Did you mean epoxy? I've not heard the term expoxy before.

Some sailplanes have their wings constructed with foam, fiberglass and epoxy. The glass is laid down at a reasonable thickness (at least 1/64") which provides a lot of strength and stiffness to the foam. Except it is quite heavy which isn't too much of a problem in sailplanes.

Sport planes usually have a light component (sheet wood, cardboard) directly on the foam first, before the epoxy glass is applied usually in a much thinner and much lighter section..