Fiber pull-out is one of the failure mechanisms in fiber-reinforced composite materials. Other forms of failure include delamination, intralaminar matrix cracking, longitudinal matrix splitting, fiber/matrix debonding, and fiber fracture. The cause of fiber pull-out and delamination is weak bonding.
Work for debonding,
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, which is several factors above that of conventional ceramics.
The figure is an example for 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. 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.
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