Exotic Frame Materials

[cgates66]

Is anyone familiar with the use of newer metal matrix composites for frames? Two that spring to the eye are aluminum / carbon fiber (as opposed to epoxy / carbon fiber) and apparently titanium silicon carbide has decent mechanical properties as well.

The carbon / epoxy stuff can be built into a great frame because its strength is highly directional - but as everyone knows, the price for that is durability and resistance to "non-designed" loads. Nevertheless, some amount of directionality in cycling is highly desirable (torsional and lateral rigidity vs. vertical for example).

It looks like there are some emergent materials that might exhibit some of the directional behavior of carbon fiber, by using a metal as the "matrix" instead of epoxy, which might be a best-of-both-worlds situation (at a high cost in $$$).

I haven't really turned anything up other than the old Specialized stuff which I think was aluminum-based and I believe still isotropic, but with significantly better strength and rigidity than a traditional aluminum alloy.

[Buzz]

http://hollandcycles.com/holland-exogrid/

Not sure if this is what you are thinking about. Saw one in person once and it was pretty cool and “exotic” looking.

[cgates66]

Qualitatively, yes; quantitatively not exactly - but that is a very interesting bicycle which I am going to look at.

If you think of carbon/epoxy, there are long threads of carbon bound together by an epoxy resin. The fibers are something like 60% of the total volume. I've read about using aluminum as the "resin", which adds significantly to the strength in the non-layup direction, and more exotic titanium blends using ceramic crystals.

Specialized did a metal matrix (instead of epoxy matrix) bike back in the '90s, but there were issues with it that I don't totally understand - it was not a "fiber" bike, though - it was still isotropic, so behaved like a metal rather than an anisotropic composite, and since most of the loads in bikes are highly directional anisotropic materials, for the most part, can be designed into better-performing things.

However, carbon-epoxy composites are brittle, so it occurs to me that a carbon-metal composite could be much stronger, while maintaining some of the directional properties of all-carbon bikes. It's a goofy interest, because the stuff out there has been "good enough" for quite a long time (no significant performance gains in most applications), but - hey bikes are cool and using exotic aerospace stuff is really cool.

Thanks again for exposing this interesting company.

[berserk87]

Originally Posted by cgates66

Specialized did a metal matrix (instead of epoxy matrix) bike back in the '90s, but there were issues with it that I don't totally understand - it was not a "fiber" bike, though - it was still isotropic, so behaved like a metal rather than an anisotropic composite, and since most of the loads in bikes are highly directional anisotropic materials, for the most part, can be designed into better-performing things.

I test rode one of these metal matrix bikes back then. My impression was that it was like riding a bike made of concrete tubing: stiff, but with a dead feeling to it. Maybe others felt the same way.