Analysis of Interfacial Adhesion Behaviors bySingle-Fiber Composite Tensile Tests and SurfaceWettability Tests

Lili Sun,1,2 Yuxi Jia,1 Fengde Ma,1 Sheng Sun,1 Jiang Zhao,3 Charles C. Han3

1School of Materials Science and Engineering, Shandong University, Jinan, China

2Editorial Department of University Journal, Qingdao University of Science and Technology, Qingdao, China

3Beijing National Laboratory of Molecular Science, Joint Laboratory of Polymer Science and Materials,Institute of Chemistry, Chinese Academy of Sciences, Beijing, China

The interfacial adhesion and the mechanical propertiesof glass fiber reinforced epoxy matrix composite werestudied systematically by changing the ratio of the cur-ing agent to epoxy and also the surface treatment offibers. A strong correlation between the interfacialshear strength and the work of adhesion was found,i.e., the interfacial shear strength is scaled linearlywith the interfacial work of adhesion. An empirical for-mula has been proposed for the relation between theinterfacial shear strength and the work of adhesion,from which the equilibrium interatomic distance atthe interface between matrix and fiber was evalua-ted. POLYM. COMPOS., 31:1457–1464, 2010. ª 2009 Societyof Plastics Engineers

INTRODUCTION

It is widely acknowledged that the fiber/matrix inter-

face influences the properties of fiber-reinforced polymer

matrix composites, including the stress transfer efficiency

from matrix to fibers, the stress build-up in the broken

fibers, fracture developing process, and so on. Consider-

able research attentions have been paid on the improve-

ment of the adhesion at the interface by ways to change

the interfacial properties [1–7], and both experimental

investigations and theoretical studies including simula-

tions have been made to address this question [8–11].

However, the precondition of tailoring the composites to

achieve the desired performance is to measure and evalu-

ate the interfacial properties accurately. So, the character-

istics of the fiber/matrix interface were widely investi-

gated during recent years [12–19].

Interfacial shear strength (IFSS) is a simple but impor-

tant mechanical parameter to characterize the adhesion

strength between fiber and matrix. Multiple methods have

been adopted to determine this parameter, such as single-

fiber composite fragmentation [12–14], single fiber

pulled-out [15, 16], and microbond [17–19] method.

Although there are arguments about the accuracy of inter-

facial shear strength, the fragmentation method has been

very popular and feasible.

Besides, the thermodynamic parameter which is called

‘work of adhesion (Wa)’ is another parameter to character-

ize the interfacial adhesion. It has long been believed that

the interfacial shear strength correlates with the work of

adhesion (Wa) [20–22]. This correlation has been contro-

versial quantitatively. By examining a number of thermo-

plastic matrices and glass fibers (uncoated or coated with

various sizing agents), Pisanova and Mader reported a lin-

ear relationship between Wa and IFSS [3]. Bismarck et al.

investigated the modified carbon fibers in polyamide ma-

trix [23–25] and found a nonlinear correlation between

Wa and IFSS [24]. There are also reports showing no cor-

relation between these two parameters, such as the work

of Park et al [26]. By studying the electro-deposition

(ED)-treated carbon fiber/epoxy-polyetherimide (PEI)

composite, they believed that the predominant contribu-

tion to IFSS comes from the matrix toughness.

Such a controversy made us to revisit this issue, and in

this work, we systematically vary the interfacial adhesion

between glass fiber and epoxy matrix and try to establish

a quantitative relationship between the work of adhesion

and IFSS. In our experiments, the fiber-epoxy adhesion

Correspondence to: Y. Jia; e-mail: jia_yuxi@sdu.edu.cn or J. Zhao; e-mail:

jzhao@iccas.ac.cn

Contract grant sponsor: National Basic Research Program of China;

contract grant numbers: 2003CB615600, 2010CB631102.

DOI 10.1002/pc.20932

Published online in Wiley InterScience (www.interscience.wiley.com).

VVC 2009 Society of Plastics Engineers

POLYMER COMPOSITES—-2010

was tuned by growing inert self-assembled monolayer of

alkanesilane and further oxidation to the monolayer. The

work of adhesion and interfacial shear strength data were

measured by wettability measurement and single fiber

fragmentation measurement, respectively.

