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ASTM Selected Technical Papers
Composite Materials: Testing and Design (Fourth Conference)
By
JG Davis, Jr Jr
JG Davis, Jr Jr
1
National Aeronautics and Space Administration-Langley Research Center
,
Hampton, Va. 23665
;
conference chairman
.
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ISBN-10:
0-8031-4490-3
ISBN:
978-0-8031-4490-3
No. of Pages:
540
Publisher:
ASTM International
Publication date:
1977

This paper describes the analytical/experimental correlation study performed to develop an understanding of the behavior of notched boron/epoxy laminates subjected to tension/tension fatigue loading. The static failure analysis of notched laminates used herein treats the following modes of failure: axial cracking in the load direction, and transverse cracking across the specimen. The “mechanistic wearout” fatigue analysis uses this static failure model and embodies the concept that material properties in the notch region are continually changing with cyclic loading and that, if these properties are known at a given time, they could be used in the static failure analysis to compute residual strength and preferred mode of crack propagation. In order to verify the fatigue model, an experimental program of limited scope was undertaken to obtain boron/epoxy lamina static and fatigue data (longitudinal and transverse tension and in-plane shear), unnotched [02/±45]s laminate static data, and notched [02/±45]s laminate static and fatigue data. Laminate fatigue behavior was determined from lamina fatigue data, and analysis predictions were compared with the notched-laminate fatigue data. The specific phenomena of interest are the initiation of fatigue damage and its growth as a function of load cycles, fatigue life and mode of failure, and the residual strength after a predetermined number of cycles and the corresponding mode of failure. Certain predicted phenomena such as the increase in residual strength after fatigue loading and both axial and transverse damage growth were observed experimentally. However, correlation of theory and experiment was hampered by the following factors: delamination of the 0-deg surface layers in the region of the longitudinal projection of the notch diameter, lack of statistically significant data base for lamina fatigue properties in general, and absence of lamina axial compression fatigue data in particular. The principal deficiency appears to be the lack of a capability to predict growth of delaminations. Therefore, the interplay of stacking sequence and various failure modes needs to be investigated analytically and experimentally in detail.

1.
McLaughlin
,
P. V.
, Jr.
,
Kulkarni
,
S. V.
,
Huang
,
S. N.
, and
Rosen
,
B. W.
, “
Fatigue of Notched Fiber Composite Laminates, Part I: Analytical Model
,” Technical Report NASA CR-132747,
National Aeronautics and Space Administration, Langley Research Center
, Hampton, Va.,
03
1975
.
2.
Durchlaub
,
E. C.
and
Freeman
,
R. B.
, “
Design Data for Composite Structure Safelife Prediction
,” Technical Report AFML-Tr-73-225,
Air Force Materials Laboratory
, Dayton, Ohio,
03
1974
.
3.
Kulkarni
,
S. V.
and
Rosen
B. W.
, “
Design Data for Composite Structure Safelife Prediction: Analysis Evaluation
,” Technical Report TFR/2221,
Materials Sciences Corporation
, Blue Bell, Pa.
08
1973
.
4.
Rosen
,
B. W.
and
Zweben
,
C. H.
, “
Tensile Failure Criteria for Fiber Composite Materials
,” Technical Report NASA CR-2057,
National Aeronautics and Space Administration, Langley Research Center
, Hampton, Va.,
1972
.
5.
Zweben
,
C. H.
in
Analysis of the Test Methods for High Modulus Fibers and Composites
, ASTM STP 521,
1973
, pp. 65-97;
also,
Materials Sciences Corporation Report
,
1972
.
6.
Waddoups
,
M. E.
,
Eisenmann
,
J. R.
, Jr.
, and
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,
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,
Journal of Composite Materials
 0021-9983, Vol.
5
,
10
1971
, pp. 446-454.
7.
Whitney
,
J. M.
and
Nuismer
,
R. J.
,
Journal of Composite Materials
 0021-9983, Vol.
8
,
07
1974
, pp. 253-265.
8.
Kulkarni
,
S. V.
,
McLaughlin
,
P. V.
, Jr.
, and
Pipes
,
R. B.
, “
Fatigue of Notched Fiber Composite Laminates, Part II: Analytical and Experimental Evaluation
,” Technical Report NASA CR-145039,
National Aeronautics and Space Administration, Langley Research Center
, Hampton, Va.
1976
.
9.
Hofer
,
K. E.
 et al
, “
Development of Engineering Data on the Mechanical and Physical Properties of Advanced Composite Materials
,” Part II, Technical Report AFML-TR-72-205,
Air Force Materials Laboratory
, Dayton, Ohio,
02
1974
.
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