Interface is the key region which determines, to a great extent, the set of properties of all
heterogeneous systems, including composite materials. We reported interface healing of carbon fiber
reinforced thermoplastic composite material via resistive heating. The carbon fiber, T700 carbon fiber,
with a resistivity of 1.66·10-3 Ω·cm was used as the heating element while the matrix is polyarylether
sulfone with cardo. Micro-droplet experiment was used to study the interface strength before and after
heating to determine the healing efficiency. The measurement shows (experimental results show) that
resistive heating is an efficient way to heal cracks near interface.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3527

Cao, Z.

Fan, Y.

Hao, L.

Jiao, W.

Liu, W.

Wang, Q.

Wang, R.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 1, 01PCSI15 (3pp) (2013) 
 
 
2304-1862/2013/2(1)01PCSI15(3) 01PCSI15-1  2013 Sumy State University 
Healing Carbon Fiber/Polymer Composites by Resistive Heating 
 
R. Wang1,*, Z. Cao1, L. Hao1, Q. Wang1, W. Liu2, W. Jiao1, Y. Fan1 
 
1 Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin, China 
2 School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China 
 
(Received 08 June 2013; published online 02 September 2013) 
 
Interface is the key region which determines, to a great extent, the set of properties of all 
heterogeneous systems, including composite materials. We reported interface healing of carbon fiber 
reinforced thermoplastic composite material via resistive heating. The carbon fiber, T700 carbon fiber, 
with a resistivity of 1.66·10-3 Ω·cm was used as the heating element while the matrix is polyarylether 
sulfone with cardo. Micro-droplet experiment was used to study the interface strength before and after 
heating to determine the healing efficiency. The measurement shows (experimental results show) that 
resistive heating is an efficient way to heal cracks near interface. 
 
Keywords: Interface Healing, Resistive Heating, Thermoplastic, Carbon Fiber. 
 
  PACS numbers: 61.46.Fg 
 
 
                                                          
* wrg@hit.edu.cn 
1. INTRODUCTION 
 
Composite materials always suffer from delaminat-
ing caused by long term usage or external impact. 
However, damages are difficult to detect since most of 
them are buried deeply within the structures. Once 
damages developed, the integrity of the structure 
would be greatly compromised. Therefore, it is desira-
ble to repair the composites to elongate the lifetimes 
and to lower the maintenance cost.  
Healing composites can be carried out by several 
methods. Dry [1] and White [2] used microcapsules 
filled with healing agents to heal microcracks. Kausch 
and co-workers [3] showed that single cracks in PMMA 
could be healed by rejoining and welding above the 
glass transition temperature. Kwon et al [4, 5] reported 
an electrical resistive heating method via carbon fiber 
network. Park et al [6-18] reported electrical resistive 
heating to heal a thermally mendable polymer.  
In this paper, we studied the healing efficiency of 
resistive heating induced interface healing by micro-
droplet experiments. A polyarylether sulfone with car-
do (PESC) microdroplet is repeatedly pulled of and re-
healed, and the interface shear stress is measured for 
the rehealed microdoplets. 
 
2. EXPERIMENTS 
 
2.1 Materials 
 
Commercially available carbon fiber T700SC-12000-
50C (Toray, Japan) with a diameter of about 7µm, was 
used. A thermoplastic resin, polyarylether sulfone with 
cardo (PESC) was provided by Wuxi Resin Factory 
(China). The N-Methyl pyrrolidone(NMP) and acetone 
were provided by J&K Chemical Ltd.  
 
2.2 Preparation of micro-droplet specimens  
 
We first detached a single filament of carbon fiber 
from the fabric and then fastened it to a thin paper 
holder (20 × 70 mm) with double sided adhesive tape. 
The free fiber length was approximately 30mm. The 
micro-droplet specimen was made by applying PESC 
resin/ NMP at a weight ratio of 20:80 .Then the speci-
men was adhered on a single filament with an embed-
ded length of 40–80µm using a fine-point applicator 
(Fig.1). Then the specimens were cured in an air dry 
oven (101A-1, Shanghai Laboratory Instrument Works 
Co., Ltd.) under the normal pressure at 350℃ for 3 h.  
 
