Originally published December 1995
For the composite aircraft enthusiast and wood aircraft builder, there is an interesting new core material available (Core is the material which is sandwiched between wood or composite fiber laminations). This material, called Nida-Core H8PP Honeycomb, is a 4.8 Ib/cu ft polypropylene core. It is rot and corrosion-proof and is insensitive to styrene and most chemical agents.
The core material is currently used in the construction of at least one, cabin class, production boat hull. The material has natural sound dampening qualities and can be ordered in a fire-retardent variety.
What makes this material interesting to airplane builders is that the core is available in thicknesses from 5mm to 18 inches and is faced with a thermo-fused non-woven polyester scrim. The scrim facing makes it possible to wet layup and vacuum bag this honeycomb with an variety of resin systems including vinyl esters. The scrim also prevents the resin intrusion which would normally accompany any attempt to wet lay up typical honeycombs using conventional techniques. A wide range of adhesives, and skin materials can be bonded or laminated to this core including aluminum, formica, wood, steel, marble or glass. This material is a much better alternative to using balsa cores; and once thickness trades are considered, it is a possible substitute for several foams such as PVC and urethanes (in molded applications). The core also can also be ordered "scored" for laminations in compound curves. Once placed in such a compound curve, the scored volumes would be filled with an expanded foam or resin/filler slurry.
Several months ago, I came across an ad for this material in "High Tech Composites" magazine and subsequently filled out a reader service card. I recently received a box of sample material which sparked my imagination on possible applications. This is neat stuff. If you can't make it work in a fuselage surface core, it might work very well as a core for interior bulkheads. For infornation contact: Nida-Core Corporation, 65 Marshall & 111 Paterson, Hoboken NJ 07030, Phone 201-653-8181, Fax 201-653-1598.