Fiberglass Reinforced FRP Covered Plywood Panels for Trailers. Fiberglass reinforced plywood (FRP) covered panels are a type of composite material that is used in the production of trailers and other transportation vehicles. These panels are made by bonding a layer of fiberglass reinforced plastic (FRP) to the surface of a plywood panel, creating a strong, durable, and lightweight material that is ideal for use in the construction of trailers.