 
 
Fig. 1 -  Schematic drawing of micro-droplet composite 
specimens 
 
2.3 Mechanical tests 
 
Interfacial shear strength was measured by the mi-
cro-droplet test to determine the interfacial adhesion 
ability of fibers and matrix. Specimens were tested at 
room temperature on the interfacial strength machine 
(Tohei Sanyon Corporation of Japan) at a cross-head 
speed of 0.5µm/min. Two knives were brought very 
close to each other, as shown in Fig. 2, and eventually 
came in contact with the solid resin droplet. The fiber 
was pulled by an actuator while the force required to 
de-bond the droplet from the fiber was recorded. The 
force to pull the fiber out of the epoxy composite is 
measured and used to calculate the interfacial shear 
strength τ, which is expressed as 
 
dl
Fmax  (2.1) 
 
where Fmax is the peak pullout force, d is the di-
ameter of carbon fiber, and l is the embedded length of 
a micro-droplet.  
 R. WANG, Z. CAO, L. HAO, ET AL. PROC. NAP 2, 01PCSI15 (2013) 
 
 
01PCSI15-2 
 
 
Fig. 2 -  The process of micro-droplet test 
 
The SEM images of the debonded microdroplet are 
shown in Fig. 3. It is found that the surface of the drop-
let gets rough and some microcracks appears, indicat-
ing plastic deformations during the pulling process. A 
meniscus shaped resin was left on the fiber showing 
the breaking position. 
 
 
 
Fig. 3 - SEM images of the debonded microdroplet 
 
2.4 Healing experiment 
 
After pulling off the resin micro-droplet, electrical 
current was applied to the specimen to heal the inter-
face. After healing, the specimen was cooled down to 
room temperature and the whole process is monitored 
by an optical micrograph. Fig. 4 shows a healed micro-
droplet, and by zooming in, it is found that the resin 
attaches to the carbon fiber again. However, the surface 
of the droplet is not as smooth as the original one and 
the contact angle becomes larger.  
 
 
 
Fig. 4 - SEM images of the debonded microdroplet after 
resistive heating 
 
To determine the healing efficiency accurately, 
pulling off and resistive heating was repeatedly applied 
to a single microdroplet, and the interface adhesion 
was recorded for each cycle. SEM study shows that 
after each heating cycle, the microdroplet tends to vary 
its shape and dimensions a little bit, while the 
interface resumes attachment. This corresponds to 
some mass loss for each pulling off – resistive heating 
cycles, since after each cycle there will be a meniscus 
left on the carbon fibers. This mass loss applied a 
limitation on the heating times in the case of 
microdroplet test, however for the case of bulk carbon 
fiber reinforced composites, this is not an issue, since 
the lost mass will always be recovered for next heating 
cycle. 
 
3. RESULTS AND DISCUSSIONS 
 
The shape of the microdroplet varies after resistive 
heating, as well as the interface structures. This indi-
cates a potential change of the interface shear strength. 
So we studied the healing efficiency as a function of the 
heating electrical current and the heating times. 
The healing efficiency was defined to be the strain 
energy ratio of healed sample and virgin sample up to 
the maximum strength of the virgin sample. 
 
 
 
Fig. 5 - Healing efficiency dependence of electrical current 
 
Fig.5 shows healing efficiency as a function of the 
electrical current. For an electrical current smaller than 
5mA, the interface can not be healed, indicating that the 
temperature is lower than the glass transition tempera-
ture of PESC. As the current increased to 7mA, healing 
takes place and the interracial shear strength recovers.  
 
first second third fourth fifth
0
20
40
60
80
 
 
H
e
a
li
n
g
 e
ff
ic
ie
n
c
y
 (
%
)
Healing times
 
 
Fig. 6 - Healing efficiency as a function of healing times. 
 
However, increasing the current further tends to 
cause the healing efficiency to decline. This can be at-
tributed to the thermal decomposition of the matrix 
material due to the extra energy input. This indicates 
 HEALING CARBON FIBER/POLYMER COMPOSITES BY … PROC. NAP 2, 01PCSI15 (2013) 
 
 
01PCSI15-3 
that controlling the heating current is critical for heal-
ing carbon fiber reinforced composite materials, since 
the heating tends to result in multi-effect. 
The effect of healing on actual interfacial bonding 
behavior was evaluated using micro-droplet tests. After 
the resistive heating process, the microdroplet recov-
ered its interfacial shear strength. Fig.6 shows the 
healing efficiency of the same specimen as a function of 
the healing times with an electrical current of 7 mA. 
The healing efficiency ranges from 91.1 % to 87.9 %, 
and shows little degradation after multi healing cycle. 
From the high healing efficiency of the specimens, mul-
tiple healing of PESC composites with carbon fibers 
using electrical resistive heating was confirmed. 
4. CONCLUSIONS 
 
Interface damages in carbon fiber reinforced ther-
moplastic composite were healed using resistive heat-
ing. Micro-droplet tests were used to discern the possi-
bility of healing from the healed specimen showed high 
interfacial shear strength. The best healing current 
was found to be around 7mA. The healing times has 
little effect to the healing efficiency, the maximum and 
minimize of healing efficiency are 91.1% and 87.9%. 
The self-healing ability of the carbon fiber/PESC com-
posite was confirmed by electrical resistive heating. 
 