EXPERIMENTAL

Materials

The composite under investigation was glass fiber-ep-

oxy system. Glass fibers with a diameter of 36 lm (Bei-

jing Glass Fiber Co., China) were used as a model rein-

forcing material. To tune the interfacial properties

between the fiber and epoxy matrix, octadecyltrichlorosi-

lane (OTS) was adopted to form self-assembled mono-

layers (SAMs) on glass fiber surface. The chemical com-

ponent of the polymer matrix was diglycidyl ether of

bisphenol-F (DGEBF), (Epoxy 830 from Wuxi DIC Ep-

oxy Co., China) and polypropylenediamine D230

(Huntsman Co.).

Methods

Testing of Physical Properties of the Glass Fiber. Ten-

sile modulus of the glass fiber was tested by single-fiber

tensile test, which was carried out by separating the fibers

from the bundle and mounting them on a paper frame

[27]. The fracture elongation of glass fiber was defined as

the strain applied to the single-fiber composite when the

first fiber break appears, which is bigger than the value

obtained by single-fiber tensile test because of the protec-

tion of matrix. Weibull shape parameters were tested by

single-fiber composite tensile test [28]. The parameters

obtained from single-fiber composite tensile test can

reflect the real fracture process of the glass fiber in ma-

trix. Mechanical properties and Weibull distribution pa-

rameters of the glass fiber are listed in Table 1.

Surface Treatment of Glass Fibers. The self-

assembled monolayers of OTS were prepared according

to protocols reported in Ref. 29. To grow self-assembled

monolayers of silane on glass fibers, the fibers were firstly

cleaned by ultrasonication in both acetone and distilled

water thoroughly. Afterward, they were immersed in pira-

nha solution (a mixture of sulfate acid and hydroxyl per-

oxide at a volume ratio of 3:7) at 1108C for 100 min.

(Caution: Piranha solution is extremely corrosive and spe-

cial caution should be taken when handling it.). After

being rinsed thoroughly with deionized water, the fibers

were blown dry under nitrogen flow and used immedi-

ately. Such a treatment makes the glass fiber’s surface

rich of hydroxyl groups (Fig. 1).

Afterward, the glass fibers were immersed in OTS

solution in cyclohexane (1:500 by volume) for 30 min

(Fig. 1). After being removed from the solution, the fibers

were intensively rinsed in a number of solvent to remove

possible physical adsorption. The fiber surface coated

with a layer of dense long alkyl chains with methyl

(��CH3) as terminal group was proved to be hydrophobic.

To tune the surface polarity, the hydrophobically modi-

fied fibers were oxidized by ozone initiated by ultraviolet

for different amount of time [30]. The ozone oxidized the

monolayer coating on the surface, resulted in the fact that

the methyl groups (��CH3) were oxidized to carboxyl

groups (��COOH) or the long alkyl chains degraded

(Fig. 1). It is worth pointing out that the fibers should be

used for composite preparation immediately after the

ozone treatment, as the self-assembled monolayer will go

on degrading during storage.

Tensile Test of Single-Fiber Composites. Dog bone-

shaped tensile specimens were prepared by a home-built

fiber positioning apparatus described elsewhere [31]. In

each specimen, two fibers separated far away from each

other were embedded. The interfiber spacing is over 10

times of the fiber diameter, regarded that no interfiber

interactions exist [13, 14, 31]. Tensile measurement was

conducted on a tensile test instrument equipped with an

optical microscope so that the fiber failure could be moni-

tored simultaneously during the stress–strain testing.

Details were described in a previous publication [31]. The

interfacial shear strength, s, is calculated using the Kelly-

Tyson equation [12]:

s ¼ Krf ðlcÞ2lc

df ð1Þ

where rf(lc), df, lc denote fiber tensile strength at the critical

fragment length, the fiber diameter, and the mean critical

fragment length, respectively. Usually, K adopts a mean

value of 3/4. The fiber tensile strength, rf(lc), at the fiber crit-ical length is calculated from the following equation [32]:

rfðlcÞ ¼ r0 l0=lcð Þ1=q ð2Þwhere r0 denotes the fiber strength at the gauge-length l0,and q the Weibull shape parameter, describing the statisti-

cal spread in strength, which is tested by single-fiber com-

posite tensile test [28].

