The vanadium redox flow battery (VRFB) is considered as one of the most promising energy storage system in the future. It is composed of two endplates and a stack which consists of flow frame (FF), electrode, bipolar plate (BP) and membrane. Because the electrolytes flowing in the stack are sulfuric-acid-based solutions, prevention of leakage is important. The unified structure of the FF and the BP manufactured by co-curing E-glass/epoxy and carbon/epoxy composites not only prevents leakage, but also simplifies assembling process. However, large thermal residual stress is induced due to the difference of coefficients of thermal expansion between E-glass/epoxy and carbon/epoxy composites.
In this work, smart cure cycle was developed to reduce the thermal residual stress of the co-cured E-glass/carbon/epoxy structure for VRFB. The deformations of structure fabricated using smart cure cycle were investigated with respect to the degree of cure and post-cure process using the viscoelastic properties of composite materials during post-cure process. In addition, the thermal residual stress and actual bonding temperature were calculated. Using the experimental results of degree of cure and actual bonding temperature, a finite element analysis was performed to verify the stress of the co-cured FF BP structure as a function of the cure cycles.