FRP is fiber reinforced plastic.
Use of any type of of FRP in the structure of the aircraft is prohibited. Examples of prohibited FRP that cannot be used in the construction of a Regular class aircraft include, but are not limited to:
Pultruded pre-shaped carbon rods, tubes, and other shapes.
Rule 7.2.1 does have some exceptions for commercially available FRP parts that are allowed. Teams are not allowed to create or manufacture any of these FRP parts mentioned in the exceptions. These parts can only be purchased. Teams may modify these allowed parts by cutting, drilling or sanding. Teams are not allowed to add new FRP material to the commercially available parts.
For more details about what constitutes FRP, please consult Wikipedia at the link below: