A thermo-mechanically coupled constitutive model for curing of polymers

Thermoplastics and Thermosetting polymers have found wide variety of applications these days in automotive, electronics, healthcare and aerospace industries due to their lightweight, easy formability etc. One of the major challenge in the manufacturing and processing of thermosets and thermoplastics is curing, through which the liquid polymer transitions into a state of visco-elastic and/or viscoplastic solid. The curing process is a coupled thermo-chemo-mechanical conversion process which requires a thorough understanding of the constitutive behavior to predict cure dependent mechanical behavior of the solid polymer. In this work, a thermodynamically consistent, frame indifferent, coupled chemo-mechanical continuum level constitutive framework is proposed for thermally cured glassy polymers. The constitutive framework considers the thermodynamics of chemical reactions, as well as the material behavior for a glassy polymer. This work considers a definition for the degree of cure based on the chemistry of the curing reactions. A simplified version of the proposed model has been numerically implemented, and simulations are used to understand the capabilities of the model and framework in typical composites specimen.