PSI - Issue 53

Carla M. Ferreira et al. / Procedia Structural Integrity 53 (2024) 254–263 Carla M. Ferreira / Structural Integrity Procedia 00 (2019) 000 – 000

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Nomenclature AM

Additive Manufacturing

3DP

3-D Printing

L-PBF

Laser Powder Bed Fusion Power Bed Fusion Selective Laser Melting Selective Laser Sintering Direct Metal Laser Melting Direct Metal Laser Sintering

PBF SLM SLS

DMLM DMLS

1. Introduction The aerospace sector comprises not only commercial and military aircraft, but it also incorporates space launch and in-space systems, satellites, and general aviation. Despite the recent COVID-19 world pandemic, the aerospace sector is expected to grow from 283 billion euro in 2020 to 409 billion euro in revenue by the year of 2025. This growth is primarily driven by the long-term demand for new aircraft, increased global military expenditure, and high market activity and demand in the aerospace sector. Manufacturing in the aerospace industry is a daily challenge subjected to several interacting technical and economic issues: functional performance, lead time reduction, light weighting, the complexity of geometries, cost management and sustainment. All these factors together increase the difficulty of delivering safety-critical components that must operate in their intended environment, subjected to various and complex loading conditions [1]. Notwithstanding the aforementioned issues, one of the most critical challenges on metal additive manufacturing (AM) applications in the aerospace sector is the requirement for certification, where the regulatory authorities must be confident that the AM systems are well defined and understood, and that a certain component can be repeatably designed and inspected ensuring the reliability of the process along with the achievement of the safety expectations and targets according to the criticality of the produced component [1]. AM can be used to redesign critical components such as engine parts, turbine blades, primary structures, and fuselage frames, usually using superalloys, steels and aluminium alloys. It also enables the production of less critical components like brackets, pipes, cables, aircraft interiors and secondary structural components, normally by using composites, polymers and light metals [2], while enabling mass reduction, the number of parts and reduction of assemblies, resulting in lead time reduction and increasing the performance of the components. Metallic AM systems can be classified as Powder-Bed Fusion (PBF), Direct Energy Deposition (DED) and Droplet-on-demand. The PBF technologies can be further divided into two well-known and widely studied processes, the Selective Laser Melting (SLM), also known as Laser Powder Bed Fusion (L-PBF), and the Electron Beam Melting (EBM), being the former the predominant industrially developed process concerning the AM of metals [3]. L-PBF process uses powder feedstock, with most of the commercially available alloys in the form of powder such as aluminium alloys, nickel alloys, titanium alloys, cobalt alloys, copper alloys, magnesium alloys, steels alloys and pure metals. Aluminium alloys, especially the cast alloys, are great candidates to be processed by L-PBF for performance and lightweighting applications since they offer a good compromise between strength and density and are relatively inexpensive. One of the advantages of L-PBF processing Al cast alloys is the microstructure enhancement resulting in improved mechanical properties, with AlSi10Mg receiving most attention by the process [3]. Over the last two decades the state-of-the art regarding AM has been growing and since the research on AM has matured considerably, allowing for a deeper understanding of its applications and benefits in the aeronautical sector, the authors considered that there is still fragmented and disperse information of the applications regarding this sector, which leads to the misidentification of solutions to overcome the major drawbacks associated with L-PBF processes and areas for potential innovation and development. The aim of this paper is to shed light upon the current state-of the-art available in the aeronautical and aerospace sectors by highlighting their current trends and applications