Two- and three-dimensional carbon-carbon composites with either resin-derived matrix or CVI matrix were joined to Cu-clad-Mo using active Ag-Cu braze alloys for thermal management applications. The joint microstructure and composition were examined using Field-Emission Scanning Electron Microscopy and Energy-Dispersive Spectroscopy, and the joint hardness was characterized using the Knoop microhardness testing. Observations on the infiltration of the composite with molten braze, dissolution of metal substrate, and solute segregation at the C-C surface have been discussed. The thermal response of the integrated assembly is also briefly discussed

Asthana, R.

Shpargel, T.P.

Singh, M.

NASA Technical Reports Server

Daytona Beach Conference, Abstract, American Ceramic Society 
 
Bonding and Integration of C-C Composite to Cu-Clad-Molybdenum for 
Thermal Management Applications 
 
 
R. Asthana1 ∗, M. Singh2,and T.P. Shpargel3 
 
1Department of Engineering and Technology 
University of Wisconsin-Stout 
Menomonie, WI 54751, USA 
 
2Ohio Aerospace Institute 
NASA Glenn Research Center 
 Cleveland, OH 44135, USA 
 
3ASRC Aerospace 
Cleveland, OH 44135, USA 
 
 
 
 
Abstract 
 
Two- and three-dimensional carbon-carbon composites with either resin-derived matrix or CVI 
matrix were joined to Cu-clad-Mo using active Ag-Cu braze alloys for thermal management 
applications. The joint microstructure and composition were examined using Field-Emission 
Scanning Electron Microscopy and Energy-Dispersive Spectroscopy, and the joint hardness was 
characterized using the Knoop microhardness testing. Observations on the infiltration of the 
composite with molten braze, dissolution of metal substrate, and solute segregation at the C-C 
surface have been discussed. The thermal response of the integrated assembly is also briefly 
discussed.  
 
