This paper introduces a methodology to study the anisotropic elastic constants of technical phenylene polysulfide thermoplastic (PPS), printed using fused deposition modeling (FDM) in order to provide designers with a guide to achieve the required mechanical properties in a printed part. The properties given by the manufacturer are usually taken from injected samples and these are not the real properties for printed parts. Compared to other plastic materials, PPS offers higher mechanical and thermal resistance, lower moisture absorption, higher dimensional stability, is highly resistant to chemical attacks and environmental aging, and its fireproof performance is good. One of the main difficulties presented when calculating and designing for FDM printing is that printed parts present anisotropic behavior i.e., they do not have the same properties in different directions. Haltera-type samples were printed in the three manufacturing directions according to optimum parameters for material printing, aimed at calculating the anisotropic matrix of the material. The samples were tested in order to meet standards and values for elastic modulus, shear modulus and tensile strength were obtained, using Digital Image Correlation System to measure the deformations. An approximated transversally isotropic matrix was defined using the obtained values. The fracture was analyzed using SEM microscopy to check whether the piece was printed correctly. Finally, the obtained matrix was validated by a flexural test and a finite element simulation.

In recent years, the need to minimise environmental impact has led to the exploration of sustainable materials, avoiding those derived from petroleum, considering that these materials should proceed from nature and be harmless and durable. Therefore, throughout this work, the following raw materials were used: furan resin, which comes from agricultural by-products, and basalt fibre, obtained by melting basaltic volcanic rock. Specifically, this work studies the development of a flame-retarded furan prepreg manufactured by means of a continuous process combining a double-belt lamination equipment with an impregnation system. Once the prepregs (flame- and non-flame-retarded) were obtained, they were subjected to various tests to analyse their fire behaviour, with both showing an adequate performance. However, comparing both, concerning the toxicity index (CIT_G), the flame-retarded prepreg generated fewer toxic gases during combustion than the non-flame-retarded one, although the latter showed a lower smoke density. In short, the developed flame-retarded material falls into the R1HL3 (Requirement 1 and Hazard Level 3) classification demanded by products with large areas in railway vehicle interiors, which is the maximum safety level according to the risk index established in applicable regulations. Therefore, this material could be used in any railway vehicle for indoor applications.

One of the main advantages of fiber-reinforced polymer (FRP) composites is the ability to reduce their weight while they exhibit exceptional properties such as high strength, stiffness, and resistance to corrosion, and reduction in their lifetime maintenance when they are compared to the metallic components. These features led fiber-reinforced polymer composites to have applications in the mechanical, construction, aerospace, automotive, medical, marine, and other manufacturing industries. However, the use of this type of material is not possible in all of these applications since, in certain sectors, the fire resistance property that the material must present is one of the key factors. For this reason, a thermosetting resin composed of ultraviolet (UV)-curable acrylic monomers has been used as a matrix, where transparent aluminum trihydrate (ATH) flame-retardant fillers were incorporated for manufacturing flame-retarded UV-curable composites. The composite parts were produced by using glass fiber-reinforced UV-curable prepregs. An exhaustive study of different types of ATH-based flame-retardant additives and the possible cooperation between them to improve the fire properties of the UV-curable composite was carried out. Additionally, the most suitable additive percentage to meet the railway sector requirements was also evaluated, as well as the evolution in the viscosity of the matrix and its processing capacity during the manufacture of the prepregs at 60 °C. The compatibility between the fillers and the matrix was assessed using a dielectric analysis (DEA). The fire properties of both the matrix and the final composite were established.

The technology of epoxy tooling, at present under continuous development, is used for the rapid manufacture of cost-effective tools for small batch production. It is a valid alternative with no need for expensive investment in metallic moulds for the development of new products. Current investigations are focused on improvements to the production system, improved tool performance, the cost reduction of moulds and tool manufacturing sustainability. In this paper, both the advantages and the disadvantages of epoxy tooling in injection moulding, wax injection, metal stamping and hot embossing are compared with conventional techniques. Following a brief introduction of rapid tooling technologies, the latest advances of epoxy tooling and their implementation in different manufacturing processes are all analysed. These developments refer to the production of new ad-hoc epoxy composites, increased productivity using conformal cooling channels, the reduction of the tooling manufacturing costs through waste reuse and the emerging industry 4.0 technologies for smart manufacturing and tooling. The main objective is to identify both the challenges facing epoxy tooling techniques and future research directions.

