Cryogenic Compatibility of Dissimilar-Material Photopolymer Assemblies: Interfaces, Seals, Microcracking and Leak Integrity

Cryogenic service changes both polymer constitutive response and the stresses generated at dissimilar-material interfaces. A photopolymer bonded to a metal, fibre composite, glass or elastomer can experience large differential contraction, local embrittlement and interfacial shear during cool-down. The engineering failure is often not a simple strength loss: distributed matrix microcracks can connect into a leak path, a seal can lose contact pressure, or an adhesive interface can remain apparently intact while permeability increases. Recent cryogenic-composite work shows that intrinsic molecular permeation and damage-assisted leakage must be separated experimentally. ER-384 therefore qualifies the assembly, not the bulk resin alone. Temperature history, joint geometry, thermal-expansion mismatch, crack density, leak rate and post-cycle mechanical integrity are linked in one evidence chain, with acceptance tied to the declared fluid, pressure and cycle envelope.