Andreas Kempe, Lutz Nasdala, Raimund Rolfes
Institute of Structural Analysis, LUH
Multiscale Simulation of Nanocomposites by means of the Molecular Dynamic Finite Element Method
IRTG, Hannover 30.09.2013
Introduction to Nanocomposites
• Nanoparticles exhibit a large specific surface
• Can be used to modify material properties
• Size effect/dependency
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2,6 g Al2O3 = 260 m2 (tennis court)
• Virtual Institute: Enhancement of properties of CFRP by means of Nanoparticles
• Central Questions: Mechanims of Particles? Role Particle-Matrix Interface?
Improve compressive strength by 21% with 15 wt.% boehmite nanoparticles
source: VI/DLR
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
Molecular Dynamic Finite Element Method
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MDFEM1),2)
Superposition
Molecular Dynamics
DREIDING Force Field
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
1) Nasdala, Kempe, Rolfes, Computers, Materials & Continua 2010. 2) Nasdala, Kempe, Rolfes, Composites Science and Technology 2012.
Nanocomposite Modeling
• System: γ-Al2O3 nanoparticles in epoxy matrix
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SEM image of UD layer modified using focused ion beam (FIB)
Nano- particle
Fiber Fiber
… …
…
…
• homogeneous particle distribution
• unit cell approach
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
SEM image of UD layer
Nanocomposite Modeling
• Structure Generator: Randomized unit cell
• Matrix: LY556 epoxy resin; HY917 Anhydride Curing Agent
• Particle-Matrix interaction: physical bonds
MDFEM Simulation Procedure
1. Relaxation: Minimize Energy, [Equilibration: Thermostat] 2. Loading: Apply 5% tensile strain, „quasi-static analysis“
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1. Particle 2. Matrix 3. Composite
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
Neat Epoxy Resin: Averaged Stress-Strain Curves
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Vir
ial
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
source: VI/DLR
Size-Dependency of Tensile Modulus
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Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
Radial Density around Particle after Relaxation
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• Density increases around particle
Distance to Particle Core [Å]
Particle Matrix
Radial Density
cell density: 1.2 g/cm³
Den
sity
[g/
cm^3
]
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
Multiscale Simulation of Nanocomposites
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Homogenization of Particle Core
Homogenization of Matrix Material
Handshaking Region:
Bridging Domain Method1)
Energy scaling factor
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
1) Xiao, Belytschko, Comp. Meth. in Apl. Mech & Eng 2004.
Numerical Homogenziation
Conclusions & Outlook
• MDFEM simulation of nanocomposites: Predict properties and gain insights into mechanims due to MD
• Interface central role in nanocomposites: e.g. size-dependent tensile modulus due to increased density at interface -> special Multiscale Scheme
• Virtual Material Development at the Nanoscale
• Current Work: Nanocomposite VE/RVE
11 Introduction MDFEM Composite Modeling
Num. Results Multiscale Conclusions
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Funded/Supported by
IRTG, Hannover 30.09.2013
Thank you for your attention.