1) Composite material 
Gelcoat is a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite material. The most common gelcoats are based on epoxy or unsaturated polyester resin chemistry. Gelcoats are modified resins which are applied to moulds in the liquid state. They are cured to form crosslinked polymers and are subseque...
a protective layer of resin on fibreglass
A colored, polyester resin material used to form the surface of some fiberglass bathubs or showers. Don't confuse with acrylic on fiberglass.
a thin layer of unreinforced resin on the outer surface of a reinforced resin moulding; it hides the fibre pattern of the reinforcement, protects the resin/reinforcement bond, gives smooth external finish and can also provide special properties; it is usually pigmented