Dependence of Crack Propagation/Deflection Mechanism on Characteristics of Fiber Coating or Interphase in Ceramics Matrix Continuous Fiber Reinforced Composites (Postprint)
Interim rept. 22 Jul 2013-22 Jun 2014
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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Toughness in continuous ceramic fiber reinforced ceramic matrix composites CMCs with dense matrices are dependent on the properties of the fiber coating or interphase that separate the fibers from the matrix. Multiple criteria have been proposed to describe the mechanism of crack propagationdeflection at the filament scale in brittle matrix continuous fiber reinforced composites however, most of these criteria fail to account for the presence of an interphase of finite thickness or employ unrealistic boundary conditions. Recent simulations employing the extended finite element method XFEM have shown that variations in interphase thickness and strength relative to the fibersmatrix can have a significant influence on the mechanism of crack propagationdeflection. It is shown that primary crack deflection most often occurs when conditions favor secondary cracking in the interphase in front of an approaching matrix crack. Although this mechanism is similar to that argued by Cook and Gordon Cook J, Gordon JE, Proc. Roy. Soc. A 1964 28 508-520, variations in the properties of the interphase are simulated to produce large deviations in the local crack growth behavior as a matrix crack grows into interphase.
- Laminates and Composite Materials