 
 
REFERENCES 
 
1. C. Dry, Compos. Struct. 35(3), 263 (1996). 
2. S.R. White, N.R. Sottos, P.H. Geubelle, J.S. Moore, 
M.R. Kessler, S.R. Sriram et al., Nature. 415, 817 (2002). 
3. R.P. Wool, Soft Matter. 4(3), 400 (2008). 
4. N. Kwok, H.T. Hahn, J. Compos. Mater. 41(13), 1635 
(2007). 
5. J.S. Park, K. Takahashi, Z.H. Guo, Y. Wang, E. Bolanos, 
C. Hamann-Schaffner et al., Compos. Mater. 42(26), 2869 
(2008). 
6. J.S. Park, T Darlington, A.F. Starr, K. Takahashi, 
J. Riendeau, H.T. Hahn, Compos. Sci. Technol. 70(15) 
2154 (2010). 
7. J.S. Park, H.S. Kim, H.T. Hahn, Compos. Sci. Technol. 
69(7-8), 1082 (2009). 
8. C. Dry, Compos Struct. 35(3), 263. 1996. 
9. S.R. White, N.R. Sottos, P.H. Geubelle, J.S. Moore, 
M.R. Kessler, S.R. Sriram, et al., Nature. 409, 794 2001. 
10. X. Chen, M.A. Dam, K. Ono, A. Mal, H.B. Shen, S.R. Nutt, 
et al., Science. 295, 1698 (2002) 
11. X. Chen, F. Wudl, A. Mal, H. Shen, S.R. Nutt, Macro-
molecules, 36, 1802. (2003) 
12. S.D. Bergman, F. Wudl, J. Mater. Chem. 18, 41. (2008) 
13. Y. Wang, E. Bolanos, J.S. Park, F. Wudl, H.T. Hahn. 
SPIE: Smart Structures and NDE Conference Proceed-
ings, San Diego, California, USA. 6526, 65261 (2007) 
14. N. Kwok, H.T. Hahn, J. Compos. Mater. 41, 1635 (2007) 
15. J.S. Park, K. Takahashi, Z. Guo, Y. Wang, E. Bolanos, 
C. Hamann-Schaffner, et al., J Compos Mater; 42(26), 
2869 (2008) 
16. M.R. Kessler, S.R. White, J. Polym. Sci. Part A. 40, 2373 
(2002) 
17. G. Sun, H. Sun, Y. Liu, B. Zhao, N. Zhu, K. Hu, Polymer. 
48, 330 (2007). 
18. A. Todoroki, Y. Tanaka, Y. Shimamura, Compos. Sci. 
Technol. 62, 1151 (2002). 
 
 


