Abstract
This paper is concerned with compression testing of thin-walled graphite/epoxy structures and the development of empirical stability methods of analysis. The laminates of the structures tested were T-300/5208 graphite/epoxy with arbitrary, symmetrical stacking sequences. Crippling tests were performed on flat plates to generate no-edge-free and one-edge-free empirical crippling curves for use in buckling analysis of thin-walled graphite/epoxy short columns. Crippling tests of square tubes confirmed correlation with flat plates. Short-column tests of similar square tubes and tests of lsection members substantiated use of the Johnson short-column method. Ultimate compression tests were performed for most laminates, and nonlinear stress-strain curves were recorded in all cases.
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Abbreviations
- A :
-
total cross-sectional area
- b :
-
width of plate element
- D ij :
-
flexural elastic constants
- E c :
-
compressive modulus of elasticity
- E t :
-
tensile modulus of elasticity
- F cc :
-
crippling stress
- F cr :
-
theoretical elastic-buckling stress
- F cri :
-
incipient-buckling stress
- F crnef :
-
no-edge free theoretical elastic-buckling stress
- F crief :
-
one-edge-free theoretical elastic-buckling stress
- F cu :
-
ultimate compressive strength
- F tu :
-
ultimate tensile strength
- L :
-
length of composite-test specimen
- \(\bar L\) :
-
total length of test specimen including end supports
- L′ :
-
effective length,\(\bar L/\sqrt C \), whereC is the end-fixity coefficient and is equal to 3.6 for fixed-ended test specimens in testing machine
- P cr :
-
theoretical elastic-buckling load
- P cri :
-
incipient-buckling load
- P cc :
-
crippling load
- P co :
-
column load
- n :
-
exponent in eq (3)
- t :
-
thickness
- ν/o :
-
fiber-volume percent
- α:
-
coefficient in eq (3)
- ɛc :
-
compressive strain
- ɛcu :
-
ultimate compressive strain
- ξ12 :
-
major Poisson's ratio
- ϱ min :
-
minimum radius of gyration of total cross section
- σc :
-
compressive stress
References
Spier, E.E. and Klouman, F.L., “Empirical Crippling Analysis of Graphite/Epoxy Laminated Plates,” Composite Materials: Testing and Design (4th Conf.), ASTM,ASTM STP 617 (1977).
Spier, E.E. and Klouman, F.L., “Post Buckling Behavior of Graphite/Epoxy Laminated Plates and Channels,” Proc. Army Symp. Solid Mechanics, 1976—Composite Materials: The Influence of Mechanics of Failure on Design, Army Materials and Mechanics Research Center, Watertown, MA,AMMRC MS 76-2 (Sept. 1976).
Spier, E.E. and Klouman, F.L., “Ultimate Compressive Strength and Nonlinear Stress-Strain Curves of Graphite/Epoxy Laminates,” Proc. 8th Natl. SAMPE Conf., “Bicentennial of Materials Progress—Part II”, Seattle, WA (Oct. 1976).
May, C.L., “Fabrication Methods for Graphite/Epoxy Tubular Structures,” unpublished.
Advanced Composites Design Guide, Vol. II—Analysis, Air Force Materials Lab., Advanced Development Division, Dayton, OH, Table 2.2.2-I (Jan. 1973).
Gerard, G., Structural Stability Theory, McGraw-Hill, Sec. 3.9 (1962).
Spier, E.E., “Crippling/Column Buckling Analysis and Test of Graphite/Epoxy-stiffened Panels,” AIAA Paper 75-753, presented AIAA/ASME/SAE 16th Structures, Structural Dynamics, and Materials Conf., Denver, CO (May 27–29, 1975).
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Spier, E.E. Stability of graphite/epoxy structures with arbitrary symmetrical laminates. Experimental Mechanics 18, 401–408 (1978). https://doi.org/10.1007/BF02325055
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DOI: https://doi.org/10.1007/BF02325055