Sublimation CI SCI-2

CERAMICS
INTERNATIONAL
Available online at www.sciencedirect.com
Ceramics International 41 (2015) 13751–13758
Sublimation and oxidation zone ablation behavior
of carbon/carbon composites
Shameel Farhana
, Rumin Wanga,n
, Kezhi Lib
, Chuang Wangb
a
School of Science, Northwestern Polytechnical University, Xi’an 710072, China
b
School of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China
Received 21 July 2015; received in revised form 31 July 2015; accepted 7 August 2015
Available online 18 August 2015
Abstract
Three-dimensional carbon/carbon (C/C) composites comprising four reinforcement directions (4D) were fabricated using intermediate modulus
carbon fibers and densified using a hybrid process. This consists of a pre-densification step using a thermal-gradient chemical vapor infiltration
process followed by a high-pressure pitch impregnation and carbonization process. The specimens machined along Z-axis of the preform
architecture were tested in an arc plasma heater for studying its ablation behavior at different temperatures. Regimes from ultra-high temperature
(4750 K) sublimation to high-temperature (2467 K) oxidation zones were created by varying the mass flow rate of secondary air in the heater. The
ablation rate showed a progressive increase as the environment changed from oxygen-lean sublimation to oxygen-rich oxidation conditions while
the back-face temperature showed a similar temperature profile during the plasma exposure period. The thermal diffusivity value decreased with
the rise in temperature till 1173 K and later on became fairly flat till 1523 K and onwards. In the compression test, 4750 K exposed specimen
showed toughening in the plasma-affected zone and crushed with shear mode from the opposite face while the 2467 K exposed specimen showed
end brushing in the plasma heat-affected face with a lower residual strength and Young’s modulus.
& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Keywords: E. Thermal applications; Carbon/carbon composites; Plasma arc-heater; Ablation; Oxidation
1. Introduction
Carbon/carbon (C/C) composites are materials of choice in
aerospace industry due to their outstanding thermostability and
thermomechanical properties at a very high temperature [1–5].
C/C composites were originally used on ablative structures
(e.g., rocket nozzles, re-entry nose tips & leading edges) in
which the material has to endure high thermal gradient and is
mainly ablated by some gasification processes like oxidation
and sublimation [6]. The re-entry conditions vary with the type
of mission: temperature up to 5000 K and pressure up to
100 bar, and a heat flux received by the protection ranging
from 0.1 to 500 MW/m2
[7]. Under such conditions, a
considerable part of the heat flux is consumed by mass
transfer, which has two principal forms: oxidation and
sublimation. These phenomena are grouped under the generic
name of ablation [8]. By definition, ablation is a process of
elimination of a large amount of thermal energy by sacrificing
a portion of mass of the ablative material. General physio-
chemical reactions containing this process are phase changes,
conduction, convection, radiation, diffusion and exothermic/
endothermic chemical reactions [9]. Chemical reactions play a
significant role in establishing ablation rates of most of the
resultant material-environment combinations. Ultra high tem-
perature ceramics are the potential candidates for thermal
protection of reentry vehicles because of their very high
melting points. The major hurdle in the development of these
materials is that their manufacturing techniques are not mature
until now [10]. High density of the material as well as
machining problems is another reason to search for alternative
www.elsevier.com/locate/ceramint
http://dx.doi.org/10.1016/j.ceramint.2015.08.043
0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
n
Correspondence to: Department of Applied Chemistry, School of Science,
NWPU, Youyi West Road 127, Xi’an 710072, Shaanxi, China.
Tel.: þ86 29 88492947.
E-mail addresses: shameelfarhan@yahoo.com (S. Farhan),
rmwang@nwpu.edu.cn (R. Wang).

