https://popups.uliege.be/esaform21/index.php?id=2439 Publications of Auteurs Antonello Astarita fr 0 https://popups.uliege.be/esaform21/index.php?id=4131 Niobium is a ductile transition metal of growing interest for several technological applications, thanks to its intriguing characteristics, among them high melting point, moderate density, good ductility, high corrosion resistance and superconductivity. By contrast, its use is limited by some weaknesses lied to the mechanical properties, which can undermine the quality of the surfaces worked by metal forming processes. Sheets of pure Niobium can be used for the manufacture of extremely customized components and a flexible process like the incremental sheet forming fits well with this manufacturing philosophy; in fact, this technique does not require complicated tools and/or dedicated equipment and is capable to respond quickly to the market demands. The scope of this paper is to investigate the influence of the tool/sheet contact conditions on different features like the forming loads, the surface quality and the occurrence of failures, when pure Niobium rolled sheets are formed incrementally. To this aim, the simplest variant of incremental sheet forming, namely single point incremental forming, was considered by using a common fixed end forming tool with hemispherical head. The process was carried out under dry and lubricated tool/sheet contact conditions, following the indications from a preliminary campaign of wear tests conducted by a pin-on-disk apparatus. The experimental campaign highlights the strong influence of the tool/sheet contact conditions and the importance of a correct choice of them on the features investigated, in order to limit the forming forces and the risk of failure, as well as to preserve the surface quality of the components made by incremental sheet forming of Niobium. Wed, 31 Mar 2021 09:09:19 +0200 Wed, 31 Mar 2021 09:09:19 +0200 https://popups.uliege.be/esaform21/index.php?id=4131 https://popups.uliege.be/esaform21/index.php?id=4017 Polymer-based AM methods are the most mature additive technologies for their versatility and variety of products obtainable. The addition of fibre reinforcement can also confer to the manufactures produced good mechanical properties. Unfortunately, several applications are still precluded because polymers cannot guarantee appropriate electrical conductivity, erosion resistance and operating temperature. Aiming to overcome these issues, the metallization of the surfaces emerges as a possible solution. Unfortunately, thermoplastic polymers exhibit thermosensitive behaviour and run the risk of being damaged when traditional metallization techniques, which require the melting of metal powders which will act as a protective coating. For this reason, studies have focused on Cold Gas Dynamic Spray, an additive manufacturing technology, which exploits kinetic energy to favour the adhesion of metal particles rather than the increase in temperature. In this work, a first attempt is made to verify the feasibility of cold spray coatings on 3D printed composite substrates, produced by means of Fused Filament Fabrication (FFF) technique. FFF technology allows the deposition of two different types of filaments by using a double extruder. These composite fibres within 3D printed parts manage to give the object a resistance comparable to that of a metal part with lower production cost and a high degree of automation. These structures, made of ONYX, a Nylon matrix in which short carbon fibres are dispersed, and reinforced with long carbon fibres, are designed to better fit the CS deposition. Aluminium coatings have been produced and a characterization campaign has been carried on. Tue, 30 Mar 2021 10:01:16 +0200 Tue, 30 Mar 2021 10:26:30 +0200 https://popups.uliege.be/esaform21/index.php?id=4017 https://popups.uliege.be/esaform21/index.php?id=3003 PMCs are anisotropic and heterogeneous structures with excellent performances in terms of mechanical strength and stiffness, coupled with reduced weight, widely used in engineering sectors. The use of PMCs can be further extended by improving their surface properties such as electrical conductivity, erosion, radiation and lightning protection. In this context, the surface metallization seems to be best solution. In particular, the cold spray (CS) technique candidates as a potential method for the manufacturing of a metal coating on PMCs’ surface. However, the design and the manufacturing methods of PMCs can play a crucial role for an effective metallization through CS. The additive manufacturing technologies for composite materials can be used to manufacture customized reinforced polymer-based panels, like PMCs; the most common method for printing them is the Fused Filament Fabrication (FFF) technique which relies on the thermal extrusion of a thermoplastic feedstock from a mobile heated nozzle. Therefore, this research activity aims to manufacture customized PMCs panels by using FFF technology for the substrate and the cold spray technique for the metallization in order to study the influence of the substrate manufacturing strategy on CS deposition process. For this purpose, three kind of 3D-printed PMCs were manufactured through the FFF technology by varying the percentage fill of the Onyx polymeric matrix and aluminum powders were sprayed on the substrates with a low-pressure cold spray (LPCS) system; both