Measurement of Wettability. The sessile drop method

is conducted to obtain the surface energy of solid matrix

by a home-made goniometer. Two test liquids, water

(cd ¼ 21.8 mN�m21 and cp ¼ 51.0 mN�m21, where

cd and cp are the dispersive and polar surface tension,

respectively), and ethylene glycol (cd ¼ 30.1 mN�m21, cp

¼ 17.6 mN�m21) were used for measurements at 208C 618C. Contact angle measurements were performed within

5 s after droplet application to minimize the effect of

evaporation.

The thermodynamic work of adhesion, Wa, was esti-

mated according to Young-Dupre equation, Wa ¼ cL(1 þ

1458 POLYMER COMPOSITES—-2010 DOI 10.1002/pc

cos h), where cL denotes the surface tension of the wet-

ting liquid, and h the measured contact angle of the wet-

ting liquid on solid substrate surface.

Single fiber contact angle test was adopted to estimate

Wa between polymer and fiber. The fiber was immersed

in the freshly prepared mixture of epoxy and curing agent,

and removed afterward. Tiny droplets of epoxy were

observed on the fiber. Then, the fiber sample was sus-

pended horizontally and cured with the same curing steps

as SFC. For the determination of Wa, the surface tension

of the solid polymer (cS) was adopted instead of cL when

using Young-Dupre equation, because solid epoxy poly-

mer serves as the wetting substance, which was originally

liquid on the fiber’s surface [1]. The contact angle h is

determined by measuring the contour of the solidified

polymer droplet on fibers [33]. The images of the micro-

droplets were captured by an optical microscope and the

droplet contour analysis was conducted using DSA1 Drop

Analysis Software (Co. KruSS, Germany).

RESULTS AND DISCUSSION

Mechanical Properties of Matrices at VaryingCuring Agent Ratio

As a characterization of the epoxy matrix, the mechan-

ical properties of the epoxy matrix are measured and plot-

ted against the ratio of curing agent to epoxy (Fig. 2a–c,

this ratio is denoted as R in the text, and R ranges from

24:100 to 48:100). It can be seen that the initial elastic

modulus did not vary with R varying from 24:100 to

48:100 (w/w), but the yield strength and fracture strength

showed the maximum value at the stoichiometric ratio of

curing agent (34:100 (w/w)). As we know, the maximum

cross-linking density is approached at the stoichiometric

ratio and the small freedom molecules exist at the non-

stoichiometric ratio of curing agent, including low (epoxy

is surplus) and high (curing agent is surplus) curing agent

ratio. The nondependence of initial elastic modulus on

curing agent ratio was understood because the experiment

temperature was far away below the glass transition tem-

perature, the polymer chain motion was restricted [34],

especially at the initial elastic deformation stage. How-

ever, the small freedom molecules began to move when

the matrix got into plastic deformation stage, and the dif-

ferent cross-linking density introduced by varying curing

agent ratio worked. Consequently, both the yield strength

and fracture strength decreased when the curing agent ra-

tio departed from the stoichiometric ratio.

Properties of Fiber Composite at VaryingCuring Agent Ratio

A careful measurement of properties of single-fiber

composite at different ratio of curing agent to epoxy was

TABLE 1. Mechanical properties and Weibull distribution parameters of the glass fiber.

Parameters Tensile strength (MPa) Tensile modulus (GPa) Elongation (%) Weibull shape parameter

Uncoated fiber 838 6 67 46.8 6 3.7 1.79 6 0.2 5.51

Coated fiber 878 6 83 44.5 6 3.4 1.81 6 0.2 7.75

FIG. 1. Schematic representation for fiber surface treatment.

DOI 10.1002/pc POLYMER COMPOSITES—-2010 1459

conducted (R ranges from 24:100 to 48:100). Such meas-

urements were performed because the adhesion between

the matrix and the fiber may vary as R changes, which is

attributed to the fact that the curing agent and the epoxy

interact with the fiber surface selectively at the stage of

liquid mixture of epoxy and curing agent wetting the

fiber.

