that the functionalized coating noticeably enhances the interaction force between carbon fibers, promoting improved wettability by the matrix resin. The bending and interlaminar shear strength of CFRP prepared by functional carbon fiber are increased by 45.76 % and 47.63 %, respectively. The drop weight impact (DWI) test confirms the positive effect of improved interfacial properties on the out-of-plane impact resistance of CFRPs. [Display omitted] [ABSTRACT FROM AUTHOR]