Title: High Strain Composites for Space Applications: Challenges of Fabricating Long Deployable-Stowable Booms

Authors: Craig S. Hazelton, Brian Sanders, Anan Takroori, Zach McConnel

DOI: 10.33599/nasampe/c.24.0336

Abstract: High-strain composites (HSC) enable stowable structural members for large space applications, such as solar sails, or laser accelerated light sails, however the long lengths (30 m, [100 ft]) required present tremendous fabrication challenges. The main issue is inconsistency in geometry in the form of bowing, arching, and twist of linear booms. This application requires specially designed thin layups that achieve very large strain limits to allow packaging the booms in small volumes to fit into standard launch vehicles. Due to cost constraints, stainless steel molds (large part to mold CTE mismatch) are used instead of low CTE metal or composite and an out-of-autoclave process is developed with custom equipment built in-house to control of mold and oven movement as well as airflow and thermal gradients. In general, the technique proves to reduce inconsistencies in part geometry. In particular, the process was found to work very well with 7m booms, but geometric issues flare during scale up to the 30m length. Both the thin laminate and the long length amplify issues that create the problematic geometry. Preform distortion, thermal expansion mismatch, mold and oven movement, bagging stack up, fiber wetting and all lead to issues with dimensional and geometric consistency. To achieve the desired part consistency in 30 m booms, special techniques are used to apply the preform to the mold to eliminate distortion that can create uneven residual stresses. The catalyzed epoxy novolac matrix limited options for changing the cure profile, however long dwells at sub-curing temperature reduce problems. Furthermore, a special bagging stack technique was developed to balance resin distribution through the thin laminate. Finally, adequate fiber wetting is addressed by finding a compatible carbon fiber and finish (there is a limited selection due to very thin fabric required for HSC’s) through trial and error.

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Conference: CAMX 2024 | San Diego CA

Publication Date: 2024/9/9

SKU: TP24-0000000336

Pages: 10

Price: $20.00