Micro-Failure Modes. The typical micrographs for

microfailure modes with changing ratio R are shown in

Fig. 3a–e. When R was changed from 24:100 to 34:100,

the microfailure modes at the interface experienced an

evolution from complete failure to partial failure and to

nonfailure (when R equals 34:100). Beyond this value, the

failure mode changed to partial, complete failure again, as

the ratio value increase. From polarized micrograph dis-

played in the middle column of Fig. 3a–e, a change of

the pattern in the interfacial stress was discovered: it is

more dispersive or spreading at low curing agent ratio Rwhile this becomes more and more concentrated at the

interface when this ratio got closer to the optimum value

(the stoichiometric ratio). An opposite trend was found at

further increasing the ratio. The interface nonfailure mode

appeared around stoichiometric ratio of 32:100–38:100

(w/w) (Fig. 3c). The interfacial adhesion strength repre-

sented by interface failure mode is consistent with matrix

mechanical properties, as discussed in ‘‘Mechanical Prop-

erties of Matrices at Varying Curing Agent Ratio.’’

Additionally, the observation of the interfacial stress is

in good agreement with our simulation results published

previously [11], which showed that, for strong interfacial

adhesion, it exhibits interface nonfailure mode and the

stress concentrated at the interface and also around crack

tip. This is true for both small (Illustration 4e in Ref. 11.)

and large crack (Illustration 5e in Ref. 11, large crack

means the fiber break with penetration into the matrix.).

For the case of weak interface (weak interfacial adhesion)

exhibiting interface failure mode, there is no stress con-

centration at the interface near the fiber breakpoint due to

interface failure, and only vague concentration region was

found at the termination of interface failure (Illustration

7e in Ref. 11.).

IFSS and Wettability. The data of IFSS at different

curing agent ratio are plotted in Fig. 4a, in which a maxi-

mum value of IFSS was found at the ratio value of

34:100 (w/w), on a similar trend with that of yield

strength and fracture strength. This is an interesting find-

ing, showing the cross-scale correlation between the

micro- and macromechanical properties. Besides, the

microfailure modes discussed earlier are consistent with

the obtained mechanical properties.

The data of contact angle of epoxy on fiber surface at

different ratio of curing agent are shown in Fig. 4b, in

which an inverse trend to that of IFSS is found. The posi-

tion of the maximum value of IFSS agrees with that of

the minimum value of the contact angle. However, it is

difficult to define the relationship between IFSS and wett-

ability from these data, because there are variations in the

mechanical properties of matrix with varying curing agent

ratio which have effects on IFSS as well. So, properties

of fiber composite at different fiber surface treatment,

including wettability and IFSS, were investigated in

‘‘Properties of Fiber Composite at Different Fiber Surface

Treatment.’’

Additionally, it has been concerned that the contact

angle measurement with solidified polymers may not be

accurate to show the interfacial adhesion property [1].

However, we believe that our data are not in this case.

This is demonstrated by the results of the epoxy contact

angle before and after solidification: the freshly prepared

uncured epoxy did not show any change at different cur-

ing agent ratio; in contrast, the clear feature in the data

with cured epoxy demonstrates that they correspond to

the real wettability of matrix to glass fiber after wetting

and solidification stages. This is reasonable because the

varying ratio of curing agent to epoxy changes the popu-

lation of the functional groups such as amino group. We

believe that correct contact angle measurement with ep-

oxy depends on whether the system is fully equilibrated,

especially for the very viscous polymers. The inverse

trend of the contact angle and IFSS demonstrates that

IFSS increases when the wettability of matrix to fibers is

improved.

FIG. 2. Plots of matrix mechanical properties versus the ratio of curing

agent to epoxy. (a) Matrix modulus; (b) matrix yield strength; and (c)

matrix fracture strength.