* Currently with ASRC Aerospace, Cleveland, OH 
https://ntrs.nasa.gov/search.jsp?R=20080033105 2019-08-30T05:07:50+00:00Z
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R. Asthana*, M. Singh**, and T.P. Shpargel***
* University of Wisconsin-Stout
Menomonie, WI 54751
**Ohio Aerospace Institute
NASA Glenn Research Center
Cleveland, OH 44135
*** ASRC Aerospace
NASA Glenn Research Center
Cleveland, OH 44135
Bonding and Integration of C-C Composites           
to Copper-Clad-Molybdenum for                      
Thermal Management Applications
2
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Overview
• Introduction and Background
• Experimental Procedures
– Materials and Brazing
– Characterization (Microstructure, Microhardness) 
• Results and Discussion
– Microstructure and Composition of Joints
– Microhardness
– Residual Stress and Thermal Considerations
• Concluding Remarks
• Acknowledgments
23
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Thermal Properties of Some Typical 
Thermal Management Materials
Temperature
(K)
0 500 1000 1500 2000 2500
S
pe
ci
fic
 T
he
rm
al
 C
on
du
ct
iv
ity
[(W
/m
K
)/(
g/
cm
3 )
]
0
20
40
60
80
100
120
140
Al BeCu Ti
Al
W
Be
Mo
Cu
Ti
Nb
Gr/Al
(In Direction Of Fiber)
Gr/Cu
(In Direction Of Fibers)
Operating Temperature Can Limit Material Choices
4
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Thermal Management Material Properties
Carbon-Carbon Composites Provide Tremendous Advantage 
and Excellent Benefits for Thermal Management
From: “High thermal conductivity composites for passive thermal management," 
Metal Matrix Composites Information Analysis Center -Current Highlights, 8, 2 (1988). 
35
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Application of Carbon-Carbon Composite 
Materials in Thermal Management Applications
Thermal conductivity of C/C composites strongly depends on the 
fiber type, architecture, and composite processing technology   
Source: K. Kearns, Composites, ASM Handbook, 
Vol. 21 (2002) 1067-1070.
• High modulus, high conductivity pitch based carbon fibers can be used to improve 
the thermal properties of C-C composites.  
Source: Comprehensive Composite Materials, 
Vol. 4, 3 (2000).
6
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Active Metal Brazing of Titanium to C/C 
Composites for Heat Rejection Systems
• Recently, we had joined C-C composite 
to Ti tubes for lightweight heat 
exchanger applications.
• Both direct bonding using braze layers 
and indirect bonding using a porous 
carbon foam (saddle material) and braze 
layers were employed.
• Excellent bonding of active braze to 
foam, C-C Composite, and Ti Tube 
occurred. 
• Failure always occurred in Poco HTC 
(Saddle Material) indicating that bond 
strength exceeded the fracture strength 
of foam.
1. M. Singh et al, Mater. Sci. Eng. A (in press).
2. M. Singh et al, Mater. Sci. Eng., A 412, 2005, 
123-128.
3. G.N. Morscher et al, Mater. Sci. Eng., A 418(1-
2), 2006, pp 19-24.
Large difference in CTE of C-C and 
metals lead to large residual stresses
0
1
2
3
4
5
6
7
8
9
0 0.2 0.4 0.6 0.8 1
ΔαΔT, %
B
S
T 
S
he
ar
 S
tr
en
gt
h,
 M
Pa
C/C to C/C (CuSil ABA)
SBond Solder
CuSil ABA
TiCuSil
Δα = α (Ti) – α (C/C)
ΔT = T (liquidus ~ processing) – 25oC
0
5
10
15
20
25
Ticusil Ticuni Gold-ABA Gold-
ABA-V
Copper-
ABA
C-C Copper Titanium
Th
er
m
. C
oe
ff.
 o
f E
xp
an
. (
*1
0^
-6
/C
)
47
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Testing of Brazed Joints in Woven K1100 and  
P120 C/C Facesheet/Foam/Ti Tube
