Abstract

Growing application of composite materials in airframe structures tends to make significant use of bonded constructions. Despite the large work that has been done on adhesive characterization over previous years, various certification-related issues arise in these applications. The available test methods for determining the in situ properties of an adhesive joint for use in the design must be clarified for thick bondlines, where there is a lack of readily available data. Results from three test methods indicated a decrease in the apparent shear strength as the bondline thickness was increased. The apparent shear strength given by the test methods investigated was found to be highly dependent on the adherend bending stiffness, which directly effects the peel stress distributions in the adhesive layer. In the adhesive strength comparisons as a function of test method, it was found that the thin-adherend tests gave different comparative results than the thick-adherend tests, which were primarily a function of the high peel stresses in the thin-adherend joints. This combined state of stress does not give a true view of the apparent shear stress of the adhesive, but rather an indication of the adhesive behavior under this type of combined loading. It is recommended that thick adherends be used when comparing different adhesive systems for apparent shear strength, and that thin adherends should be used for qualitative tests only.

References

1.
Kuno
,
J. K.
,
Structural Adhesives and Bonding, Proceedings of the Structural Adhesives Bonding Conference
,
El Segundo, CA
,
1979
.
2.
Tsai
,
M. Y.
,
Morton
,
J.
,
Krieger
,
R. B.
, and
Oplinger
,
D. W.
, “
Experimental Investigation of the Thick-Adherend Lap Shear Test
,”
Journal of Advanced Mechanics
,
04
1996
, pp.
28
-
36
.
3.
Vinson
,
J. K.
, “
Adhesive Bonding of Polymer Composites
,”
Polymer Engineering and Science
, Vol.
29
, No.
19
,
1989
, pp.
1325
-
1331
.
4.
MILITARY-HANDBOOK-17-3E, DOD Coordination Working Draft
. “Chapter 5—
Structural Behavior of Joints
.”
5.
ASTM Standard D1002:
Standard Test Method for Apparent Shear Strength of Single-Lap-Joint Adhesively Bonded Metal Specimens by Tension Loading
,
Annual Book of ASTM Standards
, Vol.
15.06
,
ASTM International
,
West Conshohocken, PA
,
1989
.
6.
ASTM Standard D3165:
Standard Test Method for Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated Assemblies
,
Annual Book of ASTM Standards
, Vol.
15.06
,
ASTM International
,
West Conshohocken, PA
,
1997
.
7.
ASTM Standard D5656:
Standard Test Method for Thick-Adherend Metal Lap-Shear Joints for Determination of the Stress-Strain Behavior of Adhesives in Shear by Tension Loading
,”
Annual Book of ASTM Standards
, Vol.
15.06
,
ASTM International
,
West Conshohocken, PA
,
1997
.
8.
Krieger
,
R. B.
, Jr.
, “
Stress Analysis Concepts for Adhesive Bonding of Aircraft Primary Structure
.”
Adhesively Bonded Joints: Testing, Analysis, and Design, ASTM STP 981
,
W. S.
Johnson
, Ed.,
ASTM International
,
West Conshohocken, PA
,
1988
, pp.
264
-
275
.
9.
Volkerson
,
O.
, “
Die Neitkraftverteilung in Zugbeanspruchten Neitverbindungen mit Konstanten Laschenquerschnitten
,”
Luftfahrtforschung
, Vol.
15
,
1938
, pp.
4
-
47
.
10.
Goland
,
M.
and
Reissner
,
E.
, “
The Stresses in Cemented Joints
