Alcoa's Keensert inserts and studs, shown here, along with Inconel 718 bolts and standard hexagon nuts, went to Mars on the Curiosity Rover. In spacecraft and aircraft, Keenserts provide high resistance to torque-out and pullout loads.
The lightning strike issue isn't about frequency so much as it is about catastrophic results. If you've only got a (for example) 1% chance of something happening, but that something has catastrophic results--people dying, lawsuits--then that's something you've got to protect against, or at least not encourage, in your materials and assembly process selection.
I never thought that lightening strikes on aircraft was so common. I read that it happens 2 times per year on average, per airplane. I have seen electrical discharge responsible for fastener loosening and in some cases, ejecting.
There is a downside to composite pieces, price. Bolting parts together will always be around. I designed a mechanical system that ended up having over 60 bolts.. it was cheaper than with none, that was for sure.
Glad you liked the article. The whole issue of the grounding of composites used in aircraft has been widely misunderstood, so I thought it was a good idea to include some clear discussion on that issue. Could you clarify your question about comparisons between fasteners for composites and fasteners for metal? What sort of comparisons do you have in mind?
Excellent post Ann. I know the longevity of any fastener is dependent upon the application and use. Relative to composite fasteners, do we know how they "stack up" relative to metal fasteners? I have seen no data that tries to correlate life cycles of either type. Great point also about the grounding of composites. I know this must be a huge issue but not talked about too much in the literature.
That's true of course. The question is, given an increase in composite use, whether fasteners will be used in high enough quantities in repair to make up for the lower overall quantities in manufacturing.
To give engineers a better idea of the range of resins and polymers available as alternatives to other materials, this Technology Roundup presents several articles on engineering plastics that can do the job.
The first photos made with a 3D-printed telescope are here and they're not as fuzzy as you might expect. A team from the University of Sheffield beat NASA to the goal. The photos of the Moon were made with a reflecting telescope that cost the research team £100 to make (about $161 US).
A tiny humanoid robot has safely piloted a small plane all the way from cold start to takeoff, landing and coming to a full stop on the plane's designated runway. Yes, it happened in a pilot training simulation -- but the research team isn't far away from doing it in the real world.
Some in the US have welcomed 3D printing for boosting local economies and bringing some offshored manufacturing back onshore. Meanwhile, China is wielding its power of numbers, and its very different relationships between government, education, and industry, to kickstart a homegrown industry.
You can find out practically everything you need to know about engineering plastics as alternatives to other materials at the 2014 IAPD Plastics Expo. Admission is free for engineers, designers, specifiers, and OEMs, as well as students and faculty.
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