Rheology of Thermosetting Resins During Cure for Process Modeling of Composite Materials

• Andrew Brown, Mechanical Engineering, University of Delaware

• Thomas Cender, Center for Composite Materials, University of Delaware

Thermoset polymers made from epoxy resins require detailed rheology models for use in high performance composite materials. In a typical curing process, the viscosity of a resin will change by multiple orders of magnitude as temperature increases and degree of cure advances. A successful rheology model will utilize existing constitutive equations to describe the resin under these varying conditions. To create this model, experimental data was collected to characterize the cure kinetics and viscosity of a b-staged epoxy resin. Differential scanning calorimetry (DSC) and rheological experiments were conducted in a Netzch DSC 214 and a Discovery Hybrid Rheometer respectively. The DSC was utilized to conduct constant temperature ramp experiments to measure rate of reaction and degree of cure. A cure kinetics model was then fit to this data. The rheometer was used to conduct dynamic oscillatory tests with constant temperature ramps. An Arrhenius viscosity model was fit to the dynamic viscosity data first. This model is limited because is fails to account for increasing glass transition temperature when the resin is partially cured. A second improved viscosity model utilized the William-Landel-Ferry viscosity equation to incorporate the increasing glass transition temperature and accurately model viscosity during complex curing processes.