materials overcoming aforementioned problems with addi-
tional advantages apart from the uniform thermo-mechanical
properties, low erosion and high thermal stability. The material
studied in this research is three-dimensional and four-
directional (4D) in structure. The 4D C/C composites are well
known for their excellent thermo-physical and thermo-
mechanical properties in short-term, high-temperature applica-
tions [11–14]. Due to the high interlaminar shear strength, they
exhibit high performance with respect of shape stability and
anti-ablation [15].
Many experimental characterizations of C/C composites
have been reported in literature [16–19]. The oxyacetylene
flame ablation and plasma arc ablation are the most widely
used methods to study the ablation behavior of C/C composites
[20–24]. Oxyacetylene flame does not simulate the actual
reentry conditions due to limited heat flux and flow species
[25]. Only plasma arc heater can produce nearly similar reentry
conditions. Moreover, these experiments include micro, meso
and macroscopic observations of the ablated surface and
measurements of the recession rates. The ablated surface
morphology generally consists of fiber denudation and block
denudation and the recession rates can be expressed in terms of
the linear erosion rate and the mass ablation rate. The testing
temperature is around 3200 K similar to the temperature in the
nozzle of solid rocket motor.
To the authors’ knowledge, no one has done such kind of
work in which operating parameters of an arc heater were
changed with regard to chemical reactivity of C/C composites.
The purpose of this research is to differentiate the two main
chemical reaction regimes: oxidation dominant and sublima-
tion dominant and compare the effects of these regimes on the
ablation behaviour of a 4D C/C composite. The temperature
was adjusted by controlling the mass flow rate of the
secondary air (plasma cooling gas) so that the oxygen-rich
high temperature ($2500 K) and oxygen-lean ultra-high
temperature ($ 4500 K) were created in the plasma flow
field. Moreover, the effect of plasma stream temperatures,
stagnation enthalpies, gaseous velocities, and cooling (second-
ary) air flow rate on the ablation behavior of the 4D C/C
composite was also studied. The stagnation-point ablation rates
were measured with different mix ratios of primary and
secondary air working as the test gas. Air was chosen as a
testing media for the simulation of the reentry condition. Air
having a mixture of O2 and N2, dissociates into N, O, NO,
when it passes through the shock wave created arc in the
plenum chamber of arc heater. The composite studied was
prepared by a hybrid process and six samples of similar
density and fiber orientation were machined out for testing. To
examine the effect of hostile environment on the virgin
material, back-face temperature and the residual compressive
strength of the two specimens that experienced extreme
conditions were also tested. The two extreme conditions were
ultra-high temperature (4750 K) oxygen-lean and high tem-
perature (2467 K) oxygen-rich environment respectively. The
resulting back-face temperature, crushing behavior and load–
displacement plot were also discussed in relation to the
ablation test conditions.
2. Experimental
2.1. Preform fabrication
A 4D preform was fabricated by the insertion of stiffened
carbon rods in four directions in an orthogonal plane. TC 42S
carbon fiber (Tairyfil Co., China) bundles with 5.7 μm
diameter, 5150 MPa ultimate tensile strength and 290 GPa
Young’s modulus were used in the dry weaving process.
Multiple fiber bundles were combined and passed through a
8–15% binder solution in a standard pultrusion machine. The
binder can be any kind of organic polymer like polyvinyl
chloride, polyvinyl alcohol, epoxies and resins that are used in
the manufacture of advanced fiber reinforced composites. Here
solid novolac dissolved in organic propanol was chosen as a
novel choice. The excessive resin was squeezed by passing
through a series of nozzles and the coated rods were dried in a
tube-heating oven. The maximum fiber preheating and the
pultruded rods post-treatment temperatures were 653 K (opti-
mum for removing coatings from the carbon fiber) and 523 K
(curing temperature of novolac), respectively. The diameter of
the pultruded rod was controlled within 1.0 to 1.30 mm
depending upon the number of tows and weaving geometry
requirements. After rigidization, novolac binder in the pultrur-
ods was about 5% by weight. Fiber volume fraction (Vf) was
maintained in the range of 8–9% in the XY-plane and 13–14%
in the Z-axis. Total Vf of the preform was about 40% and the
bulk density was almost 0.69 g/cm3
. Further details about the
preform employed can be found in [26,27].
2.2. Densification process
The preform was densified using a hybrid process which is a
combination of two processes. A pre-densification step with a
thermal-gradient chemical vapor infiltration (TCVI) process
and a high-densification using a high pressure pitch impreg-
nation and carbonization (HiPIC) process. The preform was
first high temperature (HT) treated at 1873 K to convert the
fiber coating and resin into the carbon. The HT process was
conducted at a very slow rate with the aid of graphitic holding
plates to avoid the collapse of the preform. Pyrolytic carbon
from the natural gas (98% CH4, 0.3% C3H8, 0.3% C4H10,
0.4% other hydrocarbon, 1% N2) was deposited on the carbon
fibers in a TCVI furnace at temperature range of 1350–1450 K
[28]. At a deposition rate of 0.5 mm/h, a bulk density of
1.70 g/cm3
was achieved in 80 h. It was further increased to
1.86 g/cm3
by three successive HiPIC cycles. Intermediate heat
treatment at 2500 K after TCVI process was used for pore
opening, graphitization and strength enhancement [29]. High
softening (HS) pitch (399 K softening point, 1.30 g/cm3
density, 490% carbon contents, 4.5% hydrogen, 455%
carbon yield) was poured on the pre-densified C/C composite
under vacuum and stabilized for 5 h at 573 K. As shown by
studies [30] on wetting and impregnation of carbon fibers by
HS pitches, no impregnation of the inter-filamentary porosity
occurs even at high temperature and therefore, pressure turns
out to be necessary for the densification of C/C composites. It
S. Farhan et al. / Ceramics International 41 (2015) 13751–1375813752

