New Boeing 787 Composite Construction

Use of any metal alloys and welding in aircraft construction proved that welding did not prevent crack propagation but riveting did. Mechanical properties of composites are such that there is no uniform crystaline structrure so crack propagation in classical sense is not a problem, where is the amazing part?

Sailplanes have been using it for 30 years, not amazing just slow to new processes, What is amazing is now the no small company can buy carbon fiber as boeing and airbus are buying it all up.

The amazing part is that this type of composite construction came from advances in sail making design and production by North Sails in their 3DL shop. From making sails that conformed to a computerized design shape, they continued to turn out their material in a roll or cylindrical shape that became a fuselage.

I'd be interested in knowing how Boeing plans to deal with surface finish. In sails, we are used to visible seams, stitching, etc. so a 3DL sail looks pretty smooth by comparison. But we are accustomed to seeing very sooth surfaces on aircraft (at least on recent aircraft). Most composite parts have been laid up in female molds so the rough side is inside, where it is not seen. On a male mold, the rough side is outside. I wonder if they will fair the surface or leave it as laid up?

Actually, the technology comes from the military. The hold up for Boeing has been ITAR. Because this aircraft is being sold outside of the US the ITAR regulations created a storm that has finally been settled between Boeing and the US government.

You would have seen this a long time ago if ITAR was not an issue.

Although I commend the exploration into using new materials and such, I have one big problem to bring up with these new materials: recyclability.

Aluminum and steel parts can be salvaged...all the carbon fiber and resins going into new planes can never be used again. Some resins can be reflowed but this does not really mean reused. If anybody thinks that aircraft graveyards look wasteful now, wait until 20 years from now.

I get the impression that many composite constructions methods being used now are what styrofoam was when it was discovered...the next great thing with a lot of environmental/disposal problems that came up later and ultimately where the reason companies quit using them.

Unlike many I do not know what 'Composite' is. Can anybody throw some light?

CARBON FIBER IS A FORM OF GRAPHITE. IT'S USED TO REINFORCE MATERIAL LIKE EPOXY RESINS AND OTHER THERMOSETTING MATERIAL. THERE CALLED COMPOSITES BECAUSE THEY HAVE MORE THAN ONE COMPONENT. CARBON FIBER IS MADE FROM A POLYMER CALLED POLYACRYLONITRILE; BY A COMPLICATED HEATING PROCESS WERE RIBBONS OF GRAPHITE PACK TOGETHER TO FORM FIBER. IT'S USED IN PLACE OF METAL IN THE SPACE SHUTTLE, AIRPLANES, RACE CARS AND ANYWHERE METAL CAN BE USED.

Bransons answer is good. Other composites include glass fiber in polyester, vinylester, and epoxy resins... Kevlar fibers in similar resins, etc. There are also thermoplastic composites, in which the plastic portion melts when warmed and solidifies as it cools.

There is usually a strong synergistic effect in composites: A piece of carbon cloth is just a piece of cloth: soft, flexible, and not something you'd think you could make an airplane out of. The resin, on the other hand can be fairly rigid, but is weak. But together, Woo Hoo! The resulting material is extremely strong, stiff and light. The resin is strong enough to keep the fibers from wiggling around and buckling, so the composite has both high compressive and tensile strengths. (Without the resin the compressive strength would be be essentialy non-existent.) At the low tech end of the composite world are the things we usually just call fiberglass: Corvettes, boats, etc.

Low tech fiberglass...like the lightweight, highspeed incredibly tough aircraft going together in so many garages? I'll grant it didn't have to be autoclaved, but low tech?

Actually the delay getting composites on large aircraft was testing their "goodness." I was involved with a firm that put a weight saving rudder on a business jet. By the time we finished inserting reinforcing steel in the design to satisfy the FAA that it wouldn't seperate from the aircraft no matter the failure, it weighed more than the aluminum one it replaced.

Composites are very difficult to test for quality as it is the Process you have to test; the Product, good or bad, initially the Product can look the same. Almost to the point of failure. Drove our Non-Destructive Test guys nuts.

Then there is the whole question of repair, not trivial. How many pointwise failures can you have, of what size, before the hull is compromised? I would love to see the failure analysis! And the continued airworthiness instructions. And field repair! Try telling the difference between good fiberglass repair and bad Bondo on your Corvette. Now fly in it.

I personally look forward to the day we can manipulate carbon molocules at the nano level to weave a hull. Then I can reuse whatever nanomethod I used to make the hull, to repair the hull.

Emmett

I meant relatively low tech, as compared to carbon fiber, which itself has been around for quite a while: it is, after all, the stuff that even relatively cheap tennis rackets have been made of for many years. Actually, re homebuilt aircraft, wood works extremely well. Using it, you can construct a wing that is lighter and stronger than the foam-cored fiberglassed skinned wings of a Vari Eze. (Burt Rutan is the first to admit that the wings on the Vari Eze were not weight-efficient, albeit cool for other reasons.) (Matching a Lancair wing, or the wing of a sophisticated sailplane with wood would be harder.)

Re certification: the best you can hope for is that when the paperwork equals the weight of the plane, you're ready for certification. And that assumes conventional aluminum construction. Perish the thought that you should try anything new.

Re nano: me too! I think that day is not toooooo far off: at least to the extent of being able to demonstrate it on a small scale.

I had this idea for being in two places at once: 3D printers already exist. Use amino acids instead of plastics.