Adhesives used for bonded-in steel or composite pultruded rods and plate to make connections in timber structures are commonly room temperature cure adhesives. The room temperature cure, applied without pressure, thixotropic, and shear thinning characteristics of the adhesives, is for ease of application when repairs and reinforcement are being made in situ in the field. The room temperature cure adhesive may not fully cross-link and this may cause brittleness. Therefore to improve the toughness properties of such adhesives, nanoparticles can be added. This paper reports the experimental investigation carried out on the fracture toughness of three thixotropic and room temperature cured epoxy-based adhesives formulated specifically for in situ timber bonding, namely, CB10TSS (standard adhesive), Albipox is CB10TSS with the addition of nanodispersed carboxyl-terminated butadiene acrylonitrile (CTBN), and Timberset is an adhesive formulation containing ceramic microparticles. The fracture toughness behavior of the adhesives was investigated using the Charpy impact test on unnotched and notched specimens conditioned at 20C/65%RH to evaluate notch sensitivity, and a single-edge notched beam (SENB) test was performed to evaluate the stress intensity factor KIC. The fracture surfaces were investigated using scanning electron microscopy. Under high impact rate, toughness was in the order of CB10TSS, Albipox, and Timberset. CB10TSS and Albipox were found to be ductile in the unnotched state and brittle when notched. Timberset was brittle in both unnotched and notched states. Under low strain rate (SENB) conditions the addition of CTBN significantly improved the fracture toughness of Albipox compared with CB10TSS and Timberset. Examination of the topography of the fractured surface revealed marked changes in crack propagation due to the addition of nano- or microfillers accounting for the variation in toughness properties.

References

1.
Ansell
,
M. P.
, and
Smedley
,
D.
, 2007, “
Bonded-In Technology for Structural Timber
,”
Proc of the Institution of Civil Engineering, Construction Materials
,
60
(3), pp.
95
98
.
2.
Harvey
,
K.
,
Ansell
,
M. P.
,
Mettem
,
C. J.
, and
Bainbridge
,
R. J.
, 2000, “
Bonded-in Pultrusions for Moment-Resisting Timber Connections
,”
Proceedings of the 33rd Meeting of Working Commission W18, CIB-W18
, Delft, The Netherlands, Aug 28–30,
University of Karlsruhe, Delft
,
The Netherlands
, Paper No. CIB-W18/33-7-11.
3.
Broughton
,
J. G.
, and
Hutchinson
,
A. R.
, 2001, “
Efficient Timber Connections Using Bonded-in GFRP Rods
,”
Proceedings of the International Conference on Composites in Construction
,
Figueiras
,
J.
,
Juvandes
,
L.
, and
Furia
,
R.
, eds.,
Balkema
, A. A. (Porto, Portugal), pp.
275
280
.
4.
Rosso
,
P.
, and
Ye
,
L.
, 2007, “
Epoxy/Silica Nanocomposites: Nanoparticle-Induced Cure Kinetics and Microstructure
,”
Macromol. Rapid Commun.
,
28
(
1
), pp.
121
126
.
5.
Bauer
,
F.
,
Decker
,
U.
,
Ernst
,
H.
,
Findeisen
,
M.
,
Langguth
,
H.
,
Mehnert
,
R.
,
Sauerland
,
V.
, and
Hinterwaldner
,
R.
, 2006, “
Functionalized Inorganic/Organic Nanocomposites as New Basic Raw Materials for Adhesives and Sealants Part 2
,”
Int. J. Adhes. Adhes.
,
26
(
7
), pp.
567
570
.
6.
Verchere
,
D.
,
Pascault
,
J. P.
,
Sautereau
,
H.
,
Moschiar
,
S. M.
,
Riccardi
,
C. C.
, and
Williams
,
R. J. J.
, 1991, “
Rubber-Modified Epoxies. 2. Influence of the Cure Schedule and Rubber Concentration on the Generated Morphology
,”
J. Appl. Polym. Sci.
,
42
(
3
), pp.
701
716
.
7.
Pearson
,
R. A.
, and
Yee
,
A. F.
, 1991, “
Influence of Particle-Size and Particle-Size Distribution on Toughening Mechanisms in Rubber-Modified Epoxies
,”
J. Mater. Sci.
,
26
(
14
), pp.
