Morgane Domerg, MAPIEM Laboratory, University of Toulon
Benjamin Ostré, MAPIEM Laboratory, University of Toulon
Yoann Joliff, MAPIEM Laboratory, University of Toulon
Yves-Henri Grunevald, CES WORKS
Morgane Domerg, Ph.D Student, MAPIEM Laboratory, University of Toulon
To orient payloads such as cameras, antennas or sensors on small satellites, a 2-axis polymer-based joint of ±45° rotation range per axis is in development [1]. This mechanism can extend opportunities for satellite buses to individually adapt the orientation of their payloads while expanding their visual range. To ensure precise motions and durability, the joint is composed of a monolithic, compliant mechanism instead of a traditional assembly of parts. Indeed, compliant mechanisms only use the elastic deformation of their structure to create complex movements. Therefore, they are not subject to wear or backlash, and they do not need lubrication. These qualities make them adequate candidates for space applications [2]. Compliant mechanisms like the one presented in this study can have intricate structures, which is why 3D printing is the process chosen to produce this joint. However, there are still many questions about the ability of 3D printing to create parts that can both ensure sufficient mechanical properties and withstand space environmental conditions.
Through this study, two polymers printed via Fused Filament Fabrication (FFF) are compared: PolyEtherKetoneKetone (PEKK) and PolyEtherEtherKetone (PEEK). These high-temperature materials are often used in the aerospace field as matrixes for composites. This work aims to characterize 3D printed PEKK and PEEK and use the mechanical properties of the best-performing material to create a finite element analysis of the joint. Then, the model is validated with experimental measurements.
Two filaments are used in this work: PEKK-A from KIMYA© and Z-PEEK from ZOTRAX©. This last filament has been chosen because it meets ESA’s outgassing requirements according to the ECSS-Q-ST-70-02C test standard. The characterization of these two materials is conducted through several tests. Thermal properties were determined using Differential Scanning Calorimetry (DSC), whereas the tensile and flexural behaviors of the materials were studied according to the ISO 527 and ISO 178 test standards. The samples were printed with a VOLUMIC© Ultra CS2 printer. Based on previous works [3] and literature [4], printing parameters such as printing speed, bed temperature, layer thickness or printing direction greatly impact both mechanical and thermal properties. Moreover, post-printing heat treatment can improve the crystallization of 3D printed polymers. This is why the studied materials are printed with the same parameters but the printing temperature, since their melting temperature differs: 308°C for PEKK-A and 365°C for Z-PEEK. As they are both semi-crystalline polymers, they also undergo heat treatment after printing to increase the crystallization rate of the materials.
The properties of the best-performing material determined during the characterization tests are used to create a static finite element analysis on the software ABAQUS©. The model is simplified by focusing on a section of the 2-axis joint: the cross-axis flexural pivot. This compliant part is composed of two crossing blades at their midpoints. The mechanical behavior of 3D printed cross-axis flexural pivots is compared to their numerical twin thanks to image correlation software. The displacements caused by the application of a force on the pivot are compared, then discussed.
For future works, vibration tests will be performed and compared to a finite element analysis based on the previously developed static model.
[1] Domerg et al, The Development of a 3D-Printed Compliant System for the Orientation of Payloads on Small Satellites: Material Characterization and Finite Element Analysis of 3D-Printed Polyetherketoneketone (PEKK), 2024