Session: 01-02 Polymers: Characterization and Mechanical Properties II

Paper Number: 91989

91989 - Effects of Printing Parameters on Geometrical and Mechanical Properties of 3d-Printed High-Performance Thermoplastics, Toward the Digitalization of Power Transformers. 

Cellulose has been the raw material of choice used to form solid insulation materials widely used in power transformers, such as, paper and pressboard, due to its availability, conjugated with the good electrical insulation, oil absorption and mechanical properties of the final parts. However, the cellulosic material has several disadvantages, namely its hygroscopic characteristics which raises the need of several time-consuming processes, for example, to avoid the insertion of moisture inside the transformer tank.

In addition, many transformer parts are mainly manufactured either (i) by very elaborate and extremely time-consuming processing of paper and pressboard, which are not in line with the new paradigms of work automation and digitization, or (ii) by subtracting processes (milling, turning, etc.) from plates of laminated densified wood, of different dimensions and thicknesses. This combination of raw material and manufacturing process leads to low efficiency of raw material use, and limits the functional optimization of parts, and so, the development of new constructive concepts and functionalities.

The fact that cellulose is not the best material for these applications fosters the research of new materials, and simultaneously brings into discussion the production processes. At this point the additive manufacture can be positioned as a viable alternative, and as the potential to become a core technology in the conceptual development of power transformers.

A diversified range of AM technologies have been created since the AM creation in the 80s. Nowadays, Fused Filament Fabrication of thermoplastics is one of the most popular Additive Manufacturing process due to the availability of affordable open-source equipment. In general, open-source 3D-printers are suitable for processing common thermoplastics, e.g. Acrylonitrile Butadiene Styrene (ABS), Polylactic Acid (PLA), Polycarbonate (PC) and Polyamide (PA). However, high-performance thermoplastics, such as Polysulfone (PSU), Polyphenylsulfone (PPSU), Polyetherketoneketone (PEKK), Polyetheretherketone (PEEK) and Polyetherimide (PEI), require high extrusion temperatures with both heated print bed and well-insulated thermal chambers, which are normally found only in expensive industrial solutions. In other words, conduct parametric studies involving the experimental characterization of those materials eventually have a high cost associated. As a consequence, there is a lack of studies in the literature about the influence of printing parameters on their resulting properties. Thus, in order to fill this gap, the present work aims to present a numerical prediction of geometrical and mechanical properties of 3D-printed high-performance thermoplastics considering the influence of printing parameters. For this purpose, a parametric study is performed and the residual stresses, as well as the distortions, are computed considering different ranges of extrusion temperatures, printing speeds, and layer thicknesses, for each material. Then, the mechanical properties are predicted using the Asymptotic Homogenization technique. To this end, unit cells with different resulting microstructures, including different void shapes and contents, are adopted. The obtained results are very promising and can be employed to drive future experimental investigations that might be conducted. For instance, they can support the definition on the design of experiments, which consequently reduces associated costs, saving time and efforts. Lastly, it can be mentioned that the present contribution opens the door for future applications of 3D-printed high-performance thermoplastics in different sectors, such as the energy sector, providing thoughtful insights for both the scientific community and industry.

Presenting Author: Cristiano Pereira Coutinho Efacec

Presenting Author Biography: PhD and MSc in Mechanical Engineering at Faculty of Engineering of the University of Porto (FEUP). In the Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), from 2012 to 2017, he was responsible for scientific research and product development driven by numerical simulation of thermo-mechanical, static and dynamic structural responses. He was also responsible for implementation and exploration of topology optimization tools, aiming 3D printing of optimized innovative structures. He joined the R&amp;D team of Transformers Unit at Efacec, in 2018, and until 2021, he was responsible for the development and experimental validation of vibro-acoustic models of Power Transformers, aiming the development of low-noise transformers. Since then, he has been the Project Manager of the &#180;Transformer4.0&#180; R&amp;D project, devoted to the digital revolution of Power Transformers, and, within the project, the technical coordinator of the research related with the Additive Manufacturing applied to Power Transformers.<br/>As a result of all the referred R&amp;D activities, he is the 1st author of one patent, author of several scientific publications, presenter in international conferences, and invited professor in the Polytechnic of Porto - School of Engineering (ISEP).

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