Almost all of the weight savings is certainly lost with the addition of fillers. If the ribs, bulkheads, webs, etc., are attached or reinforced with a wet lay-up process, graphite fabric and epoxy must be used and, again, a good visual inspection will be impossible. Honeycomb will permit water to accumulate in the core area, causing further corrosion. If the water freezes, it will separate the skin. Dry graphite fabric must be handled with more care than fiberglass.
Fibers can break and loose particles can be inhaled.
Also, cured carbon splinters will not work their way out of the skin as would glass or wood. He points out that porous prepregs must be fuel proofed, coated with acceptable sealants or Derakane 411, or they will leak fuel. For corrosion resistance, of course, vinyl esters are the choice of the chemical industry. He stated that he has learned from experience that a wet lay-up of graphite does not make sense because the coarse weave has a high resin content and is so heavy that the advantages of the lighter and stronger graphite are not realized or offset by its higher cost. The bottom line for graphite vs fiberglass is cost.