a ceramic-matrix composite
Ceramics survive ferocious heat but shatter like glass. A ceramic-matrix composite embeds ceramic fibers (often silicon carbide or carbon) in a ceramic matrix specifically to add toughness, to turn a brittle material into one that cracks gracefully instead of exploding.
The trick is a deliberately weak fiber-matrix interface. When a crack runs through the brittle matrix and hits a fiber, instead of slicing through, the crack is deflected along the weak interface; the fiber then bridges the crack and pulls out, soaking up energy. This raises fracture toughness several-fold (from about 3 to 5 up into the 15 to 30 MPa times sqrt(m) range) even though every ingredient is brittle. Note this is the opposite design goal from most composites, where you want a strong bond.
CMCs let engines run hotter and lighter than superalloys allow: SiC/SiC turbine shrouds and combustor liners, carbon-carbon rocket nozzles, Space Shuttle nose caps, and brake discs. They are extremely expensive, slow to make, and still far more brittle than metals, but they can work above 1200 to 1500 degrees C where metals melt or oxidise.
Carbon-carbon (carbon fibers in a carbon matrix) forms the leading edges of re-entry vehicles and Formula-1 brake discs: it keeps its strength when glowing hot, where metal would soften.
Toughening a brittle ceramic by letting cracks deflect and fibers pull out.
In a CMC you want a WEAK interface, the opposite of most composites, because the crack-deflecting, fiber-pull-out toughening only works if the crack can debond and slide along the fiber. A strong bond would let the crack cut straight through and stay brittle.