1460 POLYMER COMPOSITES—-2010 DOI 10.1002/pc

Properties of Fiber Composite at Different FiberSurface Treatment

Micro-Failure Modes. Keeping the curing agent ratio Rat the optimum value of 34:100 (w/w), the tensile meas-urements of fiber composites with different fiber surfacetreatment were conducted, and the typical micrographs formicrofailure modes are displayed in Fig. 5a–c. By usingthe OTS coated fibers with increasing amount of ozonetreatment, the microfailure modes at the interface changefrom complete failure, to partial failure, and to nonfailure.This is also reflected by the pattern of the interfacial shearstress concentration in the polarized optical micrographs(the bottom part of the images in the left column in

Fig. 5). For the OTS coated fibers without ozone treat-

ment, the crack propagates along the fiber/matrix interface

all the time, and the failure mode is fiber pulled-out, as

shown in Fig. 5a. However, for the fiber with 3 min of

ozone treatment, the crack penetrates into the matrix after

propagating along the interface for some distance.

Although the failure mode is still fiber pulled-out, shown

in Fig. 5b, the length of the fiber pulled-out is shorter.

This indicates a stronger adhesion between the fiber and

matrix. For the fiber with even longer ozone treatment

time, i.e., with 6 min of ozone treatment, there is no sur-

face debonding (Fig. 5c). These results demonstrate that

the effect of enhanced adhesion alters the local interfacial

FIG. 3. Typical micrographs for microfailure modes with changing curing agent ratio to epoxy. For (a)–(e),

the images correspond to curing agent ratio of 24:100, 26–30:100, 32–38:100, 40–44:100, and 46–48:100 (w/

w), respectively. In each group of images, the first two images are captured at low strain, containing optical

micrograph (the first image) and polarized optical micrograph (the second image). The last image is captured

at high strain after crack propagating. [Color figure can be viewed in the online issue, which is available at

www.interscience.wiley.com.]

DOI 10.1002/pc POLYMER COMPOSITES—-2010 1461

failure mode, which has been demonstrated previously by

our simulation [11].

IFSS and Wettability. The data of IFSS at different

ozone treatment time for fibers are plotted in Fig. 6 (rep-

resented by &). The interfacial shear strength for sample

with OTS preozone treated fibers is only 3.5 6 1.6 MPa.

The value of IFSS increases monotonously with increas-

ing time of ozone treatment, demonstrating the increased

interfacial adhesion. For the preozone treated fiber with

self-assembled monolayer of OTS, the direct interaction

of the epoxy with the glass fiber surface is screened by

the long alkyl chain, resulting in a very low interfacial

adhesion. The ozone treatment makes the coating oxi-

dized, generating more and more polar groups (carboxyl

group) on the surface [30], and promotes the binding of

the epoxy matrix and the fiber.

The data of contact angle of epoxy on the fiber surface

at different ozone treatment time are also shown in Fig. 6

(represented by *). In sharp contrast with the IFSS data,

a monotonous decrease of contact angle (h) with the pro-

longed ozone treatment time is discovered. The compari-

son between these two sets of data demonstrates that the

improved wettability by ozone treatment for fibers

enhanced the interfacial adhesion between the glass fiber

and epoxy matrix.

Relationship Between the Work of Adhesion andInterfacial Shear Strength

Although the epoxy matrix shows a change of interfa-

cial wettability to glass fiber at different curing agent ratio

R, its solid surface energy was found to vary little. By the

method of sessile drop test, the surface energy of the

FIG. 4. Plots of interfacial adhesion parameters versus the ratio of cur-

ing agent to epoxy. (a) IFSS; and (b) contact angle (h).

FIG. 5. Typical micrographs for microfailure modes with different fiber surface treatment. For (a)–(c), the

images correspond to the time of ozone treatment 0, 3, and 6 min, respectively. In each group of images, for the

left images, the top is optical micrograph, and the bottom is polarized optical micrograph. The strain levels for

capturing the images are as follows: (a) 2.5%, 8.0% and fracture; (b) 2.5%, 8.6% and fracture; and (c) 2.6%, 8.0%

and fracture. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com.]

1462 POLYMER COMPOSITES—-2010 DOI 10.1002/pc

investigated solid matrix (cS) for various curing agent

ratios was measured to be an average value of 36.4 6 0.8

mN�m21. For further data processing, this value of cS and

h was adopted in the determination of the work of adhe-

sion (Wa) by Young-Dupre equation.

