Additive manufacturing of polymers and composites for applications in aerospace and aeronautics

This comprehensive review emphasizes the significant role of additive manufacturing (AM) in transforming the production methods of aerospace and aeronautical real components. Reducing part assembly and manual interventions and related expenses, together with the possibility of just-in-time production of customised geometry and material-saving structures, are the main reasons for aeronautical interest in 3D printing technology. From a broader perspective, 3D printing allows not only the production of parts on Earth that are intended for deployment in space missions later (FOR-space 3D printing), but also onboard production and maintenance (IN-space 3D printing). New approaches, such as artificial intelligence and machine learning, have emerged as powerful tools for optimized designs, quality control, and process parameter definition, able to consider performance criteria, material properties, and manufacturing constraints. In this context, the present review explicitly examines the working principles, material requirements, and process parameters of prominent 3D printing methods in aerospace and aeronautics, including fused filament fabrication (FFF), direct ink writing (DIW), stereolithography (SLA), materials jetting (MJ), and selective laser sintering (SLS). Particular attention is given to polymeric composites and nanocomposites and their smart functions (e.g., piezoresistivity, piezoelectricity, self-healing, and electro-thermal heating). In addition to these points, one of the main goals of the present review is to analyse the real-world examples from industry leaders such as NASA and Boeing, illustrating practical implementations. Reviewing the industrial advancements makes the reader aware of how much AM technology has been developed on an industrial scale in highly exigent sectors, paving the way to understanding the future trends of research activities. Within this scope, at the end of the review, a comparison of the different technologies, and their advantages and disadvantages is presented together with the future challenges to be addressed.