3D printing with filament extrusion technology is a process in which the thermoplastic molten material is sequentially accumulated layer by layer on a construction platform. 3D printers use a slicer software that converts 3D digital models into printing instructions. The software calculates the trajectory of the extruder within the printer, from three-dimensional mesh-based models. The input of the lamination software is a “.stl” file and the output is a “.gcode” file. For each layer, the lamination program generates the path that the printer extruder will travel, this could determine if a part is correctly made or not. The objective of this study has been to analyze, with a view to industry implementation of the 3D printing, if the slicer software used in the extrusion 3D printing of short glass fiber reinforced thermoplastic, influences the final results that are obtained in the printed parts. It has been worked with four 3D printing slicer software, and it has been analyzed if there are significantly differences in mechanical and dimensional properties in the printed parts. For which, in the printing tests, always the same filament printer, printing material, part design, ".stl" file, and values for the percentage and type of filling, height layer and skin thickness have been used. The additive material used was a 2.85 mm diameter filament of 30% short glass fiber reinforced polyamide 6. It has been concluded that the slicer software, considering the evaluated ones, influences the results of the percentage of deformation at maximum tension, of the printed parts. The influence on the values of the resistance and the tensile modulus is not significant. Keywords: Filament fused fabrication (FFF), fused deposition modeling (FDM), short fibre composites, slicer software, printing parameters, tensile strength. La impresión 3D con tecnología de extrusión de filamento, es un proceso en el que el material fundido se acumula secuencialmente capa a capa en una plataforma de construcción. Las impresoras 3D utilizan software de laminación que convierten modelos digitales 3D en instrucciones de impresión. El software calcula las trayectorias de la extrusora de la impresora, a partir de modelos tridimensionales basados en mallas. La información de entrada en el software de laminación es un archivo con extensión “.stl” y la salida es un archivo con extensión “.gcode”. Para cada capa, el programa de laminación genera la ruta que recorre el extrusor de la impresora, y determina que la impresión de la pieza sea precisa, inestable o errónea. El objetivo de este estudio ha consistido en analizar, con vistas a la implementación de la impresión 3D en la industria, si específicamente el software laminador utilizado en la impresión de termoplástico reforzado con fibra corta de vidrio, por medio de la tecnología de extrusión de filamento, influye en los resultados finales que se obtienen en las piezas impresas. Se ha trabajado con cuatro tipos de software de laminación de impresión 3D, y se han analizado los resultados en las propiedades mecánicas y dimensionales de las piezas impresas en función de software utilizado. Para lo cual, en todas las pruebas se ha fijado la impresora de filamento, el material de impresión, el diseño de pieza y el fichero “.stl”, y se han mantenido los mismos valores en las variables que definen el porcentaje y tipo de relleno interno, la altura de capa depositada y el espesor de piel. El material aditivo utilizado ha sido un filamento de 2,85 mm de poliamida reforzada con 30% de fibra corta de vidrio. Se ha concluido que el software laminador, considerando los evaluados, influye sobre el todo en los resultados del porcentaje de deformación a tensión máxima, de las piezas impresas. No siendo significativa la influencia del software en los valores de la resistencia y el módulo a tracción. Palabras clave: Impresión 3D por extrusión de filamento, compuestos de fibra corta, software de laminación, parámetros de impresión 3D, resistencia a tracción.

The need to reduce polyurethane (PU) foam waste has encouraged the development of sustainable foam formulations based on recycled raw materials and environmentally friendly additives, addressing both waste management and comparable foam properties to those based on fossil resources. In the present investigation, more sustainable water-blown rigid PU foams were investigated using recycled polyol and halogen-free flame retardants (FRs) for fire-resistant insulation applications. Two series of foam formulations were prepared: a first series with virgin polyol and the inclusion of a halogen-free FR additive (6 wt%) and a second series with recycled polyol (10% added respect to the total polyol) and halogen-free FR additives (6 wt%). Two types of FR were used: FR900, specifically identified as 3,9-Dimethyl-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane-3,9-dioxide, in powder form with 24% phosphorus content and reactive polyol based FR140, an oligomeric ethyl ethylene phosphate, in liquid form with 19% phosphorus content. The density, cellular structure, aged thermal conductivity, dimensional and hydrolytic stability, fire properties, and mechanical properties were characterized for novel foamed systems. Rigid foamed materials with very low densities around 50 kg/m³ were obtained. On the one hand, the inclusion of FR900 into the PU formulation containing virgin polyol generated foam with the lowest thermal conductivity (36.10 mW/mK) due to the smaller open cell content (11.7%) and cell size reduction (433 microns). On the other hand, the inclusion of recycled polyol reduced the foam density by 6 kg/m³ (44.1 kg/m³), increased the cell size average (848 microns) and open cell content (15.1%), maintained thermal conductivity (38.73 mW/mK), slightly improved the fire properties, and worsened the mechanical properties in comparison with the PU reference containing only virgin polyol. The results obtained by the foam containing recycled polyol and 6% FR900 are remarkable, presenting an increase in density (50.3 kg/m³) and in open cell content (73%), but a very high reduction in cell size (465 microns) and thus a low value of thermal conductivity of 37.04 mW/mK with respect to the reference material containing recycled polyol. Moreover, this PU foam containing recycled polyol and FR900 offered improved fire resistance (148.2 kW/m² of Maximum Average Rate of Heat Emission (MARHE), 179.1 kW/m² of Maximum Heat Release Rate (HRRmax), and 24.6 MJ/m² of Total Heat Release (THR)) and mechanical properties (6.97 MPa of Young’s modulus and 0.24 MPa of collapsed stress) for the construction sector. The inclusion of FR140 does not improve the properties of the foam system containing recycled polyol, mainly due to the deterioration of the cellular structure (in the open cell content and cell size).