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The micromechanics of fatigue-induced delamination of a graphite/epoxy composite

Abstract

Fatigue crack growth in the resin layer between 0 and 90 plies of an AS/3501-5A graphite fibre/epoxy composite is discontinuous. Regularly spaced extensions of the crack front occur after periods of arrest. Crack compliance and tip strain fields have been measured to determine how the local minimum (K min l) and maximum (K max l) crack tip stress intensities affect growth. Contact of the fracture surfaces and swelling of the 90° ply modify these local stress intensities by an amount sensitive to load ratio (R), and the resulting propagation rate depends strongly onR. A model capable of describing thisR effect relates the distance of each individual crack advance to Kmax l and the duration of each arrest toK mnax l -K min l, i.e., to ΔK eff. We discuss the genesis of this model, and its explanation of the large Paris law coefficient which results if growth rates are instead expressed against the applied cyclic stress intensity.

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Morris, W.L., Zurek, A.K. The micromechanics of fatigue-induced delamination of a graphite/epoxy composite. J Mater Sci 22, 4426–4433 (1987). https://doi.org/10.1007/BF01132042

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Keywords

  • Fatigue
  • Graphite
  • Fracture Surface
  • Stress Intensity
  • Fatigue Crack