The Boeing B787 Dreamliner : The plastic aeroplane that might break a few dreams?
If as a kid, you made plastic model aircraft, then your mother came along with a duster and sent it crashing to the floor in bits. Here is an analogy...
Boeing's B787 Dreamliner. It looks like the offspring between a Boeing B767 and a B777. Another boring tube with two engines.
That is where the similarity ends. It was hoped that the radical use of composite materials, put more simply, plastic. Would enhance its performance over other aircraft. These materials are already in use in airliners. Parts of the wing, the tailplane etc, but not to the extent of the Boeing 787. The aircraft will be lighter and therefore more fuel efficient. Add this to more efficent engines and in theory, the B787 Dreamliner should leave the opposition behind. It even has the novel idea of windows that darken like light recting sunglasses. No shutters for the windows, thereby saving even more weight. A very efficient aeroplane.
But, it is two years late, why ?
There are problems with the composite materials. One problem that has not been mentioned is the way the material cracks. Aircraft are occasionally hit by ground vehicles, driven by careless drivers. No problem say Boeing, just glue in a new section to replace the damaged area. At the moment, most composites are used in areas that are not prone to ground damage. The tail section for instance. A crack could run the complete length of the fuselage, not being visible. Have Boeing thought about this ?
There is trouble with the wing box, where the wings join the fuselage:-
"A former employee of Boeing who has been laid off last year claims that the new carbon-composite airframe of the upcoming Boeing 787 Dreamliner may be unsafe. According to ATW News, Vince Weldon who had worked for Boeing for 46 years claims in an interview with journalist Dan Rather that he was fired in 2006 because he pointed out safety glitches in relation to this new breakthrough technology to be used widely in the construction of the Dreamliner (composite is to replace aluminium in the bodyframe of the airliner).
The new Dreamliner – which was revealed a little more than two months ago - is to have a body fully built from composite materials, which guarantee weight reduction (thus increased fuel efficiency and less environmental harm), as well as the possibility of more humidity in the passenger cabin, which would reduce the effects of flying on the human body. At the time when he was laid off, he was working for the Phantom Works technology centre of Boeing, developing the new composite plastic materials for the new aircraft. Boeing officially claims they had to fire him as he had assaulted his bosses several times.
I don’t think Engineers always understand the materials they are dealing with in the detail required. Composites, if treated like black metals instead of understanding the importance of fibre, resin and interface properties can give trouble.
Boeing 787 wing flaw extends inside plane
The wing damage that grounded Boeing's new composite 787 Dreamliner occurred under less stress than previously reported — and is more extensive.
An engineer familiar with the details said the damage happened when the stress on the wings was well below the load the wings must bear to be federally certified to carry passengers.
In addition, information obtained independently and confirmed by a second engineer familiar with the problem shows the damage occurred on both sides of the wing-body join — that is, on the outer wing as well as inside the fuselage.
The structural flaw in the Boeing design was found in May during a ground test that bent the wings upward. Stresses at the ends of the long rods that stiffen the upper wing skin panels caused the fibrous layers of the composite plastic material to delaminate.
The damage at the end of each of the 17 long stiffening rods, called stringers, on each wing's upper skin happened just beyond the aircraft's "limit load," which is the maximum load the wing is expected to bear in service.
|ÇÑ¹·Õè ¨Ñ¹·Ãì ¡Ñ¹ÂÒÂ¹ 2552|