3828
3844
.
8.
Iijima
,
T.
,
Miura
,
S.
,
Fukuda
,
W.
, and
Tomoi
,
M.
, 1993, “
Effect of Cross-Link Density on Modification of Epoxy Resins by -Phenylmaleimide-Styrene Copolymers
,”
Eur. Polym. J.
,
29
(
8
), pp.
1103
1113
.
9.
Achary
,
P. S.
,
Latha
,
P. B.
, and
Ramaswamy
,
R.
, 1990, “
Room-Temperature Curing of CTBN-Toughened Epoxy Adhesive With Elevated-Temperature Service Capability
,”
J. Appl. Polym. Sci.
,
41
(
12
), pp.
151
162
.
10.
Bucknall
,
C. B.
, 1977, Toughened plastics, Applied Science.
11.
Kinloch
,
A. J.
, 1986,
Rubber-Toughened Thermosetting Polymers in Structural Adhesive
,
A. J.
Kinloch
, ed.,
Elsevier Applied Science
,
England.
12.
Wang
,
Z.
,
Massam
,
J.
, and
Pinnavaia
,
T. J.
, 2000,
Polymer Clay Nanocomposites
,
T. J.
Pinnavaia
and
G. W.
Beall
, eds.,
Wiley
,
New York.
13.
Ahmad
,
Z.
,
Ansell
,
M. P.
, and
Smedley
,
D.
, 2006, “
Influence of Nanofiller on Thermal and Mechanical Behaviour of DGEBA-Based Adhesives for Bonded-In Timber Connections
,”
Mech. Compos. Mater.
,
42
(
5
), pp.
419
430
.
14.
Min
,
B. G.
,
Stachurski
,
Z. H.
, and
Hodgkin
,
J. H.
, 1993, “
Microstructural Effects and the Toughening of Thermoplastic Modified Epoxy Resins
,”
J. Appl. Polym. Sci.
,
50
, pp.
1511
1518
.
15.
Scherzer
,
T.
, 1994, “
Characterization of Diol Modified Epoxy Resins by Near- and Mid-Infrared Spectroscopy
,”
J. Appl. Polym. Sci.
,
51
(
3
), pp.
491
502
.
16.
Miyagawa
,
H.
, and
Drzal
,
L. T.
, 2004, “
The Effect of Chemical Modification on the Fracture Toughness of Montmorillonite Clay/Epoxy Nanocomposites
,”
J. Adhes. Sci. Technol.
,
18
(
13
), pp.
1571
1588
.
17.
Haque
,
A.
,
Shamsuzzoha
,
M.
,
Hussain
,
F.
, and
Dean
,
D.
, 2003, “
S2-Glass/Epoxy Polymer Nanocomposites: Manufacturing, Structures, Thermal and Mechanical Properties
,”
J. Compos. Mater.
,
37
(
20
), pp.
1821
1837
.
18.
Achary
,
P. S.
,
Gouri
,
C.
, and
Ramamurty
,
R.
, 1991, “
Carboxyl-Terminated Poly(Propylene Glycol) Adipate-Modified Room Temperature Curing Epoxy Adhesive for Elevated Temperature Service Environment
,”
J. Appl. Polym. Sci.
,
42
, pp.
743
752
.
19.
Scarito
,
P. R.
, and
Sperling
,
L. H.
, 1979, “
Effect of Grafting on Phase Volume Fraction, Composition, and Mechanical-Behavior-Epoxy-Poly (N-Butyl Acrylate) Simultaneous Interpenetrating Networks
,”
Polym. Eng. Sci.
,
19
(
4
), pp.
297
303
.
20.
Oksman
,
K.
, and
Clemons
,
C.
, 1998, “
Mechanical Properties and Morphology of Impact Modified Polypropylene-Wood Flour Composites
,”
J. Appl. Polym. Sci.
,
67
, pp.
1503
1513
.
21.
Neilsen
,
L. E.
, 1974,
Mechanical Properties of Polymers and Composite
,
Dekker
,
New York
,
Vol. 2
.
22.
Manson
,
J. A.
, and
Sperling
,
L. H.
, 1974,
Polymer Blends and Composites
,
Plenum
,
New York
.
23.
