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Fiber‐reinforced ceramic composites achieve high toughness through distributed damage mechanisms. These mechanisms are dependent on matrix cracks deflecting into fiber/matrix interfacial debonding cracks. Oxidation resistance of the fiber coatings often used to enable crack deflection is an important limitation for long‐term use in many applications. Research on alternative, mostly oxide, coatings for oxide and non‐oxide composites is reviewed. Processing issues, such as fiber coatings and fiber strength degradation, are discussed. Mechanics work related to design of crack deflecting coatings is also reviewed, and implications on the design of coatings and of composite systems using alternative coatings are discussed. Potential topics for further research are identified.

The fiber pullout and pushout tests have been analyzed to predict the load‐displacement behavior in terms of fiber/matrix interface parameters. The effects of residual axial strain in the fiber and fiber surface topography were included. The residual axial strain was found to be a significant parameter. It is shown that the interface failure can be progressive or catastrophic. In the case of a progressive failure of the interface, the load‐displacement curve is nonlinear. The portion of the curve from above the first nonlinearity to near the peak load can be predicted in terms of parameters of the interface, viz., the friction coefficient, the radial stress at the interface, the fracture toughness of the interface, and the residual axial strain in the fiber. Values for these parameters can be obtained from a single loaddeflection curve. The peak load and load drop, which are usually reported, are found not to be directly relatable to any interface property, since the length of the last portion of the fiber to debond is influenced by end effects and hence not easily predicted. However, for data which describe the peak load as a function of initial embedded length, that factor can be eliminated and the data reduced to yield the relevant interface parameters. In pullout, the peak and friction loads saturate with large specimen thickness. Catastrophic failure is favored when the debond initiation load is high or when residual stress is low. Finally, a methodology to extract interface parameters from experimental data is suggested.

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Experimental data on the oxidation kinetics of SiC‐containing diborides of Zr and Hf in the temperature regime of 1473–2273 K are interpreted using a mechanistic model. The model encompasses counter‐current gas diffusion in the internal SiC depleted zone, oxygen permeation through borosilicate glass channels in the oxide scale, and boundary layer evaporation at the surface. The model uses available viscosity, thermodynamic and kinetic data for boria, silica, and borosilicate glasses, and a logarithmic mean approximation for compositional variations. The internal depletion region of SiC is modeled with CO/CO2 counter diffusion as the oxygen transport mechanism. Data reported for pure SiC in air/oxygen, for ZrB2 containing varying volume fractions of SiC, and for SiC–HfB2 ultra‐high temperature ceramics (UHTCs) by different investigations were compared with quantitative predictions of the model. The model is found to provide good correspondence with laboratory‐furnace‐based experimental data for weight gain, scale thicknesses, and depletion layer thicknesses. Experimental data obtained from arc‐jet tests at high enthalpies are found to fall well outside the model predictions, whereas lower enthalpy data were closer to model predictions, suggesting a transition in mechanism in the arc‐jet environment.