Skip to Main Content
Skip Nav Destination
ASTM Selected Technical Papers
Composite Materials: Fatigue and Fracture (Third Volume)
By
TK O'Brien
TK O'Brien
1
U.S. Army Aerostructures Directorate (AVSCOM), NASA Langley Research Center
,
Hampton, Virginia
;
symposium chairman and editor
.
Search for other works by this author on:
ISBN-10:
0-8031-1419-2
ISBN:
978-0-8031-1419-7
No. of Pages:
838
Publisher:
ASTM International
Publication date:
1991

Previous work by the authors has shown that it is possible to measure transverse displacements of both faces of a cracked lap shear (CLS) specimen accurately. In this work, this approach is extended so as to determine experimentally the Mode I behavior of the delamination. By considering the difference in the displacements of the two faces, a surface opening displacement (SOD) can be calculated. This SOD is related to the crack opening displacement (COD). It is shown, using the finite element method (FEM) analysis, that the SOD is not identical to the COD, but is uniquely related to it, and is very sensitive to changes in the COD. Experimentally derived SOD profiles at different positions along the width of the crack front are compared with scanning electron microscope examinations of the sectioned specimen, and good agreement is observed. It is shown that there is delayed opening of the crack as the specimen is loaded. The absolute values of the experimental and FEM analysis SOD profiles are in reasonable agreement, and it is shown that GI values can be calculated from the experimental results. The method is cumbersome and the results are difficult to interpret. However, once the low load profiles are established, the method can be used to monitor subcritical crack growth easily. In all three material systems tested, considerable subcritical crack growth (up to 4 mm) was measured, and the associated G values are 15 to 40% lower than Gc.

1.
O'Brien
,
T. K.
,
Murri
,
G. B.
, and
Salpekar
,
S. A.
, “
Interlaminar Shear Fracture Toughness and Fatigue Thresholds for Composite Materials
,”
Composite Materials: Fatigue and Fracture, Second Volume
, ASTM STP 1012,
Lagace
P. A.
, Ed.,
American Society for Testing and Materials
,
Philadelphia
,
1989
, pp. 222–250.
2.
Mall
,
S.
,
Yun
,
K. T.
, and
Kochhar
,
N. K.
, “
Characterization of Matrix Toughness Effect on Cyclic Delamination Growth in Graphite Fiber Composites
,”
Composite Materials: Fatigue and Fracture, Second Volume
, ASTM STP 1012,
Lagace
P. A.
, Ed.,
American Society for Testing and Materials
,
Philadelphia
,
1989
, pp. 296–310.
3.
Crews
,
J. H.
, Jr.
, and
Reeder
,
J. R.
, “
A Mixed-Mode Bending Apparatus for Delamination Testing
,” NASA Technical Memorandum 100662,
NASA Langley Research Center
,
Hampton, VA
,
08
1988
.
4.
O'Brien
,
T. K.
, “
Generic Aspects of Delamination in Fatigue of Composite Materials
,”
Journal, American Helicopter Society
, Vol.
32
, No.
1
.
01
1987
, pp. 13–18.
5.
Poursartip
,
A.
and
Chinatambi
,
N.
, “
Fatigue Growth, Deflections, and Crack Opening Displacements in Cracked Lap Shear Specimens
,”
Composite Materials: Testing and Design (Ninth Volume)
, ASTM STP 1059,
Garbo
S. P.
, Ed.,
American Society for Testing and Materials
,
Philadelphia
,
1990
, pp. 301–323.
6.
Broek
,
D.
,
Elementary Engineering Fracture Mechanics
, Third Revision,
Martinus Nijhoff Publishers
,
The Hague
,
1982
.
7.
Sih
,
G. C.
,
Paris
,
P. C.
, and
Irwin
,
G. R.
, “
On Cracks in Rectilinearly Anisotropic Bodies
,”
International Journal of Fracture Mechanics
, Vol.
1
,
1965
, pp. 189–202.
8.
Fleck
,
N. A.
, private communication,
1989
.
9.
Johnson
,
W. S.
, “
Stress Analysis of the Cracked Lap Shear Specimen: An ASTM Round Robin
,”
Journal of Testing and Evaluation
 0090-3973, Vol.
15
, No.
6
,
11
1987
, pp. 303–324.
10.
Brussat
,
T. R.
and
Chiu
,
S. T.
, “
Fracture Mechanics for Structural Adhesive Bonds—Final Report
,” AFML TR-77-163,
Air Force Materials Laboratory
, Wright Patterson Air Force Base, OH,
1977
.
This content is only available via PDF.
You do not currently have access to this chapter.
Close Modal

or Create an Account

Close Modal
Close Modal