was further carbonized at 1100–1200 K and 80 MPa isostatic
pressure.
2.3. Characterization
2.3.1. Density and porosity
The geometric density of 4D C/C specimens
(ø¼22 mm Â 50 mm) after final HT treatment was measured
by the ratio of mass of the sample to the total apparent volume.
True density and apparent porosity of carbon foam were
examined by helium gas displacement pycnometer (Pentapyc
5200e Quantachrome Instruments, Florida, USA). True density
is the mass per unit volume of material, which exclude all
voids or pores. Open porosity was calculated using the
following expression:
%P ¼
ρt Àρa
ρt

Â 100 ð1Þ
where %P is the bulk open porosity, ρt and ρa are true and
apparent densities of the samples respectively. The true density
of the composite was found to be 1.9070.01 g/cm3
while the
final open porosity of the composite was 3.2570.25%.
2.3.2. Electric arc plasma testing
The 4D C/C composite block was cut along the Z-axis of the
fiber architecture forming a cylindrical geometry with outer
diameter of 22.5À0.5
mm and length of 50 mm. The length (or
thickness) of the specimens is not so important because only
the blunt face was exposed to air plasma and thus, the exposed
area was kept fixed at 3.97 Â 10À4
m2
. Fibers in the XY-plane
were oriented in 01 (U-direction), þ601 (V-direction) and
À601 (W-direction) angles whereas Z-directional fibers were
along the Z-axis. In the testing, Z-axis fibers were at 901 to the
blunt face (face exposed to plasma stream). The ablation
experiments were performed on a Huels type arc heater. Two
tandem cylindrical electrodes were separated by a central
copper tube and insulated from each other. Primary air was
injected tangentially to the wall of the heater from four
different points in a manner to encircle the plasma jet along
the centerline and to stabilize it with the minimum contact with
the inner surfaces. A magnetic coil was used on the anode to
rotate the arc termination and prevent arc backfire to the rear
plug. The heater was ignited by a high-voltage breakdown with
Ar gas filling the chamber. Within one second, after the arc
breakdown, the gas supply was switched from Ar to air. The
plasma expanded as it passed through a converging–diverging
nozzle to a low supersonic Mach number. The secondary air
was injected into the upstream end of the constrictor at various
flow rates for the adjustment of final temperature and velocity
of spurting plasma stream. To ensure quasi-one dimensional
heat flow, a silica/phenolic holder was used to hold and protect
the samples from side-wall heating at a length of 15 mm from
the exposed face. The planar surface of the specimen and the
holder were flushed and grinded using SiC emery papers with
360 down to 1200 grit. The following parameters listed in
Table 1 were either fixed or varied for the study of their effect
on the ablation behavior of the 4D C/C composite.
A small hole (ø¼3 mm Â 35 mm) was drilled in the speci-
mens from the backside for the insertion of a thermocouple.
Because C/C composites have good electrical conductivity, the
compacted mineral-insulated metal-sheathed, K type thermo-
couple with a range of À73 to 1550 K was used following
ASTM E235 M-23 test method. The distance between the
thermocouple and the exposed surface was fixed at almost
15 mm. The centers of the plasma and the specimen were
aligned horizontally. A microbalance (1 mg precision) and a
0.1 mm precise caliper gauge were used for the pre- and post-
test evolution of samples. After attaining the required condi-
tions of static chamber pressure and heat flux, the sample was
moved into the sputtering plasma flow with the help of
pneumatically-drive trolley. After the test, ablated mass was
divided by the exposed surface area and test duration and the
results were expressed with a unit of kg/m2
-s. Fig. 1 shows the
schematic of the experimental set up fitted with a specimen and
a back-face thermocouple.
2.3.3. Thermal diffusivity
The thermal diffusivity of 4D C/C composite cut into disk
geometry (ø¼12.5 mm Â 2.5 mm) was measured by the flash
diffusivity method, which basically consists of subjecting one
side of a sample to a single laser flash and then monitoring the
transient temperature response on the other side. A Netzsch
LFA 457 Micro-Flash instrument with the guidelines of ASTM
E-1461 standard was operated from room temperature to
1250 1C under Ar atmosphere. The uncertainty of the mea-
surements was 75%.
2.3.4. Compression after ablation (CAA)
The compression-after-ablation (CAA) [26] of the material
was studied using the SANS CMT 5105 (100 kN) mechanical
testing machine. The vertical moving speed of the crosshead
was set at 0.5 mm/min with the load and displacement being
recorded and were in the direction parallel to Z-axis carbon
fiber rods. The specimens were cut using a diamond saw to a
height of about 30 mm. To create a smooth surface, thin layers
of ablated surface were removed using 600 sand papers. The
specimens were dried in a drying oven at 110 1C for 120 min
before the compressive tests. The compressive strength was
calculated according to the following equation:
σc ¼
Ρ
Α
ð2Þ
where P was the maximum loading of fracture (N); A was the
cross-sectional area of the specimen (mm2
).
3. Results and discussion
3.1. Electric arc plasma testing
Fig. 2 shows the macro-morphologies of the samples after
exposure to high-energy reactive air plasma test in an ambient
atmosphere. The recession rates along with different arc heater
parameters are summarized in Table 2. The ablation rate and
temperature as a function of the ratio of secondary to primary
S. Farhan et al. / Ceramics International 41 (2015) 13751–13758 13753

