Gas permeability of three-dimensional stitched carbon/epoxy composites for cryogenic applications

3D through-the-thickness stitching can be used to improve interlaminar properties of polymer matrix composites (PMCs) and produce lightweight, unitized structures for cryogenic storage tanks. To fully utilize stitched composite these applications, their inherent gas permeability challenges must understood. Therefore, the effects cycling on permeation three-dimensional PMCs are investigated. Stitched unstitched carbon/epoxy standard modulus (237 GPa) intermediate (290 carbon fibers were thermally cycled helium was measured at selected cycles. Results show that increases in PMCs, with having approximately twice specimens. Optical microscopy images cracks develop resin rich areas around seams. These internal increase midspan microcrack density leads composites.