Alligatoring- A cosmetic defect in the gel coat layer. It looks like a wrinkled surface which resembles alligator skin. This is often caused by the gel coat being applied too thin. It can also be caused by not allowing the gel coat to cure long enough before adding subsequent layers.
Orange peel- A pebbly texture on the cured gel coat similar to an orange peel. It is caused by PVA (mold release film) if the gel coat is sprayed onto a mold. It can also be caused by spraying gel coat onto the outside of the part. Gel coat is thicker than paint and does not lay down as smooth. This texture on the finished product will need to be polished for a better cosmetic look.
Chopped strand mat– A mat formed of strands cut to a short length, randomly distributed, without intentional orientation, and held together by a resin binder. The binder is dissolved when resin is applied. Chopped strand mat is not compatible with epoxy resin.
FRP- Fiber reinforced plastic also known as GFRP (Glass Fiber Reinforced Plastic). It is a general term for a resin/fiber composite.
Unidirectional- Most of the fibers are oriented in the same direction. This makes the majority of the strength in one direction.
Microspheres- 3M’s brand name for this is 3M glass bubbles. They are small, hollow glass spheres used as fillers in epoxy and polyester compounds to reduce density. This filler is lightweight and easy to sand. It can be used on minor surface repairs. It makes a good putty for cracks and holes when mixed with resins.
Tooling- The molds and fixtures used to produce a composite article (fibers and resin). Tooling may be made with any suitable material but composites are a popular choice.