air are plotted in Figs. 3 and 4. The ablation rate came out to be
2.17 kg/m2
-s for the initial flow ratio of 1.01, and increased to
2.62 kg/m2
-s when the ratio exceeded to 2.62. Such an
increase was attributed to the strong oxidizing condition in
the plasma flow resulting from the increase in mass flow rate of
the secondary air. The flow enthalpy of the plasma stream also
decreased with the increase in secondary air flow rate. The
back-face temperatures of the specimen 1 and 6 were recorded
during the ablation testing to see the effect of ultra-high
temperature (4750 K) and high temperature (2467 K) environ-
ments on the back-face temperature. From specimen 1 to 6, the
temperature and stagnation enthalpy gradually decreased from
4750 to 2467 K and 5750 to 2819 kJ/kg, respectively, by
increasing the mass flow rate of the secondary air. The
secondary air was injected upstream before the nozzle and
acted as a cooling gas. The ablation rate increased with
decreasing the temperature of plasma stream, which was
nearly in a reverse order. The highest ablation rate of
2.62 kg/m2
-s was observed in case of the lowest temperature
of 2467 K, the highest air mass flow rate (15.8þ41.42 g/s) and
the plasma stream velocity of 630 m/s. Virtually all oxygen in
the plasma stream reacted with the carbon atoms, irrespective
of the heating rate, to form CO2 and CO when the temperature
was r3000 K. The enthalpies of these species are negative
with respect to that of un-dissociated air. In specimen 6, the
conditions were favorable for oxidation reaction dominance
(excess secondary air) and mechanical denudation due to the
shear forces of high plasma velocity. Macro-morphology of the
specimen 6 also revealed excessive oxidation pits on the
Table 1
Arc-heater parameters during sublimation and oxidation zone ablation testing of 4D C/C composites.
Fixed parameters Variable parameters
Primary air flow
rate (g/s)
Distance of
specimen (mm)
Ablation
time (s)
Secondary air flow
rate (g/s)
Hot chamber
pressure (bar)
Thermal enthalpy
(kJ/kg)
Velocity of plasma
stream (m/s)
Temperature
(K)
15.8570.10 1070.10 15 15.85–38.70 4.2–5.6 3200–5766 574–628 4750–2500
Holder Thermocouple
SpecimenPlasma Stream
Arc Heater
W-direction V-direction
U-directionZ-direction
Fig. 1. Arc heater testing; (a) Schematic of experimental set up and (b) test specimen along Z-axis with reinforcement directions highlighted by bold lines.
5 mm5 mm
Fig. 2. Macro-morphologies of specimens after plasma arc heater test; speci-
men 1 (sublimation regime) to 6 (oxidation regimes) from left to right.
0.8 1.2 1.6 2.0 2.4 2.8
2.0
2.2
2.4
2.6
2.8 Ablation rate
Temperature
Mass flow ratio (Sec. Air / Pri. Air)
Ablationrate(kg/m2-s)
2400
3000
3600
4200
4800
Temperature(K)
Fig. 3. Effect of mass flow ratio on ablation rate and exposure temperature of
plasma arc heater (sublimation to oxidation regimes).

