Fused filament fabrication (FFF) has been used to create prototypes and functional parts for various applications using plastic filaments. It has also been extended to the use of continuous fibers for reinforcing thermoplastic polymers. This study aims to optimize the deposition design of a coextruded continuous carbon fiber (CCF) composite filament with a polyethylene terephthalate glycol‐modified (PETG) filament. The characterizations on the raw materials revealed that the matrix polymer in CCF composite filament had similar physicochemical properties as PETG, and carbon fibers were homogeneously distributed in CCF filament. The effect of raster orientation and shells number on the mechanical properties of non‐reinforced and coextruded CCF‐reinforced PETG was investigated. The highest mechanical properties were obtained at a raster orientation of 0° for both reinforced and non‐reinforced materials. With the increase of raster orientation, Young's modulus and ultimate tensile strength decreased. The presence of shells improved the tensile strength of non‐reinforced PETG. For composite samples printed with unreinforced shells, Young's modulus decreased due to decrease in fibers content, and elongation at break and ultimate tensile strength increased. Tomographic observations showed that the mechanical behavior of printed specimens depended on the anisotropy of porosity in printed specimens.

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This study aimed at assessing and optimizing the influence of printing speed and extrusion temperature in a fused filament fabrication (FFF) process on the tensile properties of a polylactide/layered silicate nanocomposite. Mathematical models using Doehlert designs were formulated to examine factor and interaction effects. The models were corroborated by measurements using capillary rheology, tomographic images, and crystallinity analyses to find physical explanations for the differences in tensile properties. The tensile properties were a non-monotonic function of printing speed, which may be due to various deposition defects that influence the porosity of composite tensile specimens. This study provides new insights into FFF process optimization regarding rheological behavior and mesostructure of nanocomposite by highlighting new modes of deposition defects that originate from process parameter settings and materials. The results contribute to the properties mastery of FFF-processed materials.

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Purpose The purpose of this study is to test a flexible polymer with different characteristics compared to other classical polymers mostly used in the additive manufacturing process, and to improve its mechanical properties and microstructure, by modifying different printing parameters, to make it more suitable for various industrial applications. Design/methodology/approach Seven parameters were tested, namely, nozzle temperature, bed temperature, layer thickness, printing speed, flow rate, printing time gap between two successive printed layers and raster orientation. Rheological characterizations were conducted to evaluate the influence of nozzle temperature on the melt viscosity of thermoplastic polyurethane (TPU). The effect of thermal printing parameters on the crystallinity behavior was explored. Tomographic characterizations were realized to measure the porosity and evaluate the internal structure quality of printed specimens. Findings Increases of the nozzle temperature, bed temperature, layer thickness and flow rate had a positive influence on the tensile strength properties of TPU with a reduction of porosity. Higher printing speeds created defects and negatively influenced the strength properties of TPU. An increase in the printing time gap between layers led to poor interlayer adhesion and decreased the tensile strength. Specimens with layers all oriented parallel to the loading direction exhibited superior mechanical properties compared to other raster orientations. Originality/value Thermoplastic elastomers are a unique class of polymers characterized by the combined thermal, chemical and mechanical properties of their elastomer and thermoplastic parts. TPU elastomer, as one of the elastomer families, has found an important position in the bioengineering and three-dimensional printing industry. This study reports a comprehensive study of the impact of additive manufacturing parameters on the properties of TPU.

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