,”
Journal of Applied Mechanics
,
03
1944
, pp. A.17-A.27.
11.
Kutscha
,
D.
, “
Mechanics of Adhesive-Bonded Lap-Type Joints: Survey and Review
,”
Technical Report
AFML-TDR-64-298,
1964
.
12.
Kutscha
,
D.
and
Hofer
,
K. E.
, Jr.
, “
Feasibility of Joining Advanced Composite Flight Vehicles
,”
Technical Report
AFML-TR-68-391,
1969
.
13.
Adams
,
R. D.
and
Wake
,
W. C.
,
Structural Adhesive Joints in Engineering
,
Elsevier Applied Science Publishers
,
London, England
,
1984
.
14.
Guess
,
T. R.
,
Allred
,
R. E.
, and
Gerstle
,
F. P.
, Jr.
, “
Comparison of Lap Shear Tests
,”
Journal of Testing and Evaluation
, Vol.
5
, No.
3
,
1977
, pp.
84
-
93
.
15.
Hart-Smith
,
L. J.
, “
Adhesive-Bonded Single-Lap Joints
,”
Douglas Aircraft Company, NASA Langley Report
CR 112236,
1973
.
16.
Hart-Smith
,
L. J.
, “
Adhesive-Bonded Double-Lap Joints
,”
Douglas Aircraft Company, NASA Langley Report
CR 112235,
1973
.
17.
Hart-Smith
,
L. J.
, “
Adhesive-Bonded Scarf and Stepped-Lap Joints
,”
Douglas Aircraft Company, NASA Langley Report
CR 112237,
1973
.
18.
Hart-Smith
,
L. J.
, “
Analysis and Design of Advanced Composite Bonded Joints
,”
Douglas Aircraft Company, NASA Langley Report
CR 2218,
1974
.
19.
Oplinger
,
D. W.
,
Proceedings of the Fourth Army Materials Technology Conference—Advances in Joining Technology
,
09
1975
.
20.
Oplinger
,
D. W.
, “
Effects of Adherend Deflections in Single Lap Joints
,”
International Journal of Solids and Structures
, Vol.
31
,
1994
, pp.
2565
-
2587
.
21.
Yang
,
C.
,
Pang
,
S. S.
, and
Griffen
,
S. A.
, “
Failure Analysis of Adhesive-Bonded Double-Lap Joints Under Cantilevered Bending
,”
Polymer Engineering and Science
, Vol.
31
,
1992
, pp.
533
-
538
.
22.
Yang
,
C.
and
Pang
,
S. S.
, “
Stress-Strain Analysis of Single-Lap Composite Joints under Cylindrical Bending
,”
Composites Engineering
, Vol.
3
,
1993
, pp.
1051
-
1063
.
23.
Post
,
D.
,
Czarnek
,
R.
,
Wood
,
J. D.
, and
Job
,
D.
, “
Deformations and Strains in a Thick Adherend Lap Joint
,”
Adhesively Bonded Joints: Testing, Analysis and Design
, ASTM STP 981,
ASTM International
,
West Conshohocken, PA
,
1988
, pp.
107
-
118
.
24.
Kassapoglou
,
C.
and
Adelmann
,
J. C.
, “
KGR-1 Thick Adherend Specimen Evaluation for the Determination of Adhesive Mechanical Properties
,”
23rd International SAMPE Technical Conference
, October 21–24, 1991.
25.
Yang
,
C.
,
Huang
,
H.
, and
Tomblin
,
J. S.
, “
Evaluation and Adjustments of ASTM D5656-Standard Test Method for Thick-Adherend Metal Lap-Shear Joints for Determination of the Stress-Strain Behavior of Adhesives in Shear by Tension Loading
,”
Journal of Testing and Evaluation
, Vol.
29
, No.
1
,
01
2001
, pp.
36
-
43
.
26.
Huang
,
H.
,
Yang
,
C.
,
Tomblin
,
J. S.
, and
Harter
,
P.
, “
Stress and Failure Analyses of Adhesive-Bonded Composite Joints using ASTM D3165 Specimens
,”
Proceedings of American Society for Composites 15th Annual Technical Conference
,
College Station
, September 24–27, 2000, pp.
599
-
608
.
27.
Tomblin
,
J.
,
Yang
,
C.
, and
Harter
,
P.
, “
Investigation of Thick Bondline Adhesive Joints
,” DOT/FAA/AR-01/33,
Federal Aviation Administration, National Technical Information Service
,
Springfield, VA
,
2001
.
This content is only available via PDF.
You do not currently have access to this content.