Gas permeability of various graphite/epoxy composite laminates for cryogenic storage systems

Experiments were performed to investigate the effect of cryogenic cycling on the gas permeability of various composite laminates for cryogenic storage systems. Textile composites have lower permeability than laminated composites even with increasing number of cryogenic cycles. Nano-particles dispersed in one of the ply-interfaces in tape laminates do not show improvement in permeability. Micrographs of sections of various specimens provide some insight into formation of microcracks, and damage before and after cryogenic cycling. In laminated tape composites microcracks in various layers connect and form an easy path for gas leakage. Composites wherein plies of different orientations are dispersed rather than grouped show excellent performance even after cryogenic cycling. In textile composites the damage is restricted to regions contained by the weave yarns and hence the permeability does not increase significantly with cryo-cycling.