Talk Composites - The Forum for Advanced Composites

Need help on a Carbon frame analysis

http://www.talkcomposites.com/Topic34765.aspx

By Freitasdh - 2/5/2020 1:27:55 AM

Recently a friend of mine identified a crack on his bike frame.
He tried to solve it thru warranty but after tons of emails trying to prove that it was a manufacture issue, they came with a internal picture and said that the crack happened due to an external impact.
Based on only one pic....
I’ve attached the pic bellow. So I’m wondering, looking at it, can you assume it suffered an external impact?
If anyone can help us, please get back to me.
All the best.
Lucas.

By oekmont - 2/8/2020 4:25:25 AM

The picture is very bad. As you found the crack, I guess you can see it from the outside. What do you mean by "internal"? Is it an endoscope picture? If so, the crack seems to go from the outside inwards, through the whole laminate.

Sorry for your friend, but you can say that a crack like this only happens through an external forces. Additionally, carbon composites have excellent alternating load propertys. If the frame made 2 years without getting this crack, it is extremely unlikely that it will get damaged by regular use.

I am pretty sure that something happens to this frame. Maybe an impact, maybe jamming or inappropriate clamping during transportation.