Abstract3D printing plays an important role in Industry 4.0 and has versatility to use different materials, including thermoplastic polymers. Polylactic acid (PLA), a bio‐based biodegradable polymer, is used as a potential replacement for petroleum‐based polymers in several applications, and is one of the most popular polymers used in 3D printing. Inorganic/organic nanoparticles can be incorporated in polymers to improve various properties such as thermal, mechanical, and tribological. This work investigates the effect of adding carbon black (CB) and alumina (ALM) nanofillers on the thermal, mechanical, and tribological properties of 3D printed PLA nanocomposites for tribological applications. Both nanofillers promoted progressive enhancement of thermal stability according to TGA. The improvement in the interaction between nanofillers and PLA matrix is revealed by an increase in viscosity of the nanocomposites. The nanocomposites containing 25%wt ALM and 75wt% CB presented better mechanical and wear properties, suggesting synergism between nanofillers and that CB may act as a compatibilizer between PLA and ALM. These results enable selecting the most suitable composition of nanofillers to be added to PLA to create filaments with better tribological properties.

Fused deposition modeling (FDM) is a rapidly growing additive manufacturing technology due to its ability to manufacture complex‐shaped parts in a simple process. FDM parts present inherent porosity due to the fabrication process. The mechanical performance of the built part depends on controlling several printing parameters of the specimen and the quantity of voids. PLA/PBAT [polylactic acid/poly(butylene adipate‐co‐terephthalate)] blend is a biodegradable polyester with bio‐based content that is used as a potential replacement for conventional petroleum‐based polymers. PBAT reduces the stiffness and improves the tear strength of PLA. There is a lack of research on PLA/PBAT 3D printed parts, especially the relationship between flexural mechanical properties and porosity of PLA/PBAT parts. The aim of this work is to investigate the effect of layer thickness (LT), deposition speed (DS), and printing direction (PD) on porosity and flexural properties of PLA/PBAT blend parts. Experimental design method is used to identify the set of parameters, which gives optimized results. Specimens fabricated with lower printing parameter values allowed obtaining parts with less porosity and consequently improved bending properties.

Summary: The use of lignocellulosic fibers as reinforcement in polymer composites has increased worldwide recently. Vegetal fibers have low cost and they are commonly available in Brazil. The curaua fibers in particular are of great importance for the development of the Amazon region. The mechanical behavior of the composites reinforced with fibers depends on the effectiveness of the transfer of the applied load by the matrix to the fibers, which is determined by the magnitude of the interfacial bonding between fiber/matrix phases. In this paper, curaua fibers were treated with 0.25-2% (w/v) NaOH solution under tensile loading to improve fiber-matrix adhesion in curaua fibers/epoxy laminates. Composites with 40 vol.% curaua fibers were obtained. Maximum improvement in the composite properties was observed for those containing curaua fibers treated with 0.5% NaOH under tensile loading. Composites with good bending properties were obtained by using a simple, low cost and environmental friendly method for curaua treatment. This method employed low concentration of chemical solutions, which are neutralized during the process, and no need of heating.

In additive manufacturing, determining the correct deposition parameters is very important as this can affect the final properties of printed parts. Since there is no agreement on the optimal level of the different printing parameters in reported results, this work evaluated the influences of layer thickness (LT), deposition speed (DS) and printing direction (PD) on tensile properties and dimensional accuracy of poly(lactic acid) 3D parts evaluating the possibility of using thin plate spline interpolation method (TPSIM) of data, a new approach, in determination of optimized fused deposition modeling process parameters. It was observed that the use of low levels of LT (0.10 mm), DS (40 mm/s), and PD (0°) provided parts with higher mechanical strength and dimensional performance. Denser parts showed lower anisotropy effect and, consequently, best tensile properties were obtained. TPSIM was an efficient mathematical analysis and well fitted results of predicted and experimental results.