# Development and Assessment of a 4D Printing Technique for Space Applications
## 5 Conclusions  
In conclusion, the development and assessment of 4D printed hinges have yielded compelling insights into their programming, recovery behavior, and potential applications in spacecraft structures.  
* The two iterations of the programming device played a pivotal role in influencing the 4D printing performance, with the second version showcasing superior results across all experiments.
* The correlation between programming temperature and the quality of bending outcomes underscored the delicate balance in achieving optimal shape memory effects.
* Additionally, the unexpected independence of recovery from the recovery temperature up to 150 \({}^{\circ}\)C introduced new considerations for deploying these hinges in diverse scenarios.
* The forced cool-down experiments, while revealing a nuanced interplay between cooling dynamics and 4D printing performance, indicated a potential need for methodological refinement.
* The derived use-case scenarios in spacecrafts highlighted the promising application of self-activating hinges, particularly in deploying structures such as solar arrays.
* In addition to the aforementioned insights, it is noteworthy to acknowledge the instrumental role of the A150 3D printer from Orion Additive Manufacturing in this study. A150 is an innovative tool in the realm of 4D printing, paving the way for more streamlined and efficient experimentation in the field of 4D printing.  
Conceptualization, T.R. and C.V.; methodology, T.R.; software, T.R.; validation, T.R. and C.V. data curation, T.R.; writing--original draft preparation, T.R.; writing--review and editing, T.R. and C.V.; visualization, T.R.; supervision, C.V. All of the authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The data presented in this study are openly available on GitHub at the following link: [[https://github.com/richtTim/4D-Printing-of-SMP-Hinges](https://github.com/richtTim/4D-Printing-of-SMP-Hinges)]([https://github.com/richtTim/4D-Printing-of-SMP-Hinges](https://github.com/richtTim/4D-Printing-of-SMP-Hinges)) (accessed on 14 November 2023).  
We extend our sincere gratitude to Orion Additive Manufacturing GmbH for generously providing access to their A150 3D printer, offering troubleshooting assistance, and their steadfast support during challenging moments. Their collaboration significantly enriched the depth of our study. We are equally grateful to Evonik Industries AG for supplying the crucial PEEK material, which played a pivotal role in the successful execution of our experiments.  
The authors declare no conflicts of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} CAD & Computer-aided design \\ CNC & Computerized numerical control \\ DMA & Dynamic mechanical analysis \\ DMTA & Dynamic mechanical thermal analysis \\ FDM & Fused deposition modelling \\ FFF & Fused filament fabrication \\ GEO & Geostationary orbit \\ ISS & International Space Station \\ LEO & Lower Earth orbit \\ PEEK & Polyetheretherketon \\ PLA & Polylactic acid \\ \end{tabular}