Ride or Replace?

[gaijintendo]

Surely this is an excuse to go fork shopping, and therefore a good thing.

 

[I like Skol]

Have you got any idea what goes into checking the structural integrity of carbon composites?

Yes thanks.

Please tell me what the next step would be if it was suspected that there might be more than just paint damage. I am genuinely interested because I have three bikes with carbon forks in Skol Towers.

I'm still waiting/hoping for a reply to this because I think I could learn something valuable from a genuine knowledgeable answer.

 

[Wobblers]

I'm still waiting/hoping for a reply to this because I think I could learn something valuable from a genuine knowledgeable answer.

You can use ultrasound to inspect carbon fibre parts. The ultrasound will reflect off areas that have delaminated internally, which can be detected:


View: https://www.youtube.com/watch?v=MPUoJBdulpo

 

[KnackeredBike]

You can use ultrasound to inspect carbon fibre parts. The ultrasound will reflect off areas that have delaminated internally, which can be detected:

I work with ultrasound on a daily basis and call bullsh*t on that video.

Firstly ultrasound requires a good contact with the surface to get a meaningful result - hence the gel used when doing a medical scan. If you just tap a scanner against a carbon fork you get sod all.

Secondly, ultrasound is good at imaging things with different densities, like a solid encased by liquid (hence a medical-grade one will get a blurry outline of a baby). Finding carbon delaminations is tricky but a skilled operator will get one on something with fairly consistent material either side, like a boat hull. On a carbon fork even with a decent scanner, which the video doesn't have, you would struggle to get anything meaningful.

In short, the video is a demonstration of how to tell a customer "I have ultrasound scanned your forks and I'm afraid you need new ones". Other than that it is valueless.

 

[Wobblers]

Another illusion shattered. Sigh!

Looks like you'll just have to borrow the local hospital's CT scanner, @I like Skol

 

[Yellow Saddle]

I'm still waiting/hoping for a reply to this because I think I could learn something valuable from a genuine knowledgeable answer.

It is tested by engineers who specialise in non-destructive testing methods. In the case of damage to carbon fibre composites they would firstly do a visual inspection against what they know about the structure i.e. thickness, mode of stress in that area (compressive or tensile) and then relative damage in terms of thickness left vs thickness original etc.
Then, if a crack is suspect, they would spray the part with a penetrative dye and developer. That would then be washed off and any residual dye left over in the crack would show up. If there is a crack, it would be juxtapositioned against specific areas of stress/no stress and an opinion rendered.
Then you'll receive a written opinion and more important, an invoice.
One can buy penetrative dye from companies such as Spanjaard but you need to know a bit about composites and crack propagation to interpret the results.
Due to cost, this is obviously out of the question, considering how cheap new parts are. However, an experienced mechanic can manipulate the part and listen for noises which would indicate cracks and give a similar verdict. An experienced mechanic with some experience could also just look at it and see that there's no cracks and say, go for it. One with such experience will not take a chance when it comes to steerer damage. However, fork blade damage is a different story and gives a better margin of error. If the part doesn't creak or cracks don't open when the fork is bent away from the scrape, you're OK to go.

 

[Globalti]

This is my buddy's RH chainstay after he had a collision with a car, hard enough to bounce the bike right onto the top of a high hedge 15 feet away. As you can see the actual resin has cracked under the impact along the lines of the wraps of carbon fibre. However the carbon fibres encased in the resin are largely intact and the bike was still rideable (we tried it) because 2/3 of the circumference of the stay was undamaged and this is only one of a pair of stays.

What I'm trying to illustrate is that in my opinion impact or friction damage to a carbon component is likely to show as failure of the resin long before complete failure although of course under massive structural load a carbon component can fail catastrophically as we've all seen in videos.

 

[Mr Celine]

I think the OP should be more worried about tripping over the garden hose and breaking his neck.