Abstract
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.
Highlights
In the last several years, additive manufacturing technologies are polarizing the interest of industrial and scientific world due to unique characteristics and the possibility to suitably tailor the products manufactured [1]
Materials employed in 3D printing technologies are the thermoplastic polymers, due to their workability and reduced melting temperature, an indispensable feature required for the majority of printing equipments, that exploit the thermal energy obtained by means of electrical resistance [2,3]
More interest has been focused on applying Fused Filament Fabrication (FFF) technologies for printing composite material by making use of a double nozzle, in order to alternatively printing the matrix material and the reinforcement fibres to obtain lightweight and high resistance components with reduced production time and higher precision and automation compared to traditional technologies [4]
Summary
In the last several years, additive manufacturing technologies are polarizing the interest of industrial and scientific world due to unique characteristics and the possibility to suitably tailor the products manufactured [1]. The products manufactured still suffers from the major drawback that has limited the diffusion of composite materials such as low thermal and electrical conductivity and poor wear and scratch behaviour [5] For this reason, hybrid composite/metallic structures have been developed in order to improve the surface characteristics of the component, the most common metallization techniques have several disadvantages and may lead to severe surface degradation due to the high temperatures applied [6,7]. This technology allows the deposition of micrometric particles (with diameters in the order of magnitude 10-100 μm) with temperatures well below their melting point [8] This technology exploits the kinetic energy obtained by accelerating the particles by means of a carrier gas rather than using a thermal source to produce the coating. The flow of micrometric powders (1-50 μm) is accelerated by the supersonic flow of a compressed gas
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