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Molecular Dynamics Analysis of Silica/PMMA Interface Shear Behavior.
Koochul Ji1, Lauren K Stewart1, Chloe Arson1
1School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0355, USA.
Polymers
|March 10, 2022
Summary
Molecular Dynamics simulations reveal that longer polymer chains and rougher interfaces enhance the shear strength of epoxy-injected cementitious materials. Optimal performance is achieved with long, entangled chains, not just surface filling.
Area of Science:
- Materials Science
- Computational Mechanics
- Polymer Science
Background:
- Quantitative modeling of epoxy-injected cementitious materials is limited.
- The atomic-level mechanisms of polymer/concrete interface shear strength are not well understood.
Purpose of the Study:
- To investigate parameters influencing crack filling and interface strength in mode II for polymethylmethacrylate (PMMA)/silica systems.
- To elucidate the role of injection conditions and polymer chain length on mechanical properties.
Main Methods:
- Molecular Dynamics (MD) simulations were employed to model PMMA injection and shear deformation at the PMMA/silica interface.
- Simulations varied injection pressure, temperature, strain rate, and polymer chain length.
Main Results:
- Notch filling ratio increases with pressure and temperature, decreases with chain length.
- Interface shear strength rises with strain rate; rougher interfaces are stronger than smooth ones.
- Longer polymer chains and higher filling ratios on rough interfaces increase shear strength, with a critical drop at PMMA's melting point (400 K).
Conclusions:
- Entanglement of long polymer chains yields higher interface shear strength than asperity filling by short chains for equivalent injection work.
- Van der Waals forces dominate, but interlocking forces are crucial for long chains, reducing failure energy.
- Long polymer chains and low filling ratios on rough interfaces are more efficient for enhancing mechanical properties.
