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.
A new compression molding compound material combines the light weight, strength, and rigidity of carbon fibers with the flexibility and lower cost of glass materials in a composite compatible with automotive production.
Plastic bearings are real and millions of them are in use doing heavy-duty jobs we used to think only metals could do. Some of Germany-based igus's bearings are traveling around the world as functional parts in a car to demonstrate what they can do.
Baxter showed off his 2.0-derived moves at ATX West this year. The big red guy still looks pretty much the same, but has some new abilities, mostly due to software. The research robot version is now being used in corporate R&D departments as a design platform.
End-production using 3D printing, including objects made of multiple materials in one pass, is getting closer to reality as we saw on the exhibit floor at the recent Pacific Design & Manufacturing Show.