Why do helicopter rotor blades use rigid PMI foam?

Rigid PMI foam is widely used in helicopter composite rotor blades. Using PMI foam as the blade core material can greatly extend the service life of the rotor. PMI foam can also support the blade skin profile and provide partial torsional stiffness to the blade profile.

The molding process is often used to mold composite blades. By designing the interference amount of PMI foam, it is ensured that during the molding process of composite blades, the PMI foam can provide sufficient back pressure to ensure the surface quality of the blade.