surface and specially at the peripheral area which is compara-
tively weaker against the strong shear forces.
C(s) þO2-CO2 þ395 kJ/mol (3)
CO2þC(s)-2CO–142.5 kJ/mol (4)
CO formed is further reacted with dissociated oxygen which
is very excess in this case, forming CO2 as following:
COþO-CO2þ520.9 kJ/mol (5)
N2 also begins to undergo heterogeneous reactions directly
with the surface to form CN as following:
1/2N2 þC(s)-CN–460.5 kJ/mol (6)
which is further reacted with dissociated oxygen atoms as
following:
CNþ2O-CO2þ1/2N2þ1364 kJ/mol (7)
The resulting energy change due to combustion is therefore
exothermic, giving a positive contribution to the heat trans-
ferred to the surface. Above 3000 K, carbon also started
sublimation in addition to the oxidation [31]. In the specimen
1, the plasma stream temperature was the highest (4750 K)
with a minimum air mass flow (15.89þ16.0 g/s). At such a
high temperature, the oxidation reaction of carbon was
governed by the restricted diffusion rate because of the limited
amount of oxygen [32]. The surface of the specimen 1 was
roughly smooth with a few oxidation pits. It is to be noted that
the plasma stream temperature was 4750 K based on the
testing parameters, the temperature of the ablated surface
was a little lower due to the heat transfer and dynamic thermal
balance existing among the plasma, the specimen and the
environment [33]. We can define the sublimation regime as the
range of conditions where the mass loss due to vaporization
exceeds the diffusion controlled oxidation mass loss rate. It is
noted that at the high surface temperatures, not only do
chemical reactions occur between carbon and oxygen, but also
nitrogen reacts with carbon to form cyanogen (CN) and the
cyano radical CNn
[34]. As the surface temperature rises, the
vaporization rate of atomic and molecular carbon species, such
as C, C2, C3, C4 and C5, all increase exponentially. Note that,
the sublimation process yields appreciably greater amounts of
triatomic carbon gas than monatomic carbon [35].
The major sublimation reactions can be summarized as
following:
3C(s)-C3–753.5 kJ/mol (8)
3C3 þ3N2-6CN–1297 kJ/mol (9)
which is further reacted with limited supply of dissociated
oxygen as following:
CNþO-COþ1/2N2 þ849.5 kJ/mol (10)
The overall energy change in this zone is endothermic. The
effect of these exothermic and endothermic regimes was
further noted in the back-face temperature of the specimens
during ablation testing. The back-face temperature of the
specimen 1 and 6 was 1094 K and 1075 K, respectively. The
difference was not very large as compared with the very large
difference between the hot-face plasma stream temperatures.
The temperature profile is plotted in Fig. 5. The experimental
conditions in the specimen 1 corresponded to the sublimation
regime and in this case, chemical heat flux was negative, while
in the specimen 6, it was positive into the solid which gave
nearly the same back face temperature as that in case of
sublimation regime. In the specimen 1, the effect of ultra-high
temperature on the back-face temperature was lowered by the
dominant sublimation reaction (cooling) whereas in the speci-
men 6, oxidation reaction (heating) reheated the high tempera-
ture conditions. The back-face temperature rose exponentially
at the beginning of the experiment and attained the maximum
growth rate at 4À5 s when a small wiggle in the rising curve
3000 4000 5000 6000
2.0
2.2
2.4
2.6
Ablation rate
Temperature
Enthalphy (KJ/Kg)
Ablationrate(Kg/m2-s)
2400
3200
4000
4800
Temperature(K)
Fig. 4. Effect of stagnation enthalpy on ablation rate of 4D C/C composites
and exposure temperature of plasma arc heater.
Table 2
Summary of arc-heater parameters and resulting recession rates of 4D C/C composites.
Sr.
no
Recession rate (kg/
m2
-s)
Temperature
(K)
Back face
temperature (K)
Enthalpy
(kJ/kg)
Primary air flow
rate (g/s)
Secondary air flow
rate (g/s)
Flow
ratio
Plasma velocity
(m/s)
1 2.17 4750 1094 5750 15.89 16.00 1.01 570
2 2.25 4127 – 4936 15.83 22.50 1.42 587
3 2.31 3531 – 4198 15.80 27.28 1.73 600
4 2.40 3389 – 4033 15.79 29.69 1.88 607
5 2.50 2967 – 3480 15.80 34.86 2.21 617
6 2.62 2467 1075 2819 15.80 41.42 2.62 630