FFF and CS process parameters were varied to study the process in its wholeness. Microscope analyses were carried out to analyze the influence of the manufacturing strategy on the coating quality. Fri, 26 Mar 2021 15:15:18 +0100 Fri, 02 Apr 2021 17:01:44 +0200 https://popups.uliege.be/esaform21/index.php?id=3003 https://popups.uliege.be/esaform21/index.php?id=2727 Metallization is a common strategy employed to enhance the electrical and thermal conductivity of polymer matrix composite materials. Nevertheless, metallic deposition on polymer-based materials is challenging due to the inherent limitations related to high temperature exposure of the substrate. In this article, a new technique for the manufacturing of composite laminates and the subsequent metallization by cold spraying of metallic powder is presented. The composite manufacturing route is based on the production of thermoplastic-thermoset hybrid substrates and consisted of two main stages: in the first stage the partial impregnation of a reinforcement textile by a thermoplastic film was promoted by hot pressing compaction. Afterwards, the prepared lamina was vacuum bagged with other reinforcing layers and impregnated by the thermoset catalyzed resin by a vacuum infusion process. Finally, the thermoset and thermoplastic layers were co-cured to increase the adhesion of the substrate with the thermoplastic film. The metallization of composite laminate was obtained through the cold spraying technique, depositing powders on the thermoplastic surface layer. The effect of processing parameters on the coating deposition, quality and microstructure was reported and discussed. Wed, 24 Mar 2021 18:51:23 +0100 Fri, 09 Apr 2021 10:28:26 +0200 https://popups.uliege.be/esaform21/index.php?id=2727 https://popups.uliege.be/esaform21/index.php?id=2433 Powder bed additive manufacturing allows for the production of fully customizable parts and is of great interest for industrial applications. However, the repeatability of the parts and the uniformity of the mechanical properties are still an issue. More specifically, the physical mechanism of the spreading process of the powders, which significantly affects the characteristics of the final part, is not completely understood. In powder bed fusion technologies, the spreading is performed by a device, typically a roller or a blade, that collects the powders from the feedstock and successively deposits them in a layer of several dozens of microns that is then processed with a laser beam. In this work, an experimental approach is developed and employed to study the powder spreading process and analyze in detail the motion of the powders from the accumulation zone to the deposition stage. The presented experiments are carried out on a home-made device that reproduces the spreading process and enables the measurement of the characteristics of the powder bed. Furthermore, the correlation with the process parameters, e.g., the speed of the spreading device, is also investigated. These results can be used to obtain useful insights on the optimal window for the process parameters. Tue, 23 Mar 2021 19:02:41 +0100 Mon, 29 Mar 2021 20:19:10 +0200 https://popups.uliege.be/esaform21/index.php?id=2433 https://popups.uliege.be/esaform21/index.php?id=858 Composite materials are widely used as main parts and structural components in different fields, especially for automotive and military applications. Although these materials supply different advantages comparing to the metals, their implementation in engineering applications is limited due to low electrical and thermal properties and low resistance to erosion. To enhance these above-mentioned properties, the metallization of composite materials by creating a thin metal film on their surface can be achieved. Among different coating deposition techniques, Cold Spray appears to be the most suitable one for the metallization of temperature-sensitive materials such as polymers and composites with a thermoplastic matrix. This process relies on kinetic energy for the formation of the coating rather than on thermal energy and consequent erosion and degradation of the polymer-based composite can be avoided. In the last years, a new method to produce composite materials, as known as Fused Filament Fabrication (FFF), has been developed for industrial applications. This technique consists of a 3D printing process that involves the thermal extrusion of thermoplastic polymer and fibers in the form of filaments from a heated mobile nozzle. The implementation of this new technique is leading to the manufacturing of customized composite materials for the cold spray application. In the presented experimental campaign, Onyx material is used as a substrate. This material is made of Nylon, a thermoplastic matrix, and chopped carbon fibers randomly dispersed in it. Aluminum powders were cold sprayed on the Onyx substrate with a low-pressure cold spray (LPCS) system. This study aims to investigate the possibility of the metalizing 3D-printed composite material by cold spray technology. For this purpose, optical and microscopical analyses are carried out. Based on the results, the feasibility of the process and the influence of the morphology of the substrate are discussed, and optimal spraying conditions are proposed. Sun, 21 Mar 2021 22:20:35 +0100 Tue, 30 Mar 2021 11:03:16 +0200 https://popups.uliege.be/esaform21/index.php?id=858