This study uses molecular dynamics simulations to model the deformation behavior of tungsten fiber reinforced copper matrix nanowires. Tungsten fibers are packed into ceramic tubes and infiltrated with copper through liquid phase infiltration. The simulation models tungsten and copper atoms and applies strains of up to 150% to analyze the stress-strain behavior. Reinforcing copper with tungsten fibers increases the yield strength to around 4.5 GPa and delays necking. Visual Molecular Dynamics snapshots show the tungsten fibers restricting deformation of the copper matrix. The results are verified by comparison to experimental data.

1. A simulation study on deformation
behavior of tungsten fiber reinforced
copper matrix nanowire
Subodh Rana1 & Natraj Yedla2
1. Dept. of Metallurgical and Materials Engineering, NIT Jamshedpur
2. Dept. of Metallurgical and Materials Engineering, NIT Rourkela

2. Introduction
Tungsten wire
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Copper sheet
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A
B
Tungsten fiber reinforced copper matrix
composite
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Interface
Matrix Fiber
C
Representative
volume cell
• Fabricated by liquid phase infiltration.
•Continuous unidirectional tungsten fibers were packed in
ceramic tubes to the desired fiber content.
•A slug of copper was placed above the fiber bundle, and
the assembly was placed in a furnace and heated to 1478
K (2200 °F) for 1 hr in either a vacuum or hydrogen
atmosphere.

3. Applications of W/Cu composite
• High Temperature aircraft- high creep resistant
• Rocket engine turbine
• High strength electrical conductor- strength by resistivity ratio 10
times higher than other

4. Takes initial
configuration
Calculates
potential
Obtain Force
Finds
velocity and
position
Ends if last
timestep is
reached
M D Simulation
Velocity-verlet integration with 2
fs timestep
v(t+∆t)=v(t)+a(t)∆t
r(t+∆t)=r(t)+v(t)∆t+1/2a(t)∆t
Checks timestep

5. Simulation models and Parameters
Copper atom
Tungsten atom
Tungsten fiber reinforced copper nanowire
r=5Å
Copper nanowire before reinforcement
r=20Å
• Critical fiber length Lc = (σf*d)/2Tc = 2.2 nm{(16*5)/(2*18)= 2.2 }
•Rule of mixture: σc=σf*Vf +σm*Vm
Kc=Kf*Vf+Km*Vm
• There is insolubility between tungsten and copper

6. Results and discussions
at 0.5%/ps strain rate
T= 300 K
(Gpa)
(Å/ Å)
Engineering stress strain plot
• Increased in yield strength observed
• Presence of Tungsten Fiber delays the onset of necking

7. VMD snapshots at strain of 150 %
A B
Experimental Engineering strain stress curve
(Review David L. McDanels, Lewis research centre,
NASA, Tungsten Fiber Reinforced Copper Matrix
Composites)
Comparison with experiment

8. Conclusions
• Reinforcement of Tungsten fiber increased the strength of the
Cu matrix
•The yield strength of composite is ~4.5 Gpa
• The high strength to resistivity ratio makes it usable as high
strength electrical conductor
• Use of this composite as structural component in space craft
reduces its weight high strength by weight ratio

9. Refernces
[1] He, L.H., Lim, C.W., Wu, B.S., 2003. A continuum model for size-dependent
deformation of elastic films of nano-scale thickness.Int.J.Solids Struct.41 (3–4), 847–
857
[2] University of Virginia, MSE 4270/6270: Introduction to Atomistic Simulations,
Leonid Zhigilei
[3] http://lammps.sandia.gov/doc/Manual.html
[4] R.A. Johnson, Physics Rev, B37, 1988, 6121
[5] http://www.crystallography.fr/mathcryst/twins.htm
[6] Jeong-Won Kang and Ho-Jung Hwang, Mechanical deformation study of copper
nanowire using atomistic simulation, Nanotechnology 12 (2001) 295–300
[7] P.R. Subramanian and D.E. Laughlin, Cu-W (Copper Tungsten), Indian Institute of
Metals, Calcutta, 1991, pp. 76-79
[8] Dalvid-L. McDanels, Tungsten Fiber Reinforced Copper Matrix Composites,
NASA Technical Paper 2924, 1989
[9] David L. McDanels, Robert W. Jech, andJohn W. Weeton;
Lewis Research Center Cleveland, Ohio, Stress-Strain Behaviour Of Tungsten-
Fiber-Reinforced Copper Composites, NASA TN D-1881