Mechanics of Composite Materials

, Volume 17, Issue 3, pp 276–280 | Cite as

Model of a macrocrack in a composite

  • S. T. Mileiko
  • F. Kh. Suleimanov
Article
  • 19 Downloads

Conclusions

  1. 1.

    The dependence of the crack resistance K* of a composite on the volume fiber content Vf may both be monotonically decreasing (x=26 in Fig. 5a) and have a maximum at a certain volume fiber fraction (x=10, x=8 in Fig. 5a). Within the framework of our model, it is possible to have an indefinitely increasing K* at sufficiently small x — this corresponds to a material insensitive to a crack of a certain size. Qualitatively, this behavior of the model is consistent with experiment: in [5] K* for boroaluminum (x small) increases with increase in Vf, in [7] the K* for a tungsten-copper composite (x large) falls with increase in Vf.

     
  2. 2.

    As the crack length increases, K* tends to a constant value which can be taken to be characteristic of a given structure (see Fig. 5b). However, the necessary crack length may be too great for the performing of the corresponding experiment.

     
  3. 3.

    The fracture toughness of the matrix has a very important influence on crack resistance (see Fig. 5c). If we regard the composite structure as amplifying the crack resistance of the matrix, then the amplification is nonlinear.

     
  4. 4.

    The crack resistance of the composite depends importantly on the fiber characteristics on a length of the order of the critical length (mean distance between fiber defects failing in a given test).

     
  5. 5.

    The fact that the crack resistance of the composite structure depends on a large number of factors both opens up broad possibilities of controlling the crack resistance of composites and, at the same time, leads to considerable scatter of the experimental data.

     

Keywords

Experimental Data Fracture Toughness Crack Length Composite Structure Important Influence 

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Literature cited

  1. 1.
    J. Cook and J. E. Gordon, “A mechanism for the control of crack propagation in an allbrittle system,” Proc. R. Soc.,A-282, No. 1391, 508 (1964).Google Scholar
  2. 2.
    Yu. N. Rabotnov and A. N. Polilov, “Strength criteria for fiber-reinforced plastic,” in: Composite Materials, Moscow (1979), pp. 375–384.Google Scholar
  3. 3.
    S. T. Mileiko, “Micro- and macrocracks in composites,” Mekh. Kompozitn. Mater., No. 2, 276–279 (1979).Google Scholar
  4. 4.
    A. Kelly, “Interface effects and the work of fracture of a fibrous composite,” Proc. R. Soc.,A-319, No. 1536, 95–116 (1970).Google Scholar
  5. 5.
    S. T. Mileiko, N. M. Sorokin, and A. M. Tsirlin, “Crack propagation in a boroaluminum composite,” Mekh. Kompozitn. Mater., No. 6, 1010–1017 (1976).Google Scholar
  6. 6.
    S. T. Mileiko and V. I. Kaz'min, “Strength of sapphire fibers and sapphire-molybdenum composites,” Mekh. Kompozitn. Mater., No. 4, 723–726 (1979).Google Scholar
  7. 7.
    G. A. Cooper and A. Kelly, “Tensile properties of fiber-reinforced metals: fracture mechanics,” J. Mech. Phys. Solids,15, No. 4, 279 (1967).Google Scholar

Copyright information

© Plenum Publishing Corporation 1981

Authors and Affiliations

  • S. T. Mileiko
    • 1
  • F. Kh. Suleimanov
    • 1
  1. 1.Institute of Solid-State PhysicsAcademy of Sciences of the USSRMoscow

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