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ASTM Selected Technical Papers
Composite Reliability
By
EM Wu
EM Wu
1
Washington University
,
St. Louis, Mo. 63130
;
symposium chairman
.
Search for other works by this author on:
ISBN-10:
0-8031-0309-3
ISBN:
978-0-8031-0309-2
No. of Pages:
646
Publisher:
ASTM International
Publication date:
1975

Variability in composite tension-test values limits the application of advanced composite materials to structural design loads far below the capabilities inherent to the reinforcing fibers. Failure probabilities of boron and graphite filaments on the low-strength side of the skewed distribution contribute to composite fracture initiation early in the loading cycle. Dispersion in composite test values at these low levels imposes restrictions on allowable design values to conform to the minimum in the test data population. Prestressing the prepreg materials affects a fiber strength property improvement by prebreaking the filaments at the defect sources of low load failure. Increases in “B” design allowable levels for boron and graphite-epoxy material systems are shown to relate to reductions in fiber strength dispersions accompanied by increases in the average values. Projections of composite “B” allowables to 297 ksi are made for defect-free filaments.

1.
Military Standardization Handbook: Metallic Materials and Elements for Aerospace Vehicle Structures
,” Vol.
2
of two volumes, MIL-HDBK-5B,
09
1971
.
2.
Patent Pending #390,595,
22
08
1973
.
3.
Mills
,
G.
and
Dauksys
,
R.
, “
Effects of Prestressing Boron/Epoxy Prepreg on Composite Strength Properties
,”
Journal, American Institute of Aeronautics and Astronautics
 0001-1452, Vol.
2
, No.
11
,
11
1973
, pp. 1459–1460.
4.
Effects of Prestressing Boron/Epoxy Prepreg on Composite Strength Properties
,” AIAA Paper No. 73-382, American Institute of Aeronautics and Astronautics-American Society of Mechanical Engineers-Society of Aeronautical Engineers, 14th Structures, Structural Dynamics, and Materials Conference,
Williamsburg, Va.
, 20–22 March 1973.
5.
Mills
,
G.
,
Brown
,
G.
, and
Waterman
,
D.
, “
Prestressing of Boron and Graphite Epoxy Prepreg for Composite Strength Improvement
,” Technical Report AFML-TR-73-118,
Air Force Materials Laboratory
, Dayton, Ohio,
06
1973
.
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