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ASTM Selected Technical Papers
Effects of Defects in Composite Materials
By
DJ Wilkins
DJ Wilkins
1
Engineering staff specialist
,
General Dynamics
,
Fort Worth, Texas
;
symposium chairman
.
Search for other works by this author on:
ISBN-10:
0-8031-0218-6
ISBN:
978-0-8031-0218-7
No. of Pages:
281
Publisher:
ASTM International
Publication date:
1984

Any micromechanical theory for damage accumulation and ultimate failure in composites must depend on a knowledge of the detailed stress distribution in the damaged state. Lack of this knowledge has been a major roadblock to progress in this field. A shear lag approach to this problem has been proposed by Hedgepeth and Van Dyke for unidirectionally reinforced composites, but it is of limited utility because it contains an unknown parameter.

This paper discusses an experimental technique for finding stress distributions in damaged composites with the aid of an electric analogue. In this approach, a current is passed through a model employing conducting rods to represent fibers and a liquid electrolyte to represent the matrix. The potential distribution in the model is analogous to the longitudinal displacement distribution in the composite, and transverse currents are analogous to shear forces. The analogue is employed in the paper to evaluate the unknown parameter in the Hedgepeth and Van Dyke equation.

1.
Weibull
,
W.
, “
A Statistical Theory for the Strength of Materials
,”
Ingeniorsvetenskapakademiens
, Handlinger Nr. 151,
1939
.
2.
Smith
,
R. L.
,
Proceedings Royal Society
,
London
, Vol.
A372
,
1980
, pp. 539-553.
3.
Batdorf
,
S. B.
,
Journal of Reinforced Plastics and Composites
 0731-6844, Vol.
1
,
1982
, p. 165.
4.
Brussat
,
T. R.
and
Westmann
,
R. A.
,
International Journal of Solids and Structures
 0020-7683, Vol.
11
,
1975
, pp. 665-677.
5.
Eringen
,
A. C.
and
Kim
,
B. S.
,
Letters in Applied and Engineering Sciences
, Vol.
2
,
1974
, pp. 69-89.
6.
Dow
,
N. F.
, “
Study of Stresses Near a Discontinuity in a Filament-Reinforced Composite Metal
,” Space Mechanics Memo #102,
General Electric Space Science Laboratories
,
01
1961
.
7.
Muki
,
R.
and
Sternberg
,
E.
, “
Load-Absorption by a Discontinuous Filament in a Fiber-Reinforced Composite
,”
Journal of Applied Mathematics and Physics (Zeitschrift für Angewandt Mathematik und Physik)
, Vol.
22
, Fasc.
5
1971
.
8.
Ford
,
E. F.
, “
Stress Analysis of a Broken Fiber Imbedded in an Elastic Medium
,” Technical Report No. 1,
NSF
, GH-33576,
06
1973
.
9.
Hedgepeth
,
J. M.
, “
Stress Concentrations in Filamentary Structures
,” NASA TN D882,
National Aeronautics and Space Administration, Langley Research Center
1961
.
10.
Ko
,
W. L.
,
Nagy
,
A.
,
Francis
,
P. H.
, and
Lundholm
,
U. S.
,
Engineering Fracture Mechanics
 0013-7944, Vol.
8
,
1976
, pp. 415-422.
11.
Oh
,
Kong P.
,
Journal of Composite Materials
 0021-9983, Vol.
13
,
10
1979
, pp. 311-328.
12.
Goree
,
J. G.
and
Gross
,
R. S.
,
Engineering Fracture Mechanics
 0013-7944, Vol.
13
, pp. 563-578.
13.
Hedgepeth
,
J. M.
and
Van Dyke
,
P.
,
Journal of Composite Materials
 0021-9983, Vol.
1
,
1967
, pp. 294-309.
14.
Batdorf
,
S. B.
,
Journal of Applied Mechanics
 0021-8936, Vol.
50
,
03
1983
, pp. 190-193.
15.
Batdorf
,
S. B.
,
Engineering Fracture Mechanics
 0013-7944, Vol.
18
, No.
6
,
1983
, pp. 1207-1210.
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