occurred. After that, it started rising with a decreasing growth
rate for the 15 s of test duration and continued 5À7 s after the
completion of the tests. The cooling profiles were different in
the two cases: slow in oxidation leading ablation and fast in
sublimation leading ablation. The small wiggle in the growth
curve occurred at about 373 K due to the moist air superheated
and trapped in the specimens. The melting and sublimation of
the specimen 1 were considered because these phenomena are
significant at a surface temperature greater than 4000 K [36].
At this higher surface temperature, the vaporizing species of C
react with nitrogen into the boundary layer and some of CN
evolved diffuses back to the condensed phase. Also, as before,
CO diffuse back to the surface. All these endothermic reactions
near the surface will reduce the back face temperature [37].
Temperature overshoot from the exothermic reaction occurs
further out in the gas phase.
3.2. Thermal diffusivity
The thermal diffusivity represents the ability of a material to
conduct thermal energy relative to its ability to store thermal
energy and make the temperature uniform in the materials [38].
The thermal diffusivity value of the 4D C/C composite
decreased with the rise in temperature till 1173 K and later
on became fairly flat till 1523 K and onwards as shown in
Fig. 6. It may be noted that the thermal diffusivity of all the
constituents of C/C composites decreases with the rise in
temperature [16]. In this case, the thermal diffusivity decreased
by 44 mm2
/s when the temperature from room temperature
was increased to 1100 K which is almost the back-face
temperature of the specimens in arc heater testing. In C/C
composites, carbon fibers are the main channels of heat
transmission and hence their direction and distribution has a
major impact on thermal diffusivity. Their thermal diffusivity
varies from 60 to 19 mm2
/s in the temperature range of
500À1500 K. In all the specimens, the Z-axis fibers are along
the test direction and their volume percentage is 13.5, which
provides more continuous channels for the phonon transmis-
sion. After final densification with coal tar pitch, the residual
open porosity of the pre-densification step was further reduced
to 3.25% and the composite became more compact. These
entire factors contributed in higher thermal diffusivity at room
temperature. However, as the test temperature went up, the
phonon vibration frequency also increased resulting in scatter-
ing or decrease in the mean free path of the phonon leading to
a rapid decrease in thermal diffusivity. It also has an influence
on the decreasing trend of back-face temperature during
ablation testing.
3.3. Compression after ablation (CAA)
Fig. 7 shows the load–displacement curves of the specimen
1 and 6 after the ablation test. The linear region, representing
the true elastic response of the material was used to calculate
0 12 24 36 48 60
300
600
900
1200
Temperature(K)
Time (s)
Specimen 6
Specimen 1
Back-face absolute temperature
Distance from hot face = 15 mm
Fig. 5. Back-face temperature profile of sublimation (specimen 1) and
oxidation (specimen 6) regime ablation testing.
Fig. 6. Effect of temperature on thermal diffusivity and heat capacity of 4D C/C
composites along Z-axis.
0.0 0.2 0.4 0.6
0
7
14
21
28
Load(kN)
Dispalcement (mm)
Specimen 6Specimen 1
Fig. 7. Residual load–displacement curves of specimen 1 (sublimation regime)
and 6 (oxidation regime) after plasma arc heater testing.

