Fiber pull-out

Fiber pull-out is one of the failure mechanisms in fiber-reinforced composite materials.[1] Other forms of failure include delamination, intralaminar matrix cracking, longitudinal matrix splitting, fiber/matrix debonding, and fiber fracture.[1] The cause of fiber pull-out and delamination is weak bonding.[2]

Work for debonding, [3]

where

  • is fiber diameter
  • is failure strength of the fiber
  • is the length of the debonded zone
  • is fiber modulus

In ceramic matrix composite material this mechanism is not a failure mechanism, but essential for its fracture toughness,[4] which is several factors above that of conventional ceramics.

The figure is an example of how a fracture surface of this material looks like. The strong fibers form bridges over the cracks before they fail at elongations around 0.7%, and thus prevent brittle rupture of the material at 0.05%, especially under thermal shock conditions.[5] This allows using this type of ceramics for heat shields applied for the re-entry of space vehicles, for disk brakes and slide bearing components.

References
  1. WJ Cantwell, J Morton (1991). "The impact resistance of composite materials -- a review". Composites. 22 (5): 347–62. doi:10.1016/0010-4361(91)90549-V.
  2. Serope Kalpakjian, Steven R Schmid. "Manufacturing Engineering and Technology". International edition. 4th Ed. Prentice Hall, Inc. 2001. ISBN 0-13-017440-8
  3. PWR Beaumont. "Fracture mechanisms in fibrous composites". Fracture Mechanics, Current Status, Future Prospects. Edited by RA Smith. Pergamon Press: 1979. p211-33 in WJ Cantwell, J Morton (1991). "The impact resistance of composite materials -- a review". Composites. 22 (5): 347–62. doi:10.1016/0010-4361(91)90549-V.
  4. V. Bheemreddy et al. "Modeling of fiber pull-out in continuous fiber reinforced ceramic composites using finite element method and artificial neural networks," Computational Materials Science, Vol. 79, pp.663-676, 2013.
  5. W. Krenkel, ed.:Ceramic Matrix Composites, Wiley-VCH, Weinheim, 2008, ISBN 978-3-527-31361-7
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