Specimens with different tube-foam contact areas were  fabricated in 
order to vary braze contact area and stress applied to joints
Tube on flat Tube in shallow 
trough
Tube in deep 
trough Highest contact 
area, lowest 
stress on joint
Lowest contact 
area, highest 
stress on joint
Start of 
Poco
failure in 
bending
Debond in outer ply 
of C/C
After Tension After shear
M. Singh et al, Mater. Sci. Eng., A 2008 (in the press)
8
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Why Copper Clad Molybdenum was chosen as a 
Thermal Management Material ?
4
5
6
7
8
9
10
11
12
0 5 10 15 20 25 30 35 40 45
% Cu Thickness per side
CT
E,
 p
pm
/K
150
160
170
180
190
200
210
220
230
240
0 5 10 15 20 25 30 35
% Cu Thickness per Side
Th
er
m
al
 C
on
du
ct
iv
ity
, W
/m
.K Thermal Conductivity of Cu-clad-Mo (x-axis)
0
50
100
150
200
250
300
0 5 10 15 20 25 30 35 40 45
% Cu Thickness Per Side
Th
er
m
al
 C
on
du
ct
iv
ity
, W
/m
.K
Thermal Conductivity of Cu-Clad-Mo (y-axis)
(from Electronic Materials and Processes 
Handbook, C.A. Harper, McGraw-Hill, 2003)
• Copper has excellent thermal 
conductivity (K for OFHC Cu: 401 
W/m.K).
• CTE of Cu is high (16.5 ppm/K). 
Difficulty in joining to ceramic 
substrates.
• Low annealing temperature of Cu 
causes softening at moderate heat 
input.
• Cladding Mo with Cu lowers CTE 
and promotes thermoelastic
compatibility with ceramics.
• Some loss of thermal conductivity 
(Mo: 138 W/m.K, Cu: 401 W/m.K).
• Small weight penalty (density of 
Cu: 8,900 kg.m–3, density of Mo: 
10,280 kg.m–3).
59
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Objective
• Develop brazing approaches for 2D and 3D C-C 
composites with resin and CVI matrices to Cu-clad-
Mo using active braze alloys.
• Characterize the joint microstructure, composition, 
and microhardness behavior.
10
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Experimental Procedure: Materials and Properties 
• 2-D and 3-D C-C composites (Resin +CVI Carbon matrix) –
Goodrich Corp., CA.
• C-C composites (Resin derived matrix) – C-CAT, Inc., TX. 
• Cu-clad-Mo plates (Cu-Mo-Cu ratio: 13%-74%-13%) –
H.C. Starck, Inc., MA.
• Active braze alloy (ABA) powders – Morgan Advanced Ceramics, CA.
Composition and Properties of Brazes
2192818.533929285780900Ticusil®
(68.8Ag-26.7Cu-4.5Ti)
1804218.534627183780815Cusil-ABA®
(63Ag-35.3Cu-1.75Ti)
K, 
W/m.K
% 
El.
CTE, 
×10-6 C-1
UTS, 
MPa
YS, 
MPa
E, 
GPa
TS, °C
TL, °C
Braze (composition, %)
E: Young’s modulus, YS: yield strength, UTS: tensile strength, CTE: coefficient of thermal expansion, %El: percent elongation,
K: thermal conductivity
611
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• Substrates cut into 2.54 cm x 1.25 cm x 0.25 cm plates and 
ultrasonically cleaned in acetone for 15 min. 
• Braze powders mixed with glycerin to dough-like consistency 
and braze paste manually applied to C-C surface. 
• Assembly heated under vacuum (~10-6 torr) to 15-20°C above 
braze TL. After 5 min. soak, slowly cooled (~5ºC per min.). 
• Brazed joints mounted in epoxy, ground, polished, and 
examined using optical microscopy and Field Emission 
Scanning Electron Microscopy (Hitachi 4700) coupled with 
EDS.
• Microhardness (Knoop indenter) on Struers Duramin-A300 
machine (200 g load, 10 s). Four-to-six scans across each 
joint.
Experimental Procedure
12
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C-C Composite/Cu-Clad-Mo Joints for Thermal 
Management Applications
• Resin-derived C-C 
composites brazed to Cu-
