The Hygrothermal Aging And Lifetime Prediction Of Carbon Fiber Filament-Wound NOL Rings

An accelerated aging method to characterize the hygrothermal properties of carbon fiber (CF) filament-wound composite pressure vessels in storage and using process was presented based on filament-wound composite NOL rings in this paper. The hygrothermal aging behavior of the CF /epoxy NOL rings in distilled water at 35℃, 55℃, 65℃and 75℃was analyzed in terms of the absorption characteristics, static and dynamic mechanical properties. The Arrhenius relationship was used to accelerated exposure time by increasing exposure temperature.The aim of this paper is to design the accelerated hygrothermal aging method of carbon fiber (CF) filament-wound composite pressure vessels and provide valuable data for the prediction of the storage lifetime.The moisture properties of CF/epoxy NOL rings displayed a three-stage absorption processes, with the first, second and third absorption stage being diffusion-controlled in free volume, molecular-relaxation-controlled and interface degradation-controlled, respectively. When moisture content reached 1%, the ring shear strength retention, flexural strength retention and tensile strength retention decreased to 75%, 67% and 90%, meanwhile, the Tg decreased by 20℃. Residual-cure, plastication, embrittlement, secondary crosslinking and interface degradation result in the change of properties of NOL rings. The moisture content of NOL ring reaches 1% at 25℃when NOL ring immerged in distilled water, the aging time will be 38871 hours predicted by the Arrhenius relationship. The accelerated equations at different moisture contents were also given. These results provided good basis for the prediction and estimation of the storage life of carbon fiber filament-wound composite pressure vessels.