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Nanocomposite behaviour during tensile deformation?

Influence of filler properties on the mechanical failure of a polymer nanocomposite A. Kutvonen , G. Rossi , T. Ala-Nissilä Multiscale Statistical Physics Group at COMP/Aalto. Polymer nanocomposites have a wide range of applications varying from car tyres to advanced coating technologies

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Nanocomposite behaviour during tensile deformation?

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  1. Influence of filler properties on the mechanical failure of a polymer nanocompositeA. Kutvonen , G. Rossi , T. Ala-NissiläMultiscale Statistical Physics Group at COMP/Aalto • Polymer nanocomposites have a wide range of applications varying from car tyres to advanced coating technologies • How do parameters such as loading, filler material and topology influence the nanocomposite mechanical properties? Nanocomposite behaviour during tensile deformation?

  2. MODEL & METHODS • Molecular dynamics simulations • V(r) -> F(r) -> move ->V(r) • Bead-spring model for polymers • + Lennard Jones (LJ) – potentials • Periodic boundary conditions • Fillers with different topologies, masses and sizes

  3. METHODS & STRESS – STRAIN CURVES • System equilibrated in NVT ensemble above glass transition temperature • Walls are moved with constant velocity how much system resist strain Stress Stress-Strain curve -Indicates how system resists strain Strain Elastic response Yield point Cavitation Big cavity

  4. RESULTS 1/3WHERE DOES THE STRENGTH COME FROM? 9 Stress All neighbours All neighbours Number Fraction Bead-filler neighbours Fraction • Before yield point the density of system is decreasing • Number of contacts reduces • Fraction bead-filler neighbours is increasing Bead-bead neighbours Fraction Filler-filler neighbours Strain All neighbours

  5. RESULTS 2/3 • Fixed volume loading • Size comparison • Smaller fillers increase yield stress for cavitation • No, even with constant surface area the smallest win • Smaller ones have better mobility • Is it because smaller fillers in total have a larger surface area?

  6. RESULTS 3/3 & WORK IN PROGRESS • Same number of fillers and same mass IN PROGRESS: Study of the effects of: • Mass of the filler • Loading • Stick and sheet shaped fillers • Branching vs. • Triangles might have more rigid behaviour

  7. Thank you for your attention!

  8. MD SIMULATION PROTOCOL Randomize initial positions and compress Decompress and find equilibrium volume in microcanonical ensemble Pull walls with constant velocity and gather data Equilibration by annealing

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