multiscale simulation of nanocomposites by means of the ... · molecular dynamic finite element...
TRANSCRIPT
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
3
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
4
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
5
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“
6
1. Particle 2. Matrix 3. Composite
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
Neat Epoxy Resin: Averaged Stress-Strain Curves
7
Vir
ial
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
source: VI/DLR
Size-Dependency of Tensile Modulus
8
Introduction MDFEM Composite Modeling
Num. Results Multiscale Scheme Conclusions
Radial Density around Particle after Relaxation
9
• 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
10
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
12
Funded/Supported by
IRTG, Hannover 30.09.2013
Thank you for your attention.