Solid Carbon Fiber Knives

[richie191]

The process is called galvanic corrosion. When two materials with different galvanic constants are put in contact with an electrolyte, an electric circuit forms and one of the one with the lower galvanic constant corrodes. It's the same reason why you see a lot of corrosion where steel and copper plumbing is connected.

It really shouldn't be a problem with a laminated knife unless it spends a lot of time around salt water. In most high moisture applications where carbon fiber and steel are bonded together, a thin layer of fiberglass is between them.

Thank you a lot, it's nice to know. I am screwing two carbon scales around a 1/32" piece of steel, and I had no idea it could corrode. I'm using screws without adhesive because I don't like the idea of just an adhesive holding it together. A few pins are another option, but I'm going to make some with just screws so that it will be surely mechanically held together, and even be able to be taken apart. Do you know where I could get super-thin fiberglass? Thanks again.

God Bless,
Richard

 

[fod]

Thanks.
Electrolytic action I could understand. If the CF was bonded with a resin ( as described) I don't see any real worry on a knife blade.
Stacy

Stacy,

For those using laminated sheets it is probably a non issue. Perhaps if the laminate is ground exposing the CF fibers, but the epoxy line will most probably keep the steel from direct contact. There are issues with bonding to aluminum and corrosion that I can find in in "library". Some issues can arise from the hygroscopic nature of some resins, but again for these applications we are discussing here they are moot and proper lay up techniques will minimize these issues. We need not worry about the types of fatigue and corrosion worries aircraft manufacturers are concerned with.

I cannot find the research that I did when working on the project with the flashlight maker that led me to believe there was a (potential) corrosion issue. Even if I did recall correctly, I am sure it is a non-issue for the applications considered here. I did find that nearly all CF has been surface oxidized to ensure proper and consistent bond to the to the resin matrix. And perhaps what I am recalling was peculiar to aluminum.

CF is wild stuff and has some properties that may or may not be of concern to those considering this type of project...it has a CTE (coefficient of thermal expansion) of zero. So it will not expand and contract with temperature changes. Of course steel will, so perhaps there is a chance of popping the bond with temp swings. May or may not be an issue.

Also, CF (specifically some of the pitch types of CF) is very efficient at transferring heat, some grades doing better than aluminum, copper and silver. As mentioned it is electrically conductive. It can make excellent heat sinks.

Of course, the resin matrix will have an effect on these properties.

Regards,,
-Todd

 

[artmichalek]

Thank you a lot, it's nice to know. I am screwing two carbon scales around a 1/32" piece of steel, and I had no idea it could corrode. I'm using screws without adhesive because I don't like the idea of just an adhesive holding it together. A few pins are another option, but I'm going to make some with just screws so that it will be surely mechanically held together, and even be able to be taken apart. Do you know where I could get super-thin fiberglass? Thanks again.

God Bless,
Richard

Fiberglass would probably be overkill in your case. If you really want to be extra cautious, maybe spray the insides of the scales with an acrylic clear coat. Then just keep an eye on it. Even in the presence of an electrolyte galvanic corrosion takes quite a while to happen. If your knife is stored and used in dry conditions it may never be a problem.

 

[langchop]

Wow... never heard of Cf knives before but they really do look smashing and a definate prospect for a future project.

 

[Jim L.]

Or maybe like this?

I must have been the first to inquire about a production run, because he gave me dibs on the #2 Ultralight. Lucky me!

Pretty cool. Where can you get this stuf and what's the cost?

Jim L

 

[richie191]

Pretty cool. Where can you get this stuf and what's the cost?

Jim L

You can get the green carbon fiber mix from fibermascus.com . I personally am using solid carbon fiber since I know the strength of it. I am unsure how strong a mix of carbon fiber and some other type of material would be, although it does look cool. I'm in the process of making my first carbon fiber sword. It is two pieces of carbon fiber sandwiched around a .047" thick piece of Crucible CPM-3V. Handle is around 5" and blade is around 20". Wish me luck!

God Bless,
Richard

 

[Jim L.]

You can get the green carbon fiber mix from fibermascus.com . I personally am using solid carbon fiber since I know the strength of it. I am unsure how strong a mix of carbon fiber and some other type of material would be, although it does look cool. I'm in the process of making my first carbon fiber sword. It is two pieces of carbon fiber sandwiched around a .047" thick piece of Crucible CPM-3V. Handle is around 5" and blade is around 20". Wish me luck!

God Bless,
Richard

That might br pretty cool. Can't wait to see the end results.

Jim L.