Failure tolerant functionally graded fiber-reinforced UHTCs exposed to hypersonic flows

A functionally graded ZrB2 ceramic containing increasing content of short carbon fiber, 0–60 vol%, was tested in a supersonic arc-jet wind tunnel by exposure to flow in simulated air. The composite, that exhibited increased failure tolerance due to the combined toughening effect of the fiber bridging and the residual stresses accumulated between scales of different composition, successfully survived 2120 K for 300 sec, whereas scale spalling occurred upon reaching 2930 K. Overall, in both conditions, carbon fiber remained protected and with unchanged morphology, providing the necessary structural stability for surviving the shocks encountered by the hottest components of new generation aerospace vehicles.