Structural

Concerning the UPSat structural subsystem, our goal and one of our mission objectives was to implement Composite Materials to the structural frame of our CubeSat. The initial idea of a full composite structure was abandoned due to accessibility and compatibility with the internal of the P-POD issues. So, the design presented here is a “hybrid” structure consisting of both Composite Materials and Aluminum Alloy and will be designed and built entirely in-house at the premises of University of Patras. 

The design concept that followed is based at the commercial available CubeSat structures; an aluminum frame consisting of four rails and four square parts surrounded by four sides. The basic reason for following this road is the mass saving and secondly the very good mechanical properties the Composite Materials offer. Finding the best lamination for the Composite sides the structure can withstand the applied loads at all three axes as verified via Finite Element Analysis.  

 

Structure Breakdown

  • CFRP faces: Lamination: [0/45/90/-45]S
  • Aluminum (7075-T6 Alloy)
  • RAILS: Hard Anodized
  • Bolted Connections: M3 Stainless Steel-Hex Socket Button Head

 

Structural subsystem
Structural subsystem

Electronics Stacking

All PCBs were considered stacked along the Z-direction using both COTS and customized Βrass spacers

 

 

Dimensions and Center of Mass

All requirements from CDS and QB50 mission concerning the external dimensions and the COM position of the fully assembled system were fulfilled

 

COG and External Dimensions
COG and External Dimensions

Finite Element Analysis

Detailed FE Model was created and all loading scenarios (QB50 requirement) were considered:

  • Resonance Frequency (>90 Hz)
  • Quasi-Static Analysis (13g Inertial Load)
  • PSD and Sine Vinration Analysis
  • Thermal/Orbital Analysis (ISS trajectory)

Manufacturing

The manufacturing of the CFRP components took place at the AML/UPAT premises and the standard prepreg-autoclave procedure was followed according to the curing cycle provided by the material data sheet. The material used is a Cyanate-Ester/Carbon unidirectional pre-preg [HTM143/M55J (6K)] provided by CYTEC.

Concerning the laminations of the CFRP faces one lay-up was used based on the FEA campaign results.

  • [0/45/90/-45]S – 8 layers, 1mm thickness for the ±X and ±Y sides

All the Aluminum parts were manufactured at the University’s machine shop using the 7075 Aluminum Alloy.

 

Structural designs of UPSat
https://github.com/librespacefoundation/upsat-structural
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