Additive manufacturing has profoundly influenced the aerospace industry since its inception, offering unmatched design freedom, cost reduction, rapid prototyping, and enhanced supply-chain efficiency. High-performance polymers like ULTEM™ and PEEK have emerged, known for their strength, temperature resistance, chemical resistance, and lightweight properties. However, the mechanical properties of materials produced through additive manufacturing can vary due to several factors in the printing process, leading to some degree of uncertainty. To address this, the mechanical properties of ULTEM™ 9085 and ULTEM™ 1010 were characterized through mechanical tests. These tests aimed to provide valuable insights into the performance of these materials to be able to run more practical and precise analyses in concurrent design facilities for topological optimization. The results were also compared to materials used in traditional manufacturing methods for components such as flexures and compliant mechanisms. While not fully able to replace metals in high-stress environments, they can be effectively utilized in specific applications. The tests performed contribute to the building of databases that would allow for faster access to critical data that could be applied to a simulation to predict structural performance. This research highlights the potential of additive manufacturing to revolutionize material use in the aerospace sector.

Stratospheric balloons are a valuable platform for scientific and technological experiments, as they can reach altitudes of 20 to 40 km and stay aloft for weeks or months. However, designing electronic boxes for stratospheric balloons poses several challenges, such as thermal management, mechanical stability, power consumption, and communication. The electronic box contains the main components of an experiment, such as the payload interface, the telemetry system, the data acquisition and storage, the sensors and actuators, and the power supply. This article presents some of the best practices and lessons learned from the experience of developing and testing an electronic box for the experiment HERCCULES, inside the stratospheric balloon of the BEXUS/REXUS program. The design criteria and trade-offs that were considered for each component, such as weight, size, reliability, modularity, and compatibility, are also discussed. A low-cost design with outstanding performance was obtained based on a concept that can serve as a baseline for the standardization of payload electronics of stratospheric balloons.

In the space industry, minimizing weight is essential for reducing launch costs and improving fuel efficiency. However, lighter structures have lower stiffness, making them more susceptible to vibroacoustic excitation during rocket launches, which can cause mechanical stress and potential damage. To mitigate this, absorbing materials are commonly applied in the launch vehicle fairing to convert acoustic energy into heat, reducing sound transmission and protecting sensitive payloads. However, this solution increases mass and volume, creating a trade-off. Microperforated panels (MPPs) have emerged as a promising alternative. These panels, made from metal, plastic, or wood, feature tiny perforations (0.11 mm in diameter) that dissipate sound energy through frictional losses, acting like Helmholtz resonators to enhance absorption at specific frequencies. While effective, MPPs are costly and require complex manufacturing. To address this, researchers are exploring 3D printing, which offers weight, time, and cost savings while enabling intricate designs. However, material selection remains a challenge due to mechanical property limitations and outgassing concerns in aerospace applications. In the past decade, extensive research has been conducted on materials suitable for aerospace applications, one of them being ULTEM. This material is a high-performance polymer widely utilized in aerospace due to its exceptional strength, durability, and heat resistance. This thesis aims to apply the 3D fabrication techniques, using materials certified for space applications, for the fabrication of MPPs, looking for characteristics such as speed of fabrication, precision, and low cost, for different topologies of the resulting structure. The first part of this dissertation analyzes the mechanical properties of the materials through tensile, flexural, compression, and Charpy impact tests, as polymers are anisotropic, and their properties can change easily. The mechanical tests show interesting results, with the samples obtaining a lower elastic modulus than in the datasheet, but a similar or higher strength. The samples with the best overall mechanical properties were those printed on-edge at a 45-degree angle, which matches the datasheet. The second part is the acoustic test performed on printed samples to study their absorption coefficient. When performing these tests, other issues arose involving the quality of the print. The material used can only be used with an industrial printer that limits the user's input in the printing process, which led to some of the perforations coming out obstructed and the diameters being smaller than the nominal values. The comparison of their performance with the theoretical curve was not ideal, even after adjusting the parameters and equations to take into account the porosity and other parameters. This led to the decision to print the acoustic test samples with two other materials: PEEK and ceramic resin. The PEEK samples showed the same issues as ULTEM in the quality of the print, but the ceramic resin samples used another additive manufacturing fabrication method and the perforations were of better quality and precision, only slightly oval. This also meant a better acoustic absorption performance than the other two materials, although they still differ from the theoretical curves. Overall, even with the issues, all three materials show good absorption capabilities and a broad peak without requiring a small perforation diameter. With time, with the creation of better printers, FDM could be a great alternative, but resin and CNC appear to be a better option at the moment for the production of MPPs, while FDM could also be a great alternative to metals in other types of acoustic vibration reducers, like Helmholtz resonators, for their good mechanical properties of ULTEM and capability for complex geometries RESUMEN En la industria espacial, minimizar el peso es clave para reducir costes de lanzamiento y mejorar la eficiencia del combustible. Sin embargo, las estructuras más ligeras tienen menor rigidez, lo que las hace más vulnerables a la excitación vibroacústica durante el lanzamiento, generando tensiones mecánicas y posibles daños. Para mitigarlo, se aplican materiales absorbentes en el carenado del vehículo, que convierten la energía acústica en calor, reduciendo la transmisión del sonido y protegiendo las cargas útiles. Sin embargo, esta solución aumenta la masa y el volumen, lo que supone una limitación. Los paneles microperforados (MPP) han surgido como una alternativa prometedora. Estos paneles, fabricados en metal, plástico o madera, contienen pequeñas perforaciones (0,1-1 mm) que disipan la energía sonora mediante pérdidas por fricción, actuando como resonadores de Helmholtz para mejorar la absorción en ciertas frecuencias. Aunque eficaces, los MPP son costosos y su fabricación es compleja. Para abordar este problema, se ha propuesto la impresión 3D, que reduce peso, tiempo y costes, además de permitir diseños más complejos. No obstante, la selección de materiales sigue siendo un desafío debido a sus propiedades mecánicas y los problemas de desgasificación en aplicaciones espaciales. En los últimos años, se ha investigado el uso de materiales adecuados para el sector aeroespacial, destacando ULTEM, un polímero de alto rendimiento utilizado por su resistencia, durabilidad y tolerancia al calor. Esta tesis busca aplicar la impresión 3D con materiales certificados para fabricar MPP, evaluando velocidad de producción, precisión y coste en distintas topologías. La primera fase analiza las propiedades mecánicas de los materiales mediante ensayos de tracción, flexión, compresión e impacto Charpy, ya que los polímeros son anisótropos y sus propiedades pueden variar....