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Fused deposition modeling (FDM), which is a popular and widely additive manufacturing technique, opens alternative possibilities for complex geometries that are hard to manufacture using classic manufacturing techniques. Its use in functional products is however limited because of anisotropic strength issues, where the strength of FDM-fabricated parts in the build direction (Z direction) can be significantly lower than in the X-Y directions. This work aims at addressing this particular point for a not-well-known polymer, namely acrylonitrile styrene acrylate or ASA. Using central composite design and response surface methodology, the nozzle temperature (A), printing speed (B), and layer thickness (C) were studied in a systematic manner to evaluate their effects on the Z-direction tensile properties of 3D-printed ASA's samples. Analysis of variance results demonstrate that layer thickness is the most influential printing parameter on interlayers bonding. The best tensile properties for 3Dprinted ASA parts were achieved with parts produced at A = 270[degrees]C, B = 60 mm [s.sup.-1], and C = 0.155 mm. Scanning electron microscopy observation confirms that printing ASA material with those optimum parameters clearly improves the interlayers' bonding in the build direction. KEYWORDS ASA, fused deposition modeling, layers' adhesion, tensile properties, 1 | INTRODUCTION Additive manufacturing (AM) is a revolutionary technique that enables the fabrication of 3D-printed parts with different structures and various properties. [1] This technique offers many technologies, and [...]

Many parameters of fused deposition modeling (FDM) influence the resulting mechanical properties. This can become a key factor if those parts are intended for commercial applications. This study focuses on the influence of nozzle temperature and infill line orientations for parts made with short carbon fiber (CF)-reinforced polylactic acid (PLA). Tests bars made of PLA and PLA-CF composite were produced under carefully selected conditions. As expected, PLA-CF yields higher tensile properties compared to PLA, owing to the strengthening effect of high modulus CFs. Maximum tensile properties are attained for a nozzle temperature of 230°C, for both PLA and PLA-CF. This temperature was thus selected for probing the effects of infill orientations in test bars. Among the multiple orientations tested, the combination [0°, 15°, −15°] relative to the long axis of the test bar yields the highest levels of tensile properties for both PLA and PLA-CF over the "all-purpose" [45°, 135°] orientation. Annealing can also affect crystallinity and mechanical properties of manufactured parts. Through differential scanning calorimetric analyses, the degree of crystallinity was assessed for samples annealed under various conditions. Results show that annealing increases crystallinity in PLA and PLA-CF samples, with a lower cooling rate yielding higher values. The Young's modulus exhibits the same behavior for annealed and as printed parts, with a lower cooling rate yielding higher modulus values. This is attributed to a relaxation of the material structure as well as to the orientation of polymer chains toward the CFs. [ABSTRACT FROM AUTHOR]