Jet engines are lined with kevlar to contain engine failures. It usually works. Uncontained engine failures are extremely rare. I'd hope they are using similar

Jet engines are lined with kevlar to contain engine failures. It usually works. Uncontained engine failures are extremely rare. I'd hope they are using similar technology to prevent flywheel bits from flying outside the bus. Parts around the flywheel container will probably be damaged or destroyed but the container should survive intact. There's two types of flywheels I'm aware of that are failsafe. The first is a tape flywheel. On failure it unwinds inside the container. The other type is a system where the disk is made of powdered ceramic. In the event of overload it turns to dust. A paper I found online suggests the F1 system uses a powdered ceramic disk: http://136.142.82.187/eng12/Author/data/2097.docx http://136.142.82.187/eng12/Author/data/2097.docx