Material extrusion additive manufacturing (MEAM), a sub-branch of three-dimensional (3D) printing is growing in popularity. Test specimens were 3D-printed using commercial polylactic acid (PLA) filament, and PLA filament reinforced with short-carbon fibers (PLA/CF). As-printed specimens and specimens that were annealed at three different temperatures, then subjected to tensile testing. The internal microstructures of the samples were also examined. The effects of the short-carbon fiber fillers on the mechanical properties of 3D-printed PLA were investigated, and the effects of the annealing process on polymer crystallinity and mechanical properties. The annealing process was shown to increase the crystallinity of both sample groups, though no statistically significant effect of annealing on mechanical properties was observed. The tensile properties of the PLA and PLA/CF filaments showed that the addition of carbon fibers to the PLA filament led to a significant increase in elastic modulus of the MEAM samples.

Extrusion-based additive manufacturing (EBAM) or 3D printing is used to produce customized prototyped parts. The majority of the polymers used with EBAM show moisture sensitivity. However, moisture effects become more pronounced in polymers used for critical applications, such as biomedical stents, sensors, and actuators. The effects of moisture on the manufacturing process and the long-term performance of Shape Memory Polyurethane (SMPU) have not been fully investigated in the literature. This study focuses primarily on block-copolymer SMPUs that have two different hard/soft (h/s) segment ratios. It investigates the effect of moisture on the various properties via studying: (i) the effect of moisture trapping within these polymers and the consequences when manufacturing; (ii) and the effect on end product performance of plasticization by moisture. Results indicate that higher h/s SMPU shows higher microphase separation, which leads to an increase of moisture trapping within the polymer. Understanding moisture trapping is critical for EBAM parts due to an increase in void content and a decrease in printing quality. The results also indicate a stronger plasticizing effect on polymers with lower h/s ratio but with a more forgiving printing behavior compared to the higher h/s ratio.

Nanocomposite technologies can be significantly enhanced through a careful exploration of the effects of agglomerates on mechanical properties. Existing models are either overly simplified (e.g., neglect agglomeration effects) or often require a significant amount of computational resources. In this study, a novel continuum-based model with a statistical approach was developed. The model is based on a modified three-phase Mori–Tanaka model, which accounts for the filler, agglomerate, and matrix regions. Fillers are randomly dispersed in a defined space to predict agglomeration tendency. The proposed model demonstrates good agreement with the experimentally measured elastic moduli of spin-coated cellulose nanocrystal reinforced polyamide-6 films. The techniques and methodologies presented in the study are sufficiently general in that they can be extended to the analyses of various types of polymeric nanocomposite systems.

This study aims to assess the effect of printing parameters on the final tensile properties of 3D printed specimens printed through a popular vat-photopolymerization printer—‘Form 2’. Elastic modulus, ultimate tensile strength and strain at break are analyzed as a function of process parameters in order to provide an optimized print parameter configuration. Design of Experiments (DoE) using Taguchi’s techniques was used to print the test samples. Tensile tests were performed on the 3D printed specimens following the ISO-527 standard. The post-experiment analysis provide more insight on the effect of each studied factor on the elastic properties of these specimens. To complete this study, an analysis of the total manufacturing process time is presented with respect to the aforementioned elastic properties. The study shows that the parts are orthotropic and sensitive to layer height and post-curing. The orthotropic behaviour can be substantially reduced by appropriate post-curing process, resulting in high improvement of the elastic modulus and ultimate tensile strength. This paper is of special interest to researchers and users of desktop 3D printers who wish to improve the performance of their equipment, compare printing capabilities or assess the effect of different hardware on a single resin.