Molecular Dynamics Simulation of Hydrogen Permeation Behavior in Epoxy Resin Systems

Area of Science:

• Materials Science
• Chemical Engineering
• Aerospace Engineering

Background:

• Liquid hydrogen (LH2) storage in composite pressure vessels is critical for aerospace.
• Hydrogen permeation through epoxy resin matrices poses risks to cryogenic vessel integrity and safety.
• The micro-scale behavior of hydrogen permeation in epoxy resins is not well understood.

Purpose of the Study:

• To investigate hydrogen molecule permeation in epoxy resin systems using molecular dynamics (MD) simulations.
• To analyze the influence of cross-linking degree and temperature on hydrogen permeation.
• To explore the impact of material defects on hydrogen permeability.

Main Methods:

• Molecular dynamics (MD) simulations were employed to study hydrogen permeation in two epoxy resin systems (DGEBA with DDM and PEA curing agents).
• Simulations analyzed the effects of varying cross-linking densities and temperatures.
• Uniaxial tensile simulations were used to introduce defects and model their influence on permeation.

Main Results:

• Increased cross-linking density was found to inhibit hydrogen permeation by creating more tortuous diffusion pathways.
• Hydrogen adsorption and permeation exhibited high sensitivity to temperature, with increased permeation at lower temperatures.
• Simulated micro-defects showed good agreement with experimental helium permeability, validating the model's realism.

Conclusions:

• Findings provide crucial theoretical insights into the micro-scale mechanisms of hydrogen permeation in epoxy resins.
• Optimizing cross-linking and understanding temperature effects can mitigate hydrogen permeation.
• The study facilitates the development of advanced epoxy resins for safer and more efficient liquid hydrogen storage in aerospace applications.