Great source of info, Court. Thanks for sharing.
No wonder we are witnessing huge number of bikes with Carbon frames ( weight savings ~ 3kgs).
As a nanotechnologist who has worked on graphene and carbon nanotubes, I have seen remarkable progress in the processing of carbon composites in the last 4 years alone.
- When made with the appropriate resins, carbon fiber is one of the most corrosion-resistant materials available.
This is the key point. Carbon fibers are brittle but so is hydroformed aluminum on many bikes but the key is making layer-by-layer composites either by spinning or coating and you get phenomenal strengths. Most TIG welded structures have something called heat affected zone (HAZ) that are prone to failure. Steel is tougher and that is why you see that necking. Carbon can be made tough as well.
Regarding your points on resistance to scratching, it highly depends on what type of QC was implemented at the manufacturing facility. Most of them use some kind of surface coating (
a quick YT search yielded this). If they used large pieces then crack propagation could be fast but these days molding process is changing rapidly. Just like how we have different variety of Lithium-ion batteries, carbon frame quality varies. Some batteries die in a year or so while others last for 3-4 years.
Tesla even promises 8 year battery life at ~ 70%.
So, carbon is a great material but its manufacturing process, QC, material source etc., all matters. Even light-weight hydroformed aluminum cracks because we have all this fancy hollow tubes for running the wires, welded spots for braze-ons etc. A bike owner can not go and check all these intricate details, so better to have a solid warranty from reputed manufacturers before shelling out lot of cash.
A sample video of what is involved in carbon bike frame manufacturing.
