carbon fiber frame specifics

[gefiltephish]

Hello... I'm comparing the embedded energy and environmental / human health impacts of different frame materials of all portions of their life cycle (raw materials, manufacture, distribution, use, end of life) using material flow analysis and impact assessment.

Information for steel and aluminum has been accessible in scholarly journals and a great manufacturing over is here: http://thesustainablecyclist.com/2009/07/26/bridgestone-on-frame-materials/

I'm looking for similar information on carbon fiber frames... I'm assuming that 'carbon fiber' bike frames are "carbon fiber reinforced with epoxy polymers."

Here's what I know for the manufacture:
Textile manufacturing and prepreg preparation
Integration of fibers and polymer resins (epoxy?)
Heat and pressure needed during curing phase

Any insight into specifics of materials or manufacturing processes specific to 'carbon fiber' bike frames would be great... lots of info out there, but bike specific stuff seems to be 'out of the public eye,' as it's likely proprietary....I'm interested in what the industry 'standard' is (if there is one), not cutting edge techniques (i e usingorganic fibers) All I've found is how to make the PAN carbon fiber filaments: http://www.carbonfiber.gr.jp/english/tanso/04.html


Thanks for any insight... I will be sure to post the finalized report, which will no doubt be interesting (ever wonder how your metabolism effects the environment?)

[chaostactics]

i dont know much about carbon fiber but what about mag and ti for bike frames and componetry

[gefiltephish]

For the LCA report I think carbon fiber reinforced with synthetic composites like epoxy resin juxtapose the ore extraction and extensive processing of ti, al, mg... Carbon fiber has a lot of embedded more material versus process energy

I guess specifically I am shaky on how the 'fossil fuels' become carbon fibers and epoxy resisns, and those become tubing or bike frames

aahhh savation ---> http://www.compositesworld.com/articles/the-making-of-carbon-fiber.aspx

[jmblur]

There are a few suppliers of prepreg materials, but a lot of the more vertically integrated suppliers make the prepreg in-house. Other than that, there's the big guys, like Mitsubishi (yes, that mitsubishi). The process of making prepreg is something that's a bit out of my knowledge, sorry.

As for the process of actually making it into bike frames, there's two main methods: bladder molding and mandrel/vacuum bagging. Bladder molding uses an exterior mold (generally metal) and a shaped balloon; the carbon fiber is laid up by hand in the mold (or around the bladder on a mandrel support), the mold is closed, and then the bladder inflated to push the composite into shape against the mold. Bladder molding gets the best external surface detail as it matches the metal pretty closely.

Mandrel/vacuum bagging is a similar process, but the material is compressed via an external bag instead of a mold; the shape comes from the mandrel underneath. External edges are smooth and rounded, while the internal shape is almost exact to the mandrel.

There are some other processes out there as well, such as pulltrusion, but I'm not as familiar with them.

There are also a few techniques for putting the frame together. The whole frame can be done as one large component (generally vacuum bagged), or individual components can be combined with lugs to make a frame. Generally, with tubing shaped carbon frames, lugs will be used; with fancy shaped frames, they'll make the whole damn thing at once.

A few other notes:
1. All lay up is currently done by hand. For complex parts, this is done with "flags", or specially cut shapes designed to put the proper amount of material in the proper fiber orientation. For tubes and other more regular structures, you can filament wind, or use "tape", which is exactly what it sounds like (using unidirectional carbon fibers).

2. The carbon fiber weave you think of when you hear "carbon fiber" is exactly that, a weave. however, it tends to be quite heavy and thank, and not all that strong compared to unidirectional layers laid up at carefully defined angles. however, weaves tend to produce less-sharp edges than unidirectional fabric when there's failure, so weaves are somewhat safer. Weaves are also very expensive, so most carbon fiber parts you see that look woven are either only an exterior woven layer, or a decal made to look like a weave (the decals have gotten VERY good recently).

3. There are some emerging technologies that use machine placed flags, Toyota is looking into them currently iirc.

There's lots more info out there, but this should hopefully get you a good starting point. I don't know much on the epoxy production side, and I simplified (probably oversimplified) the manufacturing techniques above, but it should give you some good keywords for googling!

[walsh]

For your task, I would consider the data available on the use of structural carbon composites in the aerospace industry (where a lot of the inital development occurred) and scale down for bicycle frame manufacture.

Even setting frame material aside, there are a LOT of ways to assemble a bike. In order to compare apples to apples, you might first examine the manufacturing processes for producing a complete tubeset in carbon, aluminum and steel (and titanium if you feel cheeky), and make that the basis of your comparison. Just make the assumption that the frames are bonded in a comparable manner.

Later, if you want to get fancy, look at the differences in energy and material use during fillet brazing, TIG welding, and epoxying lugs.

[Dr Phil mmkay]

Ibis has a pretty good write up here (http://www.ibiscycles.com/tech/technology/). I remember back in my car-guy days, there was always a toss up as to the cost/benefits of picking 'dry-carbon' parts over 'wet carbon' parts (hoods, fenders, bumpers, wings).

Since Ibis uses a pre-peg method, does this mean their frames are considered 'dry-carbon'?

[gefiltephish]

the report is done! The complexity of the life cycle analysis meant that I couldn't get too much descriptive or quantitative detail for bike-specific manufacturing of cf, steel, or Al, but I do think the embedded energy and impact assessment of the materials is pretty accurate.

Have a read at: http://rapidshare.com/files/318015986/Bicycle_Frame_LCA_v2.doc.html