Super Glue the cured carbon?

[BenCarbonNovice]

Dear community,

I am working on a very small carbon repair, and the challenge is that I have limited access to the repair area; it will be difficult to set up vacuum bagging.  When I say "small", I am referring to physically small.  The total carbon patch will be in the neighborhood of about 8mm by 15mm.

This repair is to be on a bicycle...the inside of the head tube.   For those of you that know bikes, this happened with a headset removal tool.  For those that don't know bikes, consider a screwdriver gouging out one layer of carbon.  The tube itself has two spots, one that is thin (about 3mm) and one that is thick (about 10mm).  The damage is in the spot that is thick.

If I had easy access to set up vacuum bagging, I would layer on a few new layers of carbon, alternate orientation between layers, and vaccuum it with proper bleeder and such.  However, setting up a a vacuum bag will be tricky.  Not only are there two different internal diameters, there are some complex shapes in there that get in the way.  Thus, I begin to ponder this idea...

What if I create a mold of the inside of my tube, and used that mold to fabricate the carbon patch, (properly, with epoxy).  Once my precise carbon patch is fabricated, I can use a cyanacrolate to glue it into place.

I see these advantages:

• I get unlimited "do overs".  When I make mistakes, I'm not working with epoxy on the inside of my frame.  The amount of carbon I'm using is really tiny (think postage stamp), and I have a yard of it.   That to say mistakes with the carbon are not a problem.
• Similarly, If I mess up when gluing the patch into the fame, I can use acetone to get it out and try again.
• Getting a vacuum seal will not be problematic, well at least not more problematic than normal.

I wonder about these disadvantages:

• Am I compromising structural integrity?
  I am inclined to think not.  The bond does not need to resist impact, just resist movement, so that the new carbon can share the load with the old carbon.
• Will there be a mismatch between the elaticity of the carbon, and with the glue?
  Again, I dont think so because... A)Dragon plate sells a cyanocrolate for joining carbon parts, and B) There appears to be a good elongation match.  MDS for each suggest about 2% for the superglue, and 1.7% for the carbon I'm using.
• It might be hard to the the mold just right.  But this is made up for by the unlimited do-overs.
• If there is a gap when I glue in the final patch, I won't know, although that would be true of an air bubble if vaccuuming in epoxy, so I'm not sure is more or less problematic than the

I recognize that I have limited experience, most specifically... I don't know what I don't know.  Thus, a dangerous place on the dunning-krueger curve.  (look it up if you are not sure what that is)

Lastly, this topic is not about whether or not this bike it is safe to ride.  In fact, I have even considered riding it as it is.  This frame is very robust, made by a highly reputable manufacturer.   The damaged carbon has been removed, and I don't see any cracks protruding into the healthy carbon, and most importantly, the damage is at a spot that is very thick.  I'm not concerned about a failure that would cause injury.  Rather, I want reduce the chances that a crack develops over time, leading to the point that I should retire the frame.

Ideas and suggestions that are not directly related to the superglue question are welcome.

Ben

 

 

 

[lo_0l]

1 hour ago, BenCarbonNovice said:

Dear community,

I am working on a very small carbon repair, and the challenge is that I have limited access to the repair area; it will be difficult to set up vacuum bagging.  When I say "small", I am referring to physically small.  The total carbon patch will be in the neighborhood of about 8mm by 15mm.

This repair is to be on a bicycle...the inside of the head tube.   For those of you that know bikes, this happened with a headset removal tool.  For those that don't know bikes, consider a screwdriver gouging out one layer of carbon.  The tube itself has two spots, one that is thin (about 3mm) and one that is thick (about 10mm).  The damage is in the spot that is thick.

If I had easy access to set up vacuum bagging, I would layer on a few new layers of carbon, alternate orientation between layers, and vaccuum it with proper bleeder and such.  However, setting up a a vacuum bag will be tricky.  Not only are there two different internal diameters, there are some complex shapes in there that get in the way.  Thus, I begin to ponder this idea...

What if I create a mold of the inside of my tube, and used that mold to fabricate the carbon patch, (properly, with epoxy).  Once my precise carbon patch is fabricated, I can use a cyanacrolate to glue it into place.

I see these advantages:

• I get unlimited "do overs".  When I make mistakes, I'm not working with epoxy on the inside of my frame.  The amount of carbon I'm using is really tiny (think postage stamp), and I have a yard of it.   That to say mistakes with the carbon are not a problem.
• Similarly, If I mess up when gluing the patch into the fame, I can use acetone to get it out and try again.
• Getting a vacuum seal will not be problematic, well at least not more problematic than normal.

I wonder about these disadvantages:

• Am I compromising structural integrity?
  I am inclined to think not.  The bond does not need to resist impact, just resist movement, so that the new carbon can share the load with the old carbon.
• Will there be a mismatch between the elaticity of the carbon, and with the glue?
  Again, I dont think so because... A)Dragon plate sells a cyanocrolate for joining carbon parts, and B) There appears to be a good elongation match.  MDS for each suggest about 2% for the superglue, and 1.7% for the carbon I'm using.
• It might be hard to the the mold just right.  But this is made up for by the unlimited do-overs.
• If there is a gap when I glue in the final patch, I won't know, although that would be true of an air bubble if vaccuuming in epoxy, so I'm not sure is more or less problematic than the

I recognize that I have limited experience, most specifically... I don't know what I don't know.  Thus, a dangerous place on the dunning-krueger curve.  (look it up if you are not sure what that is)

Lastly, this topic is not about whether or not this bike it is safe to ride.  In fact, I have even considered riding it as it is.  This frame is very robust, made by a highly reputable manufacturer.   The damaged carbon has been removed, and I don't see any cracks protruding into the healthy carbon, and most importantly, the damage is at a spot that is very thick.  I'm not concerned about a failure that would cause injury.  Rather, I want reduce the chances that a crack develops over time, leading to the point that I should retire the frame.

Ideas and suggestions that are not directly related to the superglue question are welcome.

Ben

 

 

 

Have pictures?