The main problem seems to be where composites interface with metals: and that is a new problem. It happens because a commercial plane is made of both materials: composites have not been designed to replace everything yet and metal can't be used everywhere due to weight/fuel reduction requirements. These problems took about 10 years to show up in in-service planes.
I would expect that these type of problems of material incompatibility would be first tested and then applied on smalled jet designs. The stress may be better detected at faster speeds and fuselage deformations under changing Gs.The chance of serious accident with many lives lost is a clear possibility. I would avoid this plane as a plague for now.
naperlou, I think the potential gap between existing modeling techniques and assumptions and the new realities of a new material is a good point, and one that the GAO was concerned about in its report addressing repairs to the Boeing 787's composites: http://www.designnews.com/document.asp?doc_id=235037 They focused on the back end of repair and maintenance, not the front end of design, but the concerns were similar.
The fastener problem makes me, too, wonder about safety issues, regardless of what Airbus says. In a previous feature on fasteners, manufacturers told me they were designing new ones to go into new composite materials, which have very different requirements from metal. So what does that say about whatever fasteners or insertion techniques are currently being used? OTOH, composites in aircraft are not at all new and you'd think they'd have figured out that part by now.
Beth, I agree with you. I wouldn't fly one yet. If they really could tell if it was safe they would not have had the problem. This is new stuff. They can't really know.
I saw a similar situation on the Landsat spacecraft. The structure was a large space frame made of composite tubes. The joints were of metal (titanium, I think). It was clear that if you put the fastrner holes in the normal position, as for an all metal structure, that there would be problems with cracks. This was becuase of the use of dissimilar materials. This was found by building a test sub-structure. I wonder if Airbus did enough testing of actual materials, or whether they relied on CAE. When using new materials it is important to understand that the CAE tools may not be able correctly predict what is happening.
Some how knowing there are cracks in the wings and knowing they aren't on track to be fully fixed until 2013 would make me very reticient to hop on one these babies, even though they are undoubtedly a beautiful example of A&D design.
Interesting that Airbus has suffered its fair share of setbacks on this plane, due mostly to miscommunications and missteps in the design process. To whit: One of the highly publicized delays related to the project was due to problems around the wiring harness system and the structural design--a miscue some attributed to interoperability and incompatibility issues between CAD platforms.
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This is part one of an article discussing the University of Washington’s nationally ranked FSAE electric car (eCar) and combustible car (cCar). Stay tuned for part two, tomorrow, which will discuss the four unique PCBs used in both the eCar and cCars.
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