Influence of cure kinetic, rheological and thermo-mechanical behavior on micro-level curing strain of an epoxy prepreg

The coupled nature of chemical kinetics, mechanical and rheological behavior of a curing prepreg dictates the dimensional accuracy of a composite laminate. In this work, an integrated study was carried out to understand the influence of thermo-chemo-mechanical and thermo-chemo-viscous effect on the curing strain of an epoxy laminate. The chemical kinetics of the resin was obtained from differential scanning calorimeter. The “instantaneous elastic modulus” was measured by using dynamic mechanical analyzer. An empirical model as a function of temperature and degree of cure (thermo-chemo-mechanical) was proposed to fit the elastic modulus data of the curing resin. This model correlates well with the experimental results offering improved accuracy than existing linear models and simpler than viscoelastic models. Rheology of the resin was investigated to obtain gelation, vitrification and viscosity information. The temperature-degree of cure-dependent viscosity was modeled empirically from the rheological data. The empirical models obtained for degree of cure, modulus and viscosity were used to predict the micro-level cure-induced strain of a curing composite and compared with experimental results.