fiber pull-out

{{Short description|One of the failure mechanisms in fiber-reinforced composite materials}}

{{Use American English|date=March 2021}}

{{Use mdy dates|date=March 2021}}

Fiber pull-out is one of the failure mechanisms in fiber-reinforced composite materials.{{cite journal | author=WJ Cantwell, J Morton | title=The impact resistance of composite materials -- a review | journal=Composites | year=1991 | volume=22 | issue=5 | pages=347–62 | doi=10.1016/0010-4361(91)90549-V}} 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.Serope Kalpakjian, Steven R Schmid. "Manufacturing Engineering and Technology". 6th Ed. Prentice Hall, Inc. 2009, p. 223. {{ISBN|0136081681}}

Work for debonding, $W\_d\; =\; \backslash frac\{\backslash pi\backslash ;\; d^2\backslash ;\; \backslash sigma\_f^2\backslash ;\; l\_d\}\{24\backslash ;\; E\_f\}$ PWR Beaumont. "[https://doi.org/10.1016/b978-0-08-024766-3.50012-4 Fracture mechanisms in fibrous composites]". Fracture Mechanics, Current Status, Future Prospects. Edited by RA Smith. Pergamon Press: 1979. p211-33 in {{cite journal | author=WJ Cantwell, J Morton | title=The impact resistance of composite materials -- a review | journal=Composites | year=1991 | volume=22 | issue=5 | pages=347–62 | doi=10.1016/0010-4361(91)90549-V}}

where

• $d$ is fiber diameter
• $\backslash sigma\_f^2$ is failure strength of the fiber
• $l\_d$ is the length of the debonded zone
• $E\_f$ is fiber modulus

thumbIn ceramic matrix composite material this mechanism is not a failure mechanism, but essential for its fracture toughness,V. Bheemreddy et al. "[http://www.sciencedirect.com/science/article/pii/S0927025613004278 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. 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.W. Krenkel, ed.:Ceramic Matrix Composites, Wiley-VCH, Weinheim, 2008, {{doi|10.1002/9783527622412}} {{ISBN|978-3-527-31361-7}}{{pn|date=January 2024}} 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.