The value of IFSS as a function of Wa for varying cur-

ing agent ratio as well as for different fiber surface treat-

ment are plotted together in Fig. 7. Both of these two sets

of data show that the IFSS values increase monotonously

with the work of adhesion in both cases, and there exists

a good consistence between the data for these two situa-

tions. The data can be fitted by a linear relation consider-

ably: sIFSS ¼ 2.9Wa 2 169, where sIFSS denotes interfa-

cial shear strength (IFSS) with MPa as unit and the unit

for Wa is mJ�m22. For the current system, such a relation

can be expressed by an empirical equation: sIFSS ¼ kWa

2 b. According to Nardin and Schultz [35, 36]:

s ¼ Em

Ef

� �1=2Wa

kð3Þ

where s and Wa denote the interfacial shear strength and

the work of adhesion, Em and Ef are the moduli of the

matrix and fiber, respectively, and k is the equilibrium

interatomic distance at the interface between matrix and

fiber. In Eq. 3, Em takes the average value of the moduli

of the matrix in Fig. 2a (Em � 1.7 GPa), and Ef takes the

average value of the moduli of the fiber uncoated and

coated in Table 1 (Ef � 45.7 GPa). There is as follows:

k ¼ 0:193Wa

sð4Þ

Substitute the data in Fig. 7 (s and Wa) into Eq. 4, theequilibrium interatomic distance at the interface k is

obtained, which ranges from 0.3 to 0.6 nm, in consistance

with the reported value [36], except for the particular

value in the case of the matrix and coated fiber without

ozone treated (3.2 nm) because of the extremely weak

interfacial adhesion.

CONCLUSIONS

Single-fiber composite tensile tests and surface wett-

ability tests were conducted to study the interfacial adhe-

sion behaviors and the mechanical properties by either

changing the curing agent ratio or the fiber surface treat-

ment. The failure mode and the wettability of polymer ma-

trix on glass fibers have been studied systematically. The

major finding is the correlation between the work of adhe-

sion and the interfacial shear strength. By changing the ra-

tio of the curing agent to epoxy matrix, good correlations

between the matrix mechanical properties, such as yield,

fracture strength, and IFSS were found. They all show

their maximum values around stoichiometric ratio of

34:100 (w/w). So did the wettability between matrix and

fibers. Such a correlation was further evidenced in the mo-

notonous dependence of IFSS on the work of adhesion, by

surface treatment of the glass fibers via self-assembled

monolayer technique and the accurate controlled ozone

treatment of the monolayer. Our data proved the linear

relationship between the interfacial shear strength and the

work of adhesion. Furthermore, the equilibrium intera-

tomic distance at the interface was evaluated.

REFERENCES

1. V. Dutschk, E. Pisanova, S. Zhandarov, and B. Lauke,

Mech. Compos. Mater., 34(4), 309 (1998).

FIG. 6. Plots of interfacial adhesion parameters (IFSS, represented by

&, and contact angle, represented by *) versus the time of ozone treat-

ment for fibers.

FIG. 7. Dependence of IFSS on the work of adhesion (Wa). Data from

experiments of changing curing agent ratio to epoxy and different fiber

surface treatment are represented by & and *, respectively.

DOI 10.1002/pc POLYMER COMPOSITES—-2010 1463

2. S.J. Park and S.G. Lee, J. Colloid Interface Sci., 228(1), 90(2000).

3. E. Pisanova and E. Mader, J. Adhes. Sci. Technol., 14(3),415 (2000).

4. G.J. Nam, H. Kim, and J.W. Lee, Polym. Compos., 24(3),487 (2003).

5. E. Feresenbet, D. Raghavan, and G.A. Holmes, J. Adhes.,79(7), 643 (2003).

6. E. Mader, S. Melcher, J.W. Liu, S.L. Gao, A.D. Bianchi, S.

Zherlitsyn, and J. Wosnitza, J. Mater. Sci., 42(19), 8047

(2007).

7. G.A. Holmes, R.C. Peterson, D.L. Hunston, and W.G.

McDonough, Polym. Compos., 28(5), 561 (2007).