clad Mo using active braze 
alloys (ABA).
• Good metallurgical bonding 
at joints, with some 
dissolution, diffusion, and 
solute redistribution. 
• Ti segregated at C-C surface. 
Cu-ABA joints displayed the 
largest Ti concentrations at 
joint. 
• Microhardness gradients 
exist at joints.
• C-C/Cu-clad Mo systems may 
have potential for thermal 
management applications.
75umC-C Cusin
Cu-clad Mo
Cu-cladding
Carbon-
carbon
1
Cusin
Cu-rich phase
Ag-rich phase
2
3
4 5 6
1
C-C 
75umCu-clad Mo
Mo Cu
Ticusil
CC
C-C Ticusil Cu-clad Mo
C-C
Ticusil
Cu-rich 
phase
1 23 4
6 Cu(Ag)
Ag(Cu,Mo)
Cu-clad Mo side
2
3
4
5
Ag-rich phase
M. Singh, R. Asthana, T. Shpargel, Mater. Sci. Eng., A 452-453, 2007, 699-704
713
National Aeronautics and Space Administration
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(a)
3-D C-C Composite/Cu-clad-Mo Joint 
P120/Cusil-ABA (a)
200 μm
Cu-clad-Mo
3D C-C composite
Ticusil
Braze infiltration
Braze: Ticusil (b)
3D C-C composite
Cu-clad-Mo
Cusil-ABA
100 μm
Braze: Cusil-ABA
• Braze penetration to several hundred micrometers in 5 min.
• No effect of fiber ply orientation on infiltration. 
• Improved wetting by Ti in braze facilitated infiltration. 
• No reaction choking and flow cessation from carbide forming reactions. 
• Extensive infiltration of C-C consistent with sessile-drop tests  
(complete disappearance of drops in porous carbon!). 
14
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3(a)
Cu-clad-Mo
Cusil-ABA
C-C
C-Ag (Mo,Ti)
Ti-C-Ag-Cu (Mo)
Ag-Cu (C,Mo,Ti)
Ag-Cu-Ti
3(b)
10 μm
Cu-Ag (Mo,Ti)
Ag-Cu (Mo,Ti)
Cu-Ag (Mo,Ti)
Cu-Mo-Ag (Ti)
Mo (Ti,Ag,Cu)
20 μm
3(c)
3-D C-C composite/Cusil ABA/Cu-clad-Mo joint 
• High concentrations of Ti at interface. 
• Two-phase eutectic structure in braze (Ag-rich light-
grey and Cu-rich dark grey). 
• No melting of clad layer (M.P. of Cu: 1086ºC)
• Possible formation of titaium carbide (Ti+CÆ TiC, 
ΔG = -171.18 kJ at 850°C). 
• Sub-stoichiometric carbides (TiC0.95, TiC0.91, 
TiC0.80, TiC0.70, TiC0.60 and TiC0.48) may also form.
8.0940.00089.4692.4370.000Point 4
94.8350.2813.8810.3280.675Point 3
8.8130.9415.20349.91235.131Point 2
2.1160.7230.0000.69396.468Point 1
AgMoCuTiCLocation
815
National Aeronautics and Space Administration
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C-Ag (Mo,Ti)
C-Ag (Mo,Ti)
C-Ag (Mo,Ti)
5(a)
Cu-Ti-Ag (C)
Ag-Cu (C,Ti)
Carbon (Cu,Ti)
Ag-Cu (C,Ti,Mo)
5(b)
10 μm
Mo-C (Cu,Ti)
Mo-C-Cu 
(Ti,Ag)
Cu-Ag-Ti (C,Mo)
Ag-Cu-C (Ti,Mo)
+1
+2
+3
+4
+5
+6
10 μm
5(c)
3-D C-C composite/Ticusil/Cu-clad-Mo joint 
• Some dissolution of carbon in 
braze (possibly due to higher 
temperature of Ticusil).
• Carbon also detected within 
the Cu-clad-Mo region.
2.0300.55316.69754.48426.237Point 6
0.2620.2311.1830.26498.060Point 5
88.6230.3822.77610.0841.852Point 4
14.0570.23675.6230.3680.000Point 3
92.6270.5084.5400.2282.097Point 2
5.1540.31481.0978.0905.345Point 1
AgMoCuTiCLocation
16
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TicusilCu-clad-Mo C-C
6(a)
Cu-Ag-Ti
C (Ag,Mo,Ti)
C-Cu (Mo,Ag,Ti)
Ag-Cu (C)
6(b)
13 μm Mo-C-Cu (Ti,Ag)
Ag-Cu (C, Mo)
Cu-Ag-Ti (C, Mo)
6(c)
13 μm
C-C composite/Ticusil/Cu-clad-Mo joint 
(resin-derived composite)
• Cracks in composite (low inter-
laminar shear strength).
• Braze displays eutectic structure 
with Ag- and Cu-rich phases. 
• Precipitation of Ag-rich phase on 
C-C and Cu-clad-Mo surfaces.
• A small amount of Cu detected 
within the C-C composite.
1.2681.13618.7660.52778.303Point 4
0.2180.1980.0000.11299.472Point 3
86.9730.4609.8740.4952.198Point 2
