Composites Containing Barrier Layers for Reduced Permeability at Cryogenic Temperatures

摘要

To help prevent leakage that may occur if cracks develop in a cryogenic composite pressure vessel due to thermo-mechanical fatigue, liners are occasionally implemented. However, liners can be difficult to fabricate and maintain, and mismatch of their CTE with the underlying composite can promote debonding of the liner. In this effort, two approaches to incorporating a barrier layer directly into a carbon/bismaleimide PMC (IM7/5250-4) were investigated for their effectiveness in preventing the development of through- thickness crack networks that can lead to leakage. In the first concept, a 'thin ply' of T800 carbon fiber/5250-4 bismaleimide composite much thinner than a standard 0.13 mm thick ply was placed adjacent to the surface plies or mid- plane ply group where cracks initiated first. This arrangement was chosen to help prevent crack growth beyond these early-cracking plies. Overall the thin plies were successful both in limiting 'stitch crack' propagation into the neighboring plies and in limiting the overall interior ply damage. In the second concept, an even thinner layer.