Thermosetting polymers are a popular matrix for polymer composites because of their higher stiffness, higher creep resistance and higher thermal resistance over thermoplastic polymers. Despite their technological importance, a fundamental understanding of composition-molecular structure-property relationships is still lacking. Furthermore, an understanding of the matrix-fiber interface structure and its properties is critical to understand the ultimate performance of composites.In this presentation, we will present our efforts in simulating the curing process and predicting material properties of thermoset polymers by using molecular dynamics (MD). Recently, we developed a procedure to mimic chemical reactions in the curing process of thermosets and used reactive simulations to predict their ultimate response. The results are in good agreement with available experimental data and show that atomistic simulations can capture non-trivial trends in polymer physics including the effect of temperature, thermal history and strain rate in yield and post-yield behavior. In addition, the simulations provide insight and properties that are difficult to obtain experimentally. In particular, we characterize how size affects the response of thin films including their glass transition temperature, stiffness and yield stress and develop an energy based yield criteria applicable for a wide range of loadings including different amounts of deviatoric and volumetric loads. We also used molecular dynamics simulations to characterize the in-situ curing process of the resin and the thermo-mechanical response of the graphite-reinforced epoxy composites. Both cohesive yield with strain localization and nano-void formation within the bulk polymer and interface debonding between graphite and thermoset were observed, depending on the in-plane orientation of graphite. These two mechanisms lead to different post yield behavior and can provide key insight for the development of predictive models of carbon fiber polymer composites.

Predictive simulations of amorphous composites: Their ultimate thermo-mechanical properties

246th National Meeting (2013)

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