Polylactic acid (PLA) is a biodegradable polymer that can replace petroleum-based polymers and is widely used in material extrusion additive manufacturing (AM). The reprocessing of PLA leads to a downcycling of its properties, so strategies are being sought to counteract this effect, such as blending with virgin material or creating nanocomposites. Thus, two sets of nanocomposites based respectively on virgin PLA and a blend of PLA and reprocessed PLA (rPLA) with the addition of 0, 3, and 7 wt% of titanium dioxide nanoparticles (TiO₂) were created via a double screw extruder system. All blends were used for material extrusion for 3D printing directly from pellets without difficulty. Scanning electron micrographs of fractured samples’ surfaces indicate that the nanoparticles gathered in agglomerations in some blends, which were well dispersed in the polymer matrix. The thermal stability and degree of crystallinity for every set of nanocomposites have a rising tendency with increasing nanoparticle concentration. The glass transition and melting temperatures of PLA/TiO₂ and PLA/rPLA/TiO₂ do not differ much. Tensile testing showed that although reprocessed material implies a detriment to the mechanical properties, in the specimens with 7% nano-TiO₂, this effect is counteracted, reaching values like those of virgin PLA.

Many studies assess the suitability of fiber-reinforced polymer composites in additive manufacturing. However, the influence of the fiber length distribution on the mechanical and functional properties of printed parts using these technologies has not been addressed so far. Hence, in this work we compare different composites based on Acrylonitrile Styrene Acrylate (ASA) and carbon fiber (CF) suitable for large format additive manufacturing (LFAM) technologies based on fused granular fabrication (FGF). We study in detail the influence of the CF size on the processing and final properties of these materials. Better reinforcements were achieved with longer CF, reaching Young’s modulus and tensile strength values of 7500 MPa and 75 MPa, respectively, for printed specimens. However, the longer CF also worsened the interlayer adhesion of ASA to a greater extent. The composites also exhibited electrical properties characteristic of electrostatic dissipative (ESD) materials (10⁵–10¹⁰ Ω/sq) and low coefficients of thermal expansion below 15 µm/m·°C. These properties are governed by the CF length distribution, so this variable may be used to tune these values. These composites are promising candidates for the design of elements with enhanced mechanical and functional properties for ESD protection elements or molds, so the products can be manufactured on demand.

In this study, olive pit agro-waste from the olive oil industry is valorized by incorporating it as an additive in a polyethylene terephthalate glycol (PETG) matrix to develop bio-based composite materials for large format additive manufacturing (LFAM). The olive pits were first ground into olive pit powder (OPP) and then functionalized by polymerizing poly(butylene adipate-co-terephthalate) PBAT on their surface, resulting in a hydrophobic, modified olive pit powder (MOPP) with enhanced compatibility with the PETG matrix. OPP and MOPP composites were compounded and 3D-printed via Fused Granular Fabrication (FGF) using 5, 10, and 15 wt.% concentrations. The PBAT coating increased the degradation temperature and specific heat capacity of the material, contributing to a lower melt viscosity during printing, as confirmed by MFR, MDSC, and TGA analyses. Tensile testing revealed that MOPP composites generally exhibited superior mechanical properties compared to OPP composites, likely due to the improved compatibility between PBAT on the MOPP surface and the PETG matrix. SEM analysis further validated these findings, showing a highly irregular and porous fracture surface in OPP composites, while MOPP composites displayed a smooth surface with well-integrated MOPP in the PETG matrix.

The development of 3D modeling tools has allowed the construction of geometries that were unattainable computationally until a few decades ago. Specifically, parametric design and modeling is gaining significant importance in the conceptualization of new designs and products. This communication shows some of the resulting prototypes, designed and manufactured by INNANOMAT research group (TEP 946) of Cadiz University. A product design methodology for Additive Manufacturing (AM) and functional luminaire models proposed in the scope of two projects: ADICORK and 3DBLEND. In these projects, bio-inspired texture designs were explored in natural elements and environments of the province of Cádiz, in order to highlight this region and the value of its ecosystem. In both projects, sustainable polymeric blends were developed that served as base material for the manufacture of part of the prototypes shown in this communication. For these designs, parametric design programs such as Grasshopper, a Rhinoceros plugin, were used to obtain complex models that achieve a unique and differentiating aesthetic. The result of the modeled texturing is combined with surfaces in Rhinoceros. Once the textured model is defined, it is detailed and finished in modeling programs where dimensional control is greater, and the design is adjusted to the specific AM technology chosen. In this case two were used, Fused Filament Fabrication (FFF) and Fused Granular Fabrication (FGF). Keywords: Parametric design; Fused Granular Fabrication; Additive Manufacturing; product design; Biomimicry

This work evaluates the influence of processing on the production of various cork composites. Cork agro-waste with different particle sizes, namely fine cork (FC, D_p < 250 µm) and coarse cork (CC, 1 mm < D_p < 2 mm), was valorized. It was possible to process composites containing up to 20 wt.% FC and 15 wt.% CC using a twin-screw extruder. These composites were subsequently manufactured via large-format additive manufacturing (LFAM) using fused granular fabrication (FGF). The effects of cork concentration and processing duration in the extruder on particle integration, as well as on the mechanical, physical, and thermal properties of the composites, were studied. As expected, a linear decrease in mechanical properties was observed with increasing cork content. For the same cork content and longer processing durations, properties were similar for FC and CC composites. Shorter processing durations in the extruder minimized degradation of FC. However, partial degradation occurred during FGF printing, leading to the formation of composite foams with increased porosity, lower density, and enhanced thermal insulation.