Cure- and temperature-dependent rheology of a high-performance resin system for hydrogen pressure vessels

Composite pressure vessels, particularly those made of carbon fiber-reinforced polymers, are a lightweight, reliable storage solution for hydrogen. Their performance and manufacturability, however, are closely linked to the curing kinetics and rheological behavior of the thermosetting matrix during processing. This study investigates an epoxy resin system designed for hydrogen storage applications to assess its processability and suitability for filament winding. Stoichiometric and nonstoichiometric formulations containing expanded graphite nanofillers were explored to evaluate the combined effects of formulation and filler content on curing kinetics and viscosity behavior. Thermal and rheological measurements are taken over a range of temperatures under isothermal and nonisothermal conditions. An integrated modeling framework is proposed, combining cure kinetics and chemorheological models to describe the evolution of the degree of cure and viscosity during processing. The results show that formulation stoichiometry and the addition of nanofillers significantly affect reaction kinetics, gel time, and flow behavior. The suggested models accurately describe the effects of temperature, shear rate, and curing progress and remain predictive under nonisothermal conditions without requiring additional experimental inputs. Overall, the combined experimental and modeling approach is an effective tool for optimizing processing conditions and designing high-performance nanofilled epoxy matrices for composite hydrogen storage vessels.