There are products that can be cut into strips and used in place of wood but it is not a one for one substitution. Because wood has ample stiffness the number of mold frames is not great. If you use something less stiff the number has to be increased so the the non-wood strips do not sag between molds.
The glass/wood composit hasn't been around for all that long but it's likely that everything that could possibly replace wood has been tried by now and wood is still number 1.
Foam core panels for marine use can be substituted for plywood in many designs but the cost is about double because more glass and epoxy is needed to achieve the resistance to penetration that is inherent in plywood. And, the increase in epoxy means light weight goes out the window.

: I guess wood has a lot going for it and I'm sure this is another question
: discussed in the past but...

: Plywood seems to be stronger than "natural" wood against direct
: impacts due to the plys, and I guess foam cores have also been used
: (surfboard construction is going thru a phase now since the foam is not
: environmentally friendly) but has anyone used some type of plastic strips
: to strip build a kayak? Most people seem to go on "expeditions"
: with a plastic kayak maybe for greater peace of mind.

: Maybe thick, sort of stiff, rubber instead of wood as a core, with something
: other than epoxy? And is there nothing other than varnish or paint to
: provide uv protection? Polyurethanes are cheaper but sound not as user
: friendly overall. Spreadable, cheap, silicon rubber would be nice. Wood
: looks nice and all but...