English

Healing Carbon Fiber/Polymer Composites by Resistive Heating

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 1, 01PCSI15 (3pp) (2013)   2304-1862/2013/2(1)01PCSI15(3) 01PCSI15-1  2013 Sumy State University Healing Carbon Fiber/Polymer Composites by Resistive Heating  R. Wang1,*, Z. Cao1, L. Hao1, Q. Wang1, W. Liu2, W. Jiao1, Y. Fan1  1 Center for Composite Materials and Structures, Harbin Institute of Technology, Harbin, China 2 School of Materials Science and Engineering, Harbin Institute of Technology, Harbin, 150001, China  (Received 08 June 2013; published online 02 September 2013)  Interface is the key region which determines, to a great extent, the set of properties of all heterogeneous systems, including composite materials. We reported interface healing of carbon fiber reinforced thermoplastic composite material via resistive heating. The carbon fiber, T700 carbon fiber, with a resistivity of 1.66·10-3 Ω·cm was used as the heating element while the matrix is polyarylether sulfone with cardo. Micro-droplet experiment was used to study the interface strength before and after heating to determine the healing efficiency. The measurement shows (experimental results show) that resistive heating is an efficient way to heal cracks near interface.  Keywords: Interface Healing, Resistive Heating, Thermoplastic, Carbon Fiber.    PACS numbers: 61.46.Fg                                                             * wrg@hit.edu.cn 1. INTRODUCTION  Composite materials always suffer from delaminat-ing caused by long term usage or external impact. However, damages are difficult to detect since most of them are buried deeply within the structures. Once damages developed, the integrity of the structure would be greatly compromised. Therefore, it is desira-ble to repair the composites to elongate the lifetimes and to lower the maintenance cost.  Healing composites can be carried out by several methods. Dry [1] and White [2] used microcapsules filled with healing agents to heal microcracks. Kausch and co-workers [3] showed that single cracks in PMMA could be healed by rejoining and welding above the glass transition temperature. Kwon et al [4, 5] reported an electrical resistive heating method via carbon fiber network. Park et al [6-18] reported electrical resistive heating to heal a thermally mendable polymer.  In this paper, we studied the healing efficiency of resistive heating induced interface healing by micro-droplet experiments. A polyarylether sulfone with car-do (PESC) microdroplet is repeatedly pulled of and re-healed, and the interface shear stress is measured for the rehealed microdoplets.  2. EXPERIMENTS  2.1 Materials  Commercially available carbon fiber T700SC-12000-50C (Toray, Japan) with a diameter of about 7µm, was used. A thermoplastic resin, polyarylether sulfone with cardo (PESC) was provided by Wuxi Resin Factory (China). The N-Methyl pyrrolidone(NMP) and acetone were provided by J&K Chemical Ltd.   2.2 Preparation of micro-droplet specimens   We first detached a single filament of carbon fiber from the fabric and then fastened it to a thin paper holder (20 × 70 mm) with double sided adhesive tape. The free fiber length was approximately 30mm. The micro-droplet specimen was made by applying PESC resin/ NMP at a weight ratio of 20:80 .Then the speci-men was adhered on a single filament with an embed-ded length of 40–80µm using a fine-point applicator (Fig.1). Then the specimens were cured in an air dry oven (101A-1, Shanghai Laboratory Instrument Works Co., Ltd.) under the normal pressure at 350℃ for 3 h.     Fig. 1 -  Schematic drawing of micro-droplet composite specimens  2.3 Mechanical tests  Interfacial shear strength was measured by the mi-cro-droplet test to determine the interfacial adhesion ability of fibers and matrix. Specimens were tested at room temperature on the interfacial strength machine (Tohei Sanyon Corporation of Japan) at a cross-head speed of 0.5µm/min. Two knives were brought very close to each other, as shown in Fig. 2, and eventually came in contact with the solid resin droplet. The fiber was pulled by an actuator while the force required to de-bond the droplet from the fiber was recorded. The force to pull the fiber out of the epoxy composite is measured and used to calculate the interfacial shear strength τ, which is expressed as  dlFmax  (2.1)  where Fmax is the peak pullout force, d is the di-ameter of carbon fiber, and l is the embedded length of a micro-droplet.   R. WANG, Z. CAO, L. HAO, ET AL. PROC. NAP 2, 01PCSI15 (2013)   01PCSI15-2   Fig. 2 -  The process of micro-droplet test  The SEM images of the debonded microdroplet are shown in Fig. 3. It is found that the surface of the drop-let gets rough and some microcracks appears, indicat-ing plastic deformations during the pulling process. A meniscus shaped resin was left on the fiber showing the breaking position.    Fig. 3 - SEM images of the debonded microdroplet  2.4 Healing experiment  After pulling off the resin micro-droplet, electrical current was applied to the specimen to heal the inter-face. After healing, the specimen was cooled down to room temperature and the whole process is monitored by an optical micrograph. Fig. 4 shows a healed micro-droplet, and by zooming in, it is found that the resin attaches to the carbon fiber again. However, the surface of the droplet is not as smooth as the original one and the contact angle becomes larger.     