Creep

1050 Words5 Pages
Polymeric materials are widely used in industrial applications which require high level of stress. Thus understanding the mechanisms of the mechanical properties of these materials can impact the quality of the industrial products.
Epoxies demonstrate time and temperature dependent of mechanical properties specifically the creep compliance. As the constant load is being applied on the system, the material starts slow deformation. At primary stage, the creep rate decreases with time and reached to steady state value (secondary stage) which is followed by sudden increase which is known tertiary stage. It is known that creep compliance increases with temperature at constant stress load1. In an experimental study by Plaseied and Fatemi2, they presented the creep test results at different temperature and stress load for vinyl ester polymer and its nanocomposite which contained nanofibers. Also, an analytical power law function was fitted to creep test results in order to explain the behavior of the creep experiments. Both systems i.e. the neat system and nanocomposite showed similar creep behavior at low stress load. But at higher stress load, their results showed that the neat system has higher creep compliance compared to the nanocomposite T = 50 °C. On the other hands, at higher temperature (close to Tg) T = 75 and 100 °C the nanocomposite showed higher creep compared to the neat system. Tehrani et al.3 studied the mechanical properties of the multiwall carbon nanotubes/epoxy nanocomposite system, where the Aeropxy was selected as the material. Creep tests were performed at different temperatures and stress load. Their results exhibited that the creep compliance of the neat epoxy is more dependent on duration of the ...

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...ature of the material, curing condition and temperature of the experiment1. The results of the simulations suggest that the curves can be superposed and the creep compliance for any thermal history could be predicted.

FIGURE2. Creep compliance of the neat epoxy system as function of the simulation time.

Conclusion
We have used MD simulation for the first time to study the creep compliance of epoxy structures. Our results suggest that at temperatures above Tg, epoxy shows much creep behavior compared to glassy state at constant stress load. Overall view of current simulations study shows good agreement with available experimental data in literature for highly cross-linked system and there is a possibility of comparing the simulation results by applying the time temperature superposition principle to predict the long term creep compliance of a material.
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