the compressive modulus. The specimen 1 showed a residual
compressive strength of 75.63 MPa with a Young’s modulus
of 6.04 GPa. The specimen 6 showed a bilinear response in the
linear portion. The peak portion between 0.2 to 0.45 mm
displacements was the ultimate compressive load. The result-
ing strength and modulus were 69.15 MPa and 4.02 GPa,
respectively. These lower values were due to the deep
penetration of the oxidative plasma into the interfacial areas
of the composite. The load displacement curves represented a
typical brittle behavior without a catastrophic failure. The
specimen 1 failed on the non heat-effected side with both the
ends crushed and shear-failure in the central portion. The end
crushing is typical in this configuration of compression testing
and it is due to the buckling of carbon rods and matrix failure
(Fig. 8). When the load was applied on the specimen, shear
stress was induced along the interface between the specimen
end and the loading platen [39]. From the macro images
(Fig. 2) of the ablated specimens, a sequential difference in the
surface morphology can be observed. The surface of the
specimen 1 is smooth and flat with a few pinholes while deep
mesh like pits with surface undulation are visible on the whole
surface of the specimen 6. From the specimen 1 to 6, there is a
transition from smooth to rough surface. The material became
tougher at the heat-affected zone because of more gasification
and failed on the opposite side in the compression testing. The
specimen 6 sowed end brushing at the plasma heat-effected
zone. This behavior along with macro image (Fig. 2) con-
firmed the deep penetration of plasma into the intra rod spaces
with oxidation of matrix carbon. The 4D C/C composites show
extremely low interfacial strength between the fiber and the
matrix [40]. The strong oxidizing conditions and high-
temperature further reduced the strength and the carbon rods
failed due to macro-buckling.
4. Conclusions
4D C/C composite was fabricated using an intermediate
modulus carbon fiber and a hybrid processing method using a
TCVI and HiPIC processes resulting in a final density of
1.86 g/cm3
and a fiber volume fraction of 13.5% in Z-axis.
Plasma arc-heater testing was conducted to see the ablation
behavior. Arc-heater parameters like temperature, enthalpy,
velocity and flow rate were adjusted to create the ultra high-
temperature (4750 K) sublimation and high-temperature
(2467 K) oxidation regimes. The ablation rate increased with
the transition from oxygen-lean sublimation to oxygen-rich
oxidation environment. The back-face temperature showed a
similar but not so rapid rise in temperature as compared with
the large variation in the plasma stream temperatures at the hot
face. The endothermic sublimation reaction lowered the back-
face temperature while the exothermic oxidation reaction
reheated the specimen so that the net effect on the back-face
in both the cases was similar. In the compression test after
ablation, the ultra-high temperature exposed specimen showed
toughening at the plasma-affected zone, failed in end crushing
and shear mode from the opposite side while the high
temperature exposed specimen showed end brushing in plasma
heat affected zone with a lower residual strength and modulus.
References
[1] G. Savage, Carbon/Carbon Composites, Chapman Hall, London,
London, 1993, p. 173–174.
[2] L. Dagli, Y. Remond, Identification of the non-linear behavior a 4D
carbon–carbon material designed for aeronautic application, Appl.
Compos. Mater. 9 (2002) 1–15.
[3] D. Wang, Y. Zeng, X. Xiong, G.D. Li, Z.K. Chen, W. Sun, Y.L. Wang,
Preparation and ablation properties of ZrB2–SiC protective laminae for
carbon/carbon composites, Ceram. Int. 40 (2014) 14215–14222.
[4] X. Aubard, C. Cluzel, L. Guitard, P. Ladeveze, Modeling of the
mechanical behavior of 4D carbon/carbon composite materials, Compos.
Sci. Technol. 58 (5) (1998) 701–708.
[5] S. Farhan, K.Z. Li, L.J. Guo, A novel thermal gradient chemical vapor
infiltration process for carbon–carbon composites, New Carbon Mater. 22
(3) (2007) 247–252.
[6] G. Duffa, G.L. Vignoles, J.M. Goyhénèche, Y. Aspa, Ablation of C/C
composites: investigation of roughness set-up from heterogeneous reac-
tions, Int. J. Heat Mass Transfer 48 (2005) 3387–3401.
[7] S.M. Lee, International Encyclopedia of Composites, VCH Publishers,
New York, NY, 1990.
[8] D.R. Tenney, W.B. Lisagor, S.C. Dixon, Materials and structures for
hypersonic materials, NASA Tech. Memorandum 101501 (1988) 1–48.
[9] J.D. Guthrie, B. Battat, B.K. Severin. Thermal Protection Systems for
Space Vehicles, Advanced Materials Processing Technology, Rome, NY.
[10] S.R. Levine, E.J. Opila, M.C. Halbig, J.D. Kiser, M. Singh, J.A. Salem,
Evaluation of ultra-high temperature ceramics for aero propulsion use, J.
Eur. Ceram. Soc. 22 (14–15) (2002) 2757–2767.
[11] X. Aubard, C. Cluzel, L. Guitard, P. Ladeveze, Damage modeling of a
4D carbon/carbon composite for high temperature application, Ceram.
Int. 26 (6) (2000) 631–637.
[12] L. Delneste, B. Perez, An inelastic finite element model of 4D carbon–
carbon composites, AIAA J. 21 (1983) 1463–1475.
[13] P. Lamicq, Recent improvements in 4D carbon–carbon materials, AIAA
J. 77 (1977) 822–834.
[14] J. Lachaud, N. Bertrand, G.L. Vignoles, G. Bourget, F. Rebillat,
P. Weisbecker, A theoretical/experimental approach to the intrinsic
oxidation reactivities of C/C composites and of their components, Carbon
45 (14) (2007) 2768–2776.
[15] R.Z. Li, Y.D. Li, J.M. Su, H. Cui, Z.A. Su, S.J. Zhou, Study of the
properties of axial rod 4D woven C/C composite, Extended Abstracts,
Eurocarbon, 98, Science and Technology of Carbon, Strasbourg, France,
1998.
[16] J.C. Han, X.D. He, S.Y. Du, Oxidation and ablation of 3D carbon–carbon
composite at up to 3000 1C, Carbon 33 (4) (1995) 473–478.
10 mm
Fig. 8. Macro-morphologies of specimen 1 (left) and 2 (right) after compres-
sion after ablation test.