Fig. 4 - SEM images of the debonded microdroplet after resistive heating  To determine the healing efficiency accurately, pulling off and resistive heating was repeatedly applied to a single microdroplet, and the interface adhesion was recorded for each cycle. SEM study shows that after each heating cycle, the microdroplet tends to vary its shape and dimensions a little bit, while the interface resumes attachment. This corresponds to some mass loss for each pulling off – resistive heating cycles, since after each cycle there will be a meniscus left on the carbon fibers. This mass loss applied a limitation on the heating times in the case of microdroplet test, however for the case of bulk carbon fiber reinforced composites, this is not an issue, since the lost mass will always be recovered for next heating cycle.  3. RESULTS AND DISCUSSIONS  The shape of the microdroplet varies after resistive heating, as well as the interface structures. This indi-cates a potential change of the interface shear strength. So we studied the healing efficiency as a function of the heating electrical current and the heating times. The healing efficiency was defined to be the strain energy ratio of healed sample and virgin sample up to the maximum strength of the virgin sample.    Fig. 5 - Healing efficiency dependence of electrical current  Fig.5 shows healing efficiency as a function of the electrical current. For an electrical current smaller than 5mA, the interface can not be healed, indicating that the temperature is lower than the glass transition tempera-ture of PESC. As the current increased to 7mA, healing takes place and the interracial shear strength recovers.   first second third fourth fifth020406080  Healing efficiency (%)Healing times  Fig. 6 - Healing efficiency as a function of healing times.  However, increasing the current further tends to cause the healing efficiency to decline. This can be at-tributed to the thermal decomposition of the matrix material due to the extra energy input. This indicates  HEALING CARBON FIBER/POLYMER COMPOSITES BY … PROC. NAP 2, 01PCSI15 (2013)   01PCSI15-3 that controlling the heating current is critical for heal-ing carbon fiber reinforced composite materials, since the heating tends to result in multi-effect. The effect of healing on actual interfacial bonding behavior was evaluated using micro-droplet tests. After the resistive heating process, the microdroplet recov-ered its interfacial shear strength. Fig.6 shows the healing efficiency of the same specimen as a function of the healing times with an electrical current of 7 mA. The healing efficiency ranges from 91.1 % to 87.9 %, and shows little degradation after multi healing cycle. From the high healing efficiency of the specimens, mul-tiple healing of PESC composites with carbon fibers using electrical resistive heating was confirmed. 4. CONCLUSIONS  Interface damages in carbon fiber reinforced ther-moplastic composite were healed using resistive heat-ing. Micro-droplet tests were used to discern the possi-bility of healing from the healed specimen showed high interfacial shear strength. The best healing current was found to be around 7mA. The healing times has little effect to the healing efficiency, the maximum and minimize of healing efficiency are 91.1% and 87.9%. The self-healing ability of the carbon fiber/PESC com-posite was confirmed by electrical resistive heating.    REFERENCES  1. C. Dry, Compos. Struct. 35(3), 263 (1996). 2. S.R. White, N.R. Sottos, P.H. Geubelle, J.S. Moore, M.R. Kessler, S.R. Sriram et al., Nature. 415, 817 (2002). 3. R.P. Wool, Soft Matter. 4(3), 400 (2008). 4. N. Kwok, H.T. Hahn, J. Compos. Mater. 41(13), 1635 (2007). 5. J.S. Park, K. Takahashi, Z.H. Guo, Y. Wang, E. Bolanos, C. Hamann-Schaffner et al., Compos. Mater. 42(26), 2869 (2008). 6. J.S. Park, T Darlington, A.F. Starr, K. Takahashi, J. Riendeau, H.T. Hahn, Compos. Sci. Technol. 70(15) 2154 (2010). 7. J.S. Park, H.S. Kim, H.T. Hahn, Compos. Sci. Technol. 69(7-8), 1082 (2009). 8. C. Dry, Compos Struct. 35(3), 263. 1996. 9. S.R. White, N.R. Sottos, P.H. Geubelle, J.S. Moore, M.R. Kessler, S.R. Sriram, et al., Nature. 409, 794 2001. 10. X. Chen, M.A. Dam, K. Ono, A. Mal, H.B. Shen, S.R. Nutt, et al., Science. 295, 1698 (2002) 11. X. Chen, F. Wudl, A. Mal, H. Shen, S.R. Nutt, Macro-molecules, 36, 1802. (2003) 12. S.D. Bergman, F. Wudl, J. Mater. Chem. 18, 41. (2008) 13. Y. Wang, E. Bolanos, J.S. Park, F. Wudl, H.T. Hahn. SPIE: Smart Structures and NDE Conference Proceed-ings, San Diego, California, USA. 6526, 65261 (2007) 14. N. Kwok, H.T. Hahn, J. Compos. Mater. 41, 1635 (2007) 15. J.S. Park, K. Takahashi, Z. Guo, Y. Wang, E. Bolanos, C. Hamann-Schaffner, et al., J Compos Mater; 42(26), 2869 (2008) 16. M.R. Kessler, S.R. White, J. Polym. Sci. Part A. 40, 2373 (2002) 17. G. Sun, H. Sun, Y. Liu, B. Zhao, N. Zhu, K. Hu, Polymer. 48, 330 (2007). 18. A. Todoroki, Y. Tanaka, Y. Shimamura, Compos. Sci. Technol. 62, 1151 (2002).   

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Healing Carbon Fiber/Polymer Composites by Resistive Heating

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