[Closed] How do you check for carbon frame damage?

Look at it carefully to start. Try tapping it with a coin and listen out for a change in tone. A dull thud instead of a high pitched sound is bad.

Bin it and claim a new one from the drivers insurance.

You can never be sure, [url= http://www.bike-manual.com/brands/fisher/om/track/carbon_fiber.html ]"a damaged carbon part (with reduced strength due to the damage) may look normal"[/url]. Take it to a dealer for their opinion, which may be that it's a write-off

Previous experience of this in our club is that you should get a new frame. The only real way of telling is a mixture of xrays and ultrasound and even that is not perfect. If the drivers insurance company are informed then they should replace it - otherwise they can be liable if it falls apart when you are riding!

Watch out for the insurance assessors though - one of our guys got rear ended by a taxi and they sent out someone to inspect the bike. Normally looks at cars, no idea about bikes, never inspected carbon fibre, no knowledge of the material....... yet he is their expert opinion!

Tapping a cf frame with a coin doesn't tell you anything unless you are intimate with the frame's specific layup. Ratio of cloth/resin, style of joint construction, layup pattern,etc all have a large influence on the "sound"

If the frame is checked for alignment using the specific toolset, and is found to be as normal, and there is no external evidence of structural damage I.e. witness marks its probably not damaged.

Some shops I worked for had a strict "write off" policy for customers with insurance who had been involved in rtc with motor vehicle; the shop did not want to be liable and the insurer would replace the frame/ bike

big problem in the aero industry according to a mate who works in that field. apparently service vehicles are frequently bashing in to aircraft. easy to identify with aluminium, not so much with your crabon. bin. new frame.

I really can't think of any dealers I'd trust to make that call. Not sure importers would be much better. Perhaps trust a manufacturer if they actually make them. Not sure what they could do beyond checking alignment.

Get the frame alignment checked and give it a thorough visual inspection - if the frame has has an impact there's usually some sort of crazing, cracking or bruising. Ultrasound can detect delamination. I've been riding a cracked and bruised frame for years as has a friend who had a big stack on theirs - they're stronger than most folk think. Still claim for a new frame from the insurance, but negotiate a deal on the old one..

Alignment won't tell you much as a composite bike won't distort like a metal one until there is an obvious bit of damage.

It's probably okay but no sensible (cost) way to be sure so safest bet is replacement.

Who's ever seen any evidence as to invisible damage to CF frames?

About 10 years ago I got the 'big scratch/small crack' question resolved by popping it through the x-ray machine at my local RAF base. If you know anyone who access to that sort of kit give them some beer and ask for a favour.
My frame was ali though, not sure if that makes a difference

I asked to look when I first flew to NZ and it went through the scanner at Customs in Auckland, them Kiwi's are nice enough not to care 😉

This mantra about X-raying frames gets my goat. Firstly, unless you have privileged access like the poster above, who is going to let you stick a bike through their X-ray machine? Secondly, what would it show? X-rays are for examining invisible items inside other items. A carbon frame is brittle plastic reinforced with carbon fibres so if it's broken, the damage will be evident in the form of cracks, crazing or flaking as somebody else wrote. A damaged tube will be able to be crushed between the fingers, making a loud cracking noise.

Just give the forks a good pull and push while listening for creaks and check every inch for superficial damage.

NDT inspection of carbon is difficult and even purpose built inspection machines are not 100% effective and often in industry the coin comes out and a tap test and the MK1 trained ear comes into play. You have 2 choices - risk it or try to claim for a new frame.

However, with my very rudimentary understanding of composites, I would have thought that on a thin walled tube, if the tube was bent to the extent that damage to the internal carbon structure or delimitation has occurred then you should see some visible sign of it ion the surface of the tube - either cracking or damage to the paint. The biggest issue I see in industry is with larger, thicker carbon structures - i.e. half an inch thick panels where often you cannot visibly inspect all of the panel due to it's installation.

If you can claim for a new frame, then i'd do it.

Have spoken to a solicitor - advised to get it checked out by a bike shop.
I won't go into all the details of what happened here (another thread up and running) but I'm claiming for kit damaged during incident - plus getting bike checked over for peace of mind.
Guessing this is hardly going to be conclusive one way or the other and whatever conclusion they draw will be with a big caveat. I'll take it to a couple and see what they say.

In aero you do design for barely visible impact damage.

I would hope that any sensible frame manufacturer would also design for this - it could be from any source - transport, dropping the bike, dropping a tool on the bike etc. Luckily CF is pretty strong so you can still make stuff lighter even accounting for this.

Accurate inspection of composites is difficult.

I once did a project on impact damage to composite structures as part of my degree. It is a big concern in the aerospace industry.

From what I remember its quite common for there to be no visible damage to the part on the impact side, but delamination of the layers of composite in the material can reduce it's strength. Remember that composites rely on the different layers of fibres adding strength in different directions. If they are no longer bonded together the material will no longer work as designed. Not good in a skinny seat stay for example.

The delamination might be more apparent on the other side of the material from the actual impact, but you can't see this in closed tube like a seat stay.

I'd say bin the frame and claim on their insurance.

Mate at work has just got his old bike back from the shop, they've written the frame off after he was rear ended.

No visible damage but they can't be sure so have priced up a replacement. It's a Madone 6.9 so the insurers are going to get a bit of a shock, as is the plonker that hit him and keeps leaving him angry voicemails