14.6170.42277.5596.6030.799Point 1
AgMoCuTiCLocation
917
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C-C (O).Ticusil.Cu-Clad-Mo
0
50
100
150
200
250
300
350
400
35.6 35.8 36 36.2 36.4 36.6 36.8 37 37.2 37.4
Distance, mm
HK
Molybdenum
C-C
Ticusil
+
Cu cladding
C-C (N.O.).Cusil-ABA.Cu-Clad-Mo
0
50
100
150
200
250
300
350
400
450
35 35.2 35.4 35.6 35.8 36 36.2 36.4 36.6
Distance, mm
H
K
Molybdenum Cu cladding 
+ 
Cusil-ABA 
C-C
C-C (resin-derived).Ticusil.Cu-Clad-Mo
0
50
100
150
200
250
300
350
35.7 35.8 35.9 36 36.1 36.2 36.3 36.4 36.5 36.6 36.7
Distance, mm
H
K
Molybdenum
C-C
Cu cladding
+ Ticusil
Knoop Hardness across Brazed Joints
• No effect of fiber ply orientation and composite type (CVI vs resin-derived) on HK within the 
braze region. 
• HK of Mo substrate is ~200-330;  HK depends on braze type: Ticusil (4.5%Ti) has higher HK 
(~85-200) than Cusil-ABA (1.75%Ti) (~50-150). 
• Some effect of larger residual stresses in Ticusil because of its higher joining temperature. 
18
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Strain Energy in Brazed Joints
• Less strain energy develops in Cusil-ABA joints than in Ticusil joints.
• Strain energy C-C/Ticusil/Cu-clad-Mo joints is 37.5 mJ.
• Ductile braze and Cu cladding prevented failure.
• Lower strain energy in comparable joints of Cu-clad-Mo with SiC-SiC.
(J.-W. Park, P. F. Mendez and T. W. Eagar, Acta Mater., 2002, 50(5), 883-899)
Large strain energy Æ Greater tendency for fracture
0
10
20
30
40
50
60
1 2
S
tr
ai
n 
E
ne
rg
y,
 m
J
Cusil-ABA Ticusil
Ti
Inconel
Cu-clad-
Mo
C-C
SiC-SiC
SiC-SiC
C-C
Ti
Inconel
Cu-clad-
Mo
10
19
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Estimation of Thermal Resistance in Brazed Joints
Effective thermal resistance (1-D steady-state conduction)
Reff = Σ(Δxi/Ki)
(Δxi: thickness Ki: thermal conductivity)
• C-C/Cu-clad-Mo joints have 22% lower thermal resistance than C-C.
• There is some weight penalty in joining C-C to Cu-clad-Mo (39% 
increase in density). 
• Potential benefit to join C-C to Cu-clad-Mo in thermal management 
systems. 
0.00E+00
5.00E-05
1.00E-04
1.50E-04
2.00E-04
2.50E-04
3.00E-04
1 2
Th
er
m
al
 R
es
is
ta
nc
e,
 m
2.
K/
W
CompositeComposite/Cu-clad-Mo Joint
C-C
CVI SiC-SiC
N24-C
HiPerComp 
(GE)
ZrB2-SiC
Braze: Ticusil, 100μm
Substrates: 2.5 mm each 
20
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Concluding Remarks
• C-C composites with CVI and resin-derived matrices were 
brazed to Cu-clad-Mo using active braze alloys. 
• SEM and EDS revealed sound bonding and Ti segregation at 
interface and no evidence of extensive chemical attack of C-C. 
There was limited redistribution of alloying elements. 
• De-lamination in resin-derived C-C was observed due to its low 
inter-laminar shear strength (ILSS). Extensive braze infiltration 
of inter-fiber channels occurred in 3D composites. 
• Sharp hardness gradients occurred at Cu-clad-Mo/braze 
interface. Ticusil exhibited greater hardness (~85-250 HK) than 
Cusil-ABA (~50-150 HK). This may be due to higher Ti content of 
Ticusil (4.5% Ti) than Cusil-ABA (1.75% Ti). 
• C-C/Cu-clad-Mo joints may have ~22% lower thermal resistance 
compared to C-C composites. 
11
21
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Acknowledgement
• Ceramics Branch, NASA Glenn Research Center, Cleveland, 
OH for support to R. Asthana.


Bonding and Integration of C-C Composite to Cu-Clad-Molybdenum for Thermal Management Applications

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