Hairline cracks in Carbon Frames

[SL7]

Hello to all you stressed people in CT and elsewhere

 

Is there a method to detect hairline cracks or weaknesses in a carbon frame when buying second hand?

 

Maybe the CT weather will let up soon and we can go for a ride.

 

 

[spano]

Why do you ask? are you looking to buy a carbon frame or do you want to check your own one?

 

 

 

The only thing i can think of is to have it x-rayed, or perhaps checked with ultra sound or something,,, but its gonna cost you!

[Christie]

No easy to do non destructive tests available at the moment. X-rays & ultrasound don't work. Dye penetrant is also a wase of time - it only shows surface flaws, and lmost carbon frames come from the factory with some surface flaws - a small hole in the surface epoxy does not weaken the structure. (The results of a dye pen test on a carbon frame can be quite scary to see, even though the frame is actually ok) 

 

Infra red thermography has potential, but the equipment is expensive, rare and the flaws in test samples I was involved with were not detected.

 

Best NDT imo is to measure vibration frequency response functions between several points on the frame. Will need to measure a new frame, and the used frame, though, of exactly the same design. If the frequency of resonant peaks are much lower on the used  frame, it means that stiffness is lower, which can only be due to dammage.

 

[Dirtbreath]

 

No easy to do non destructive tests available at the moment. X-rays & ultrasound don't work. Dye penetrant is also a wase of time - it only shows surface flaws' date=' and lmost carbon frames come from the factory with some surface flaws - a small hole in the surface epoxy does not weaken the structure. (The results of a dye pen test on a carbon frame can be quite scary to see, even though the frame is actually ok) 

 

Infra red thermography has potential, but the equipment is expensive, rare and the flaws in test samples I was involved with were not detected.

 

Best NDT imo is to measure vibration frequency response functions between several points on the frame. Will need to measure a new frame, and the used frame, though, of exactly the same design. If the frequency of resonant peaks are much lower on the used  frame, it means that stiffness is lower, which can only be due to dammage.

 

[/quote']

 

Could this be done on an aluminium frame as well?

 

[Christie]

Could this be done on an aluminium frame as well?

 

Yes, method will work perfectly on any frame material. Only problem is that the need for a "reference" frame. 

 

What could work well is to measure your brand new frame.This is then the reference measurement. Then have it measured again after a couple of years of hard riding. If the frequency is more or less the same, the frame stiffness is the same, meaning you can ride on without worry.

 

BUT

 

I must also say, imo most frames are fairly tough and hold up very well, elaborate testing not is neccesary in 90% of cases 

Christie2009-06-24 13:29:06

[turtlek]

best idea that i ever got and has worked for me is the coin test

 

 

 

tap the coin over a piece of carbon that you can see doesnt have any abrasions and then tap it over the affected/suspected part and if the tone changes then get it checked out by a guy who knows what he is talking about

 

 

 

christie is 100percent correct all those methods either dont work or are just scary to see and if they do work they are very expensive

[SL7]

Thanks this is helpful.

 

Not buying at this stage - but the knowledge will be useful when I do!