Abstract
Epoxy resins are toughened significantly by a dispersion of rubber precipitates. Microscopic examinations of propagating cracks in epoxy-rubber composites reveal that the brittle epoxy matrix cracks, leaving ligaments of rubber attached to the two crack surfaces. The rubber particles are stretched as the crack opens and fail by tearing at large, critical extensions. This fracture mechanism is the basis of a new analytical model for toughening. An increase in toughness (ΔG IC) of the composite is identified with the amount of elastic energy stored in the rubber during stretching which is dissipated irreversibly (e.g. as heat) when the particles fail. The model predicts the failure strain of the particles in terms of their size. It also relates the toughness increase to the volume fraction and tearing energy of the rubber particles. Direct measurements of the tearing strains of rubber particles, and toughness data obtained from epoxy-rubber composites, are in good agreement with the model. The particle-stretching model provides a quantitative explanation, in contribution to existing qualitative theories, for the toughening of epoxy-rubber composites.
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References
E. H. Merz, G. C. Claver and M. Baer, J. Polymer Sci. 22 (1956) 325.
L. E. Nielsen, “Mechanical Properties of Polymers” (Reinhold, New York, 1962).
J. A. Schmitt and H. Keskkula, J. Appl. Polymer Sci. 3 (1960) 132.
C. B. Bucknall and R. R. Smith, Polymer 6 (1965) 437.
S. Newman and S. Strella, J. Appl. Polymer Sci. 9 (1965) 2297.
C. B. Bucknall, “Toughened Plastics” (Applied Science, London, 1977).
C. B. Bucknall and T. Yoshii, Third International Conference on Deformation, Yield and Fracture of Polymers, PRI, Paper 13, Churchill College, Cambridge, April (1976).
F. J. McGarry, A. M. Willner and J. N. Sultan, Research Report R69-59, Massachusetts Institute of Technology (1969).
J. N. Sultan, R. C. Liable and F. J. McGarry, Appl. Polymer Symp. 16 (1971) 127.
R. Drake and A. Siebert, SAMPE Quart. 6 (1975).
S. C. Kunz, Ph.D. Thesis, University of Cambridge (1978).
A. R. Siebert and C. K. Riew, “The Chemistry of Rubber Toughened Epoxy Resins I”, 161st American Chemical Society Meeting, Organic Coatings Plastic Division, Los Angeles, March (1971) p. 552.
S. Visconti and R. H. Marchessault, Macromol. 7 (1974) 913.
L. R. G. Treloar, “The Physics of Rubber Elasticity” (Oxford University Press, London, 1949).
E. E. Underwood, “Quantitative Microscopy”, edited by R. T. DeHoff and F. N. Rhines (McGraw-Hill, New York, 1968) p. 149.
A. N. Gent, “Fracture”, Vol. 7, edited by H. Liebowitz (Academic Press, New York, 1972) p. 315.
R. S. Rivlin and A. G. Thomas, J. Polymer Sci. 10 (1953) 291.
H. W. Greensmith and A. G. Thomas, ibid. 18 (1955) 189.
H. M. James and E. Guth, J. Chem. Phys. 11 (1943) 455.
L. Mullins, Trans. Inst. Rubber Ind. 32 (1956) 231.
J. M. Scott and D. C. Phillips, J. Mater. Sci. 10 (1975) 551.
A. C. Meeks, Polymer 15 (1974) 675.
R. P. Kambour, J. Polymer Sci. Macromol. Rev. 7 (1973) 1.
W. D. Bascom, R. L. Cottingham, R. L. Jones and P. Peyser, J. Appl. Polymer Sci. 19 (1975) 2545.
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Kunz-Douglass, S., Beaumont, P.W.R. & Ashby, M.F. A model for the toughness of epoxy-rubber particulate composites. J Mater Sci 15, 1109–1123 (1980). https://doi.org/10.1007/BF00551799
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DOI: https://doi.org/10.1007/BF00551799