Abstract
This paper describes the behaviour of a carbon-fibre reinforced epoxy composite when deformed in compression under high hydrostatic confining pressures. The composite consisted of 36% by volume of continuous fibres of Modmur Type II embedded in Epikote 828 epoxy resin. When deformed under pressures of less than 100 MPa the composite failed by longitudinal splitting, but splitting was suppressed at higher pressures (up to 500 MPa) and failure was by kinking. The failure strength of the composite increased rapidly with increasing confining pressure, though the elastic modulus remained constant. This suggests that the pressure effects were introduced by fracture processes. Microscopical examination of the kinked structures showed that the carbon fibres in the kink bands were broken into many fairly uniform short lengths. A model for kinking in the composite is suggested which involves the buckling and fracture of the carbon fibres.
Similar content being viewed by others
Abbreviations
- d :
-
diameter of fibre
- E f :
-
elastic modulus of fibre
- E m :
-
elastic modulus of epoxy
- G m :
-
shear modulus of epoxy
- k :
-
radius of gyration of fibre section
- l :
-
length of buckle in fibre
- P :
-
confining pressure (=σ 2 = σ 3)
- R :
-
radius of bent fibre
- V f :
-
volume fraction of fibres in composite
- ε t, ε c :
-
bending strains in fibres
- θ :
-
angle between the plane of fracture and σ 1
- σ 1 :
-
principal stress
- σ 3 :
-
confining pressure
- σ c :
-
strength of composite
- σ f :
-
strength of fibre in buckling mode
- σ n :
-
normal stress on a fracture plane
- σ m :
-
strength of epoxy matrix
- τ :
-
shear stress
- φ :
-
tangent slope of Mohr envelope
- ψ :
-
slope of pressure versus strength curves in Figs. 3 and 4.
References
B. W. Rosen, “Mechanics of Composite Strengthening”, A.S.M. Seminar, Phil. Pa. (October 1964).
Idem, Mech. Comp. Met. Proc. 5th Symp. Naval Structural Analysis (May 1967) p. 621.
Narmco R & D Div. Whittaker Corp., Contract AF 33 (615)-1660, AFML TR 65-237 (May 1965).
O. Orringer, ASOFR Sci. Rep., ASRL TR 162-1 (Oct. 1971).
H. C. Heard, J. Geology 71 (1963) 162.
M. S. Paterson, Int. J. Rock. Mech. Min. Sci. 7 (1970) 517.
M. V. Klassen-Neklyudova, M. A. Chernysheva and G. E. Tomilovskii, Sov. Phys. — Cryst. 5 (1961) 617.
E. M. De Ferran and B. Hornes, J. Comp. Mats. 4 (1970) 62.
E. Orowan, Nature 149 (1942) 643.
M. S. Paterson and L. E. Weiss, Geol. Soc. Amer. Bull. 77 (1966) 343.
L. E. Weiss, Proceedings of the Conference on Research in Tectonics, Ottawa 1968, Paper No. 68-32, edited by A. J. Baer and D. K. Morris (Geol. Survey Canada, 1969) p. 294.
J. B. Hess and C. S. Barrett, Trans. Met. Soc. AIME 185 (1949) 599.
L. R. Herrman, W. E. Mason and S. T. K. Chan, J. Comp. Mats. 1 (1967) 212.
Y. Lanair and Y. C. B. Fung, ibid 6 (1972) 387.
C. A. Berg and M. Salama, Fibre Sci. Tech. 6 (1973) 79.
C. W. Weaver and J. Williams, to be published.
J. R. Lager and R. R. June, J. Comp. Mats. 3 (1969) 48.
C. B. Raleigh and M. S. Paterson, J. Geophy. Res. 70 (1965) 3965.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Weaver, C.W., Williams, J.G. Deformation of a carbon-epoxy composite under hydrostatic pressure. J Mater Sci 10, 1323–1333 (1975). https://doi.org/10.1007/BF00540822
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00540822