8. P.W.J. Van den Heuvel, M.K. Wubbolts, R.J. Young, and T.

Peijs, Compos. Part A, 29(9/10), 1121 (1998).

9. T. Okabe, N. Takeda, Y. Kamoshida, M. Shimizu, and W.A.

Curtin, Compos. Sci. Technol., 61(12), 1773 (2001).

10. H.Z. Li, Y.X. Jia, S.F. Luan, Q. Xiang, C.C. Han, G. Mam-

timin, Y.C. Han, and L.J. An, Polym. Compos., 29(9), 964(2008).

11. L.L. Sun, Y.X. Jia, F.D. Ma, J. Zhao, and C.C. Han, Macro-mol. Mater. Eng., 293(3), 194 (2008).

12. A. Kelly and W.R. Tyson, J. Mech. Phys. Solids, 13(6), 329(1965).

13. K.D. Jones and A.T. Dibenedetto, Compos. Sci. Technol.,51(1), 53 (1994).

14. J.M. Park, J.W. Kim, and K. Goda, Compos. Sci. Technol.,60(3), 439 (2000).

15. L. Greszczuk, Interfaces in Composites, STP 452, American

Society for Testing and Materials, Philadelphia, PA, 42

(1969).

16. G. Desarmot and J.P. Favre, Compos. Sci. Technol., 42(1–3), 151 (1991).

17. B. Miller, P. Muri, and L. Rebenfeld, Compos. Sci. Technol.,28(1), 17 (1987).

18. V. Rao, P. Herrera-Franco, A.D. Ozzello, and L.T. Drzal,

J. Adhes., 34(1), 65 (1991).

19. P. Zinck, H.D. Wagner, L. Salmon, and J.F. Gerard, Poly-

mer, 42(12), 5401 (2001).

20. O.N. Tretinnikov and Y. Ikada, Langmuir, 10(5), 1606

(1994).

21. F. Hoecker and J. Karger-Kocsis, J. Appl. Polym. Sci.,59(1), 139 (1996).

22. J.H. Clint, Curr. Opin. Colloid Interface Sci., 6(1), 28

(2001).

23. A. Bismarck, M.E. Kumru, B. Song, J. Springer, E. Moos,

and J. Karger-Kocsis, Compos. Part A, 30(12), 1351 (1999).

24. A. Bismarck, D. Richter, C. Wuertz, and J. Springer, Col-

loids Surf. A, 159(2/3), 341 (1999).

25. A. Bismarck, D. Richter, C. Wuertz, M.E. Kumru, B. Song,

and J. Springer, J. Adhes., 73(1), 19 (2000).

26. J.M. Park, D.S. Kim, J.W. Kong, M. Kim, W. Kim, and I.S.

Park, J. Colloid Interface Sci., 249(1), 62 (2002).

27. S.N. Patankar, J. Mater. Sci. Lett., 10(20), 1176 (1991).

28. C.Y. Hui, S.L. Phoenix, and D. Shia, Compos. Sci. Technol.,

57(12), 1707 (1998).

29. S.A. Kulkarni, B.A. Kakade, I.S. Mulla, and V.K. Pillai,

J. Colloid Interface Sci., 299(2), 777 (2006).

30. L. Hong, H. Sugimura, T. Furukawa, and O. Takai, Lang-muir, 19(6), 1966 (2003).

31. S.F. Luan, H.Z. Li, Y.X. Jia, L.J. An, Y.C. Han, Q. Xiang,

J. Zhao, J.X. Li, and C.C. Han, Polymer, 47(17), 6218

(2006).

32. A. Khalili and K. Kromp, J. Mater. Sci., 26(24), 6741 (1991).

33. B. Song and J. Springer, J. Colloid Interface Sci., 184(1), 64(1996).

34. A.J. Lesser, Polym. Compos., 18(1), 16 (1997).

35. M. Nardin and J. Schultz, Compos. Interface, 1(1), 172 (1993).

36. M. Nardin and J. Schultz, Langmuir, 12(17), 4238 (1996).

1464 POLYMER COMPOSITES—-2010 DOI 10.1002/pc