[17] J. Xie, K.Z. Li, H.J. Li, Q.G. Fu, L.J. Guo, Ablation behavior and
mechanism of C/C–ZrC–SiC composites under an oxyacetylene torch at
3000 1C, Ceram. Int. 39 (2013) 4171–4178.
[18] B. Chen, L.T. Zhang, L.F. Cheng, X.G. Luan, Erosion resistance of
needled carbon/carbon composites exposed to solid rocket motor plumes,
Carbon 47 (6) (2009) 1474–1479.
[19] Z.Q. Li, H.J. Li, S.Y. Zhang, K.Z. Li, Microstructure and ablation
behaviors of integer felt reinforced C/C–SiC–ZrC composites prepared by
a two-step method, Ceram. Int. 38 (2012) 3419–3425.
[20] Bonghwan Cho, Byung Yoon II, Microstructural interpretation of the
effect of various matrices on the ablation properties of carbon fiber
reinforced composites, Compos. Sci. Technol. 61 (2) (2001) 271–280.
[21] J. Yin, X. Xiong, H. Zhang, B. Huang, Microstructure and ablation
performances of dual-matrix carbon/carbon composites, Carbon 44 (3)
(2006) 1690–1694.
[22] B. Yan, Z.F. Chen, J.X. Zhu, J.Z. Zhang, Y. Jiang, Effects of ablation at
different regions in three-dimensional orthogonal C/SiC composites
ablated by oxyacetylene torch at 1800 1C, J. Mater. Process. Technol.
209 (2009) 3438–3443.
[23] S. Farhan, K.Z. Li, L.J. Guo, Q.M. Gao, F.T. Lan, Effect of density and
fiber orientation on the ablation behavior of carbon–carbon composites,
New Carbon Mater. 25 (3) (2010) 161–167.
[24] T. Ogasawara, T. Ishikawa, T. Yamada, R. Yokota, M. Itoh, Thermal
response and ablation characteristics of carbon fiber reinforced composite
with novel silicon containing polymer MSP, J. Compos. Mater. 36 (2002)
143–157.
[25] J. Yin, H. Zhang, X. Xiong, J. Zuo, H. Tao, Ablation properties of C/C-
SiC composites tested on an arc heater, Solid State Sci. 13 (11) (2011)
2055–2059.
[26] S. Farhan, N. Ul-Haq, W.S. Kuo, Degradation behavior of 4D carbon/
carbon composites under supersonic oxidative air plasma, Ceram. Int. 39
(6) (2013) 6019–7290.
[27] S. Farhan, R.M. Wang, K.Z. Li, Directional thermophysical, ablative and
compressive behavior of 3D carbon/carbon composites, Ceram. Int. 41
(8) (2015) 9763–9769.
[28] S. Farhan, K.Z. Li, L.J. Guo, Novel thermal gradient chemical vapor
infiltration process for carbon–carbon composites, New Carbon Mater. 22
(3) (2007) 247–252.
[29] S.F. Tang, J.Y. Deng, S.J. Wang, W.C. Liu, K. Yang, Ablation behavior
of ultra-high temperature ceramics composites, Mater. Sci. Eng. A 465
(1–2) (2007) 1–7.
[30] V.I. Trefilov, Ceramic and Carbon Matrix Composites, Chapman and
Hall, 1994, p. 360.
[31] F. Oriando, Understanding high recession rates of carbon ablators seen in
shear tests in an arc jet, in: 48th AIAA Aerospace Science Meeting, 2010.
[32] X.W. Luo, J.C. Robin, Y.S. Yu, Effect of temperature on graphite
oxidation behavior, Nucl. Eng. Des. 227 (2004) 273–280.
[33] H.S. Caram, N.R. Amundson, Diffusion and reaction in a stagnant
boundary layer about a carbon particle, Ind. Eng. Chem. Fundam. 16
(1977) 171–181.
[34] S.I. Savvatimskiy, Measurements of the melting point of graphite and the
properties of liquid carbon (A Review for 1963–2003), Carbon 43 (6)
(2005) 1115–1142.
[35] J.W. Metzger, M.J. Engel, N.S. Diaconis, Oxidation and sublimation of
graphite in simulated re-entry environments, AIAA J. 5 (1967) 451–460.
[36] A. Makino, T. Namikiri, K. Kimura, Combustion rates of graphite rods in
the forward stagnation field with high-temperature airflow, Combust.
Flame 132 (2003) 743–753.
[37] G.M. Song, et al., Ultra-high temperature ablation behavior of Ti2AlC
ceramics under an oxyacetylene flame, J. Eur. Ceram. Soc. 31 (2011)
855–862.
[38] Z. Tan, G.W. Guo, Thermophysical Properties of Engineering Alloys,
Metallurgy Industry Press, Beijing, 1994, p. 2–10.
[39] H. Hatta, K. Tanigguchi, Y. Kogo, Compressive strength of three-
dimensionally reinforced carbon/carbon composites, Carbon 43 (2)
(2005) 351–358.
[40] M.S. Aly-Hassan, H. Hatta, S. Wakayama, M. Watanabe, K. Miyagawa,
Comparison of 2D and 3D carbon/carbon composites with respect to
damage and fracture resistance, Carbon 41 (5) (2003) 1069–1078.

Sublimation CI SCI-2

Recomendados

Recomendados

Mais conteúdo relacionado

Mais procurados

Mais procurados (18)

Destaque

Destaque (19)

Semelhante a Sublimation CI SCI-2

Semelhante a Sublimation CI SCI-2 (20)

Mais de shameel farhan

Mais de shameel farhan (6)

Sublimation CI SCI-2