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Weak mechanical strength and serious mechanical anisotropy are two key limiting factors for three‐dimensional (3D) parts prepared by fused deposition modeling (FDM) in industrial applications. In this work, we investigated the relationships between mechanical properties and surface quality of FDM parts with the properties of materials used. Three kinds of polylactide (PLA) filaments, composed of the same PLA matrix but different fillers (carbon fibers and talc), were used to prepare FDM specimens. Due to the nature of FDM process, FDM parts exhibited tensile properties weaker and more anisotropic than their injection‐molding counterparts. The presence of fillers affected the tensile properties of FDM parts, especially the degree of mechanical anisotropy. It is found that the interlayer bond governing the mechanical performance of FDM parts was improved since the fillers added in the polymer materials facilitates the molecular diffusion across the bond interface. Also, the surface quality of FDM parts varied with fillers. Neat PLA parts exhibited surface quality superior to the 3D parts printed with composites filaments. This work is believed to provide highlights on the development of polymer composites filament and improvement of mechanical properties of FDM parts. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47824.

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In the past decade extensive studies have been focused on mechanical properties of inorganic nanofiller/epoxy matrices. In this work we systematically investigated the mechanical properties of nano-alumina-filled E-54/4, 4-diaminodiphenylsulphone (DDS) epoxy resins, which were prepared via combining high-speed mixing with three-roll milling. Homogeneous dispersion of nano-alumina with small agglomerates was obtained in epoxy resin, which was confirmed using transmission electron microscopy (TEM). The static/dynamic modulus, tensile strength and fracture toughness of the nanocomposites were found to be simultaneously enhanced with addition of nano-alumina fillers. About 50% and 80% increases of K(IC) and G(IC) were achieved in nanocomposite filled with 18.4 wt% alumina nanofillers, as compared to that of the unfilled epoxy resin. Furthermore, the corresponding fracture surfaces of tensile and compact tension samples were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques in order to identify the relevant fracture mechanisms involved. Various fracture features including cavities/debonding of nanofiller, local plastic deformation as well as crack pinning/deflection were found to be operative in the presence of nano-alumina fillers.

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