Wu
,
C. L.
,
Zhang
,
M. Q.
,
Rong
,
M. Z.
, and
Friedrich
,
K.
, 2005, “
Silica Nanoparticles Filled Polypropylene: Effects of Particle Surface Treatment, Matrix Ductility and Particle Species on Mechanical Performance of the Composites
,”
Compos. Sci. Technol.
,
65
(
3–4
), pp.
635
645
.
24.
Ashby
,
M. F.
, and
Jones
,
D. R. H.
, 1980,
Engineering Materials: An Introduction to Their Properties and Applications
,
Pergamon
,
England
.
25.
Pugh
,
S. F.
, 1967, “
Physics Reviews: The Fracture of Brittle Materials
,”
Br. J. Appl. Phys.
,
18
, pp.
129
.
26.
Vincent
,
P. I.
, 1971,
Impact Test and Service Performance of Thermoplastics
,
Plastics Institution
,
London
.
27.
Neisen
,
L. E.
, 1962,
Mechanical Properties of Polymer
,
Van Nostrand Reinhold
,
New York
.
28.
Hojo
,
H.
,
Toyoshima
,
W.
,
Tamura
,
M.
, and
Kawamura
,
N.
, 1971, “
Short and Long-Term Strength Characteristics of Particulate-Filled Cast Epoxy
,”
Polym. Eng. Sci.
,
14
(
9
), pp.
604
609
.
29.
Ward
,
I. M.
, 1979,
Mechanical Properties of Solid Polymers
, 2nd Ed.,
Wiley
,
New York
.
30.
Griffith
,
A. A.
, 1920, “
The Phenomena of Rupture and Flow in Solids
,”
Proc. R. Soc. London, Ser. A
,
221
, pp.
163
198
.
31.
Irwin
,
G. R.
, 1964, “
Fractography of Highly Crosslinked Polymers
,”
ASME J. Eng. Power
,
86
, pp.
444
450
.
32.
Rezaifard
,
A. R.
,
Hodd
,
K. A.
, and
Barton
,
J. M.
, 1993,
Toughened Plastics I
(Advances in Chemistry Series
Vol. 233
),
C. K.
Riew
and
A. J.
Kinloch
, eds.,
American Chemical Society
,
Washington, DC
.
33.
Maxwell
,
D.
,
Young
,
R. J.
, and
Kinloch
,
A. J.
, 1984, “
Hybrid Particulate-Filled Epoxy Polymer
,”
J. Mater. Sci. Lett.
,
3
(
1
), pp.
9
12
.
34.
Kinloch
,
A. J.
,
Shaw
,
S. J.
,
Tod
,
D. A.
, and
Hunston
,
D. L.
, 1983, “
Deformation and Microstructure and Fracture Studies
,”
Polymer
,
24
(
10
), pp.
1341
1354
.
35.
Atsuta
,
M.
, and
Turner
,
D. T.
, 1982, “
Fractography of Highly Crosslinked Polymers
,”
J. Mater. Sci. Lett.
,
1
(4)
, pp.
167
169
.
36.
Cantwell
,
W. J.
,
Roulin-moloney
,
A. C.
, and
Kaiser
,
T.
, 1988, “
Fractography of Unfilled and Particulate-Filled Epoxy-Resins
,”
J. Mater. Sci.
,
23
(5)
, pp.
1615
1631
.
37.
Cantwell
,
W. J.
,
Smith
,
J. W.
,
Kausch
,
H. H.
, and
Kaiser
,
T.
, 1990, “
Examination of the Processes of Deformation and Fracture in a Silica-Filled Epoxy-Resin
,”
J. Mater. Sci.
,
25
(
1
), pp.
633
648
.
38.
Chou
,
C. J.
,
Vijayan
,
K.
,
Kirby
,
D.
,
Hiltner
,
A.
, and
Baer
,
E.
, 1988, “
Ductile-to-Brittle Transition of Rubber-Modified Polypropylene
,”
J. Mater. Sci.
,
23
, pp.
2521
2532
.
39.
D’almeida
,
J. R. M.
,
Cella
,
N.
, 2000, “
Analysis of the Fracture Behavior of Epoxy Resins Under Impact Conditions
,”
J. Appl. Polym. Sci.
,
77
(
11
), pp.
2486
2492
.
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