New evidence strongly suggests that OceanGate’s submersible, which imploded and killed all passengers on its way to the Titanic wreck, was unfit for the journey. The CEO, Stockton Rush, bought discounted carbon fiber past its shelf life from Boeing, which experts say is a terrible choice for a deep-sea vessel. This likely played a role in the submersible’s tragic demise.
From my limited experience with laying up carbon fiber, I know there’s the raw carbon fiber cloth and there’s liquid resin that you spread into the cloth. It’s also very common to see carbon fiber cloth that is “pre-impregnated” - the resin is already applied to the cloth. Everyone calls this “pre-preg”.
So I’ve seen a lot of folks online scratching their heads about “how can carbon expire?” or “my carbon fiber (bike/boat/etc.) is N-years old, is it expired?” but I think the most likely thing to expire is the resin. Once the resin is cured it is much more stable.
Any materials folks or structures engineers who want step in and correct me, please do.
Also most bikes aren’t under enough pressure to cause them to implode
Not with that attitude.
Actually CF road bikes only have a safe lifespan of about 10 years - https://icancycling.com/blogs/articles/lifespan-of-road-bike-frame
<insert yo mama joke here>
Different loads, different failures, but still a valid safety concern.
I would not want my bike frame or fork to be made with expired resin. But the age of the bike after the CF is cured is a different matter.
Different loads, different failures, but still a valid safety concern.
I would not want my bike frame or fork to be made with expired resin. But the age of the bike after the CF is cured is a different matter.
Well it would have an expiry if purchased from Boeing. All materials used in aircraft have stringent performance requirements. Resin is a plastic and like all plastics it degrades over time. It can lose strength and fail to meet materials ratings. Now if you wanted to make something like a regular boat hull out of the stuff it would probably last a lifetime, but if you want to make something like an airplane wing, that’s a different story.
Anyway carbon fiber composite is stronger and lighter than steel, but the wonderful thing about metals is they can have good properties for supporting all kinds of loads. But even then you have to inspect for fatigue on a regular basis when loads cycle repeatedly. Carbon fiber doesn’t do as well with that.
I agree with all of that. My intuition is that prior to curing, the polymers are less stable and may change in unpredictable ways depending on subtleties in the storage environment and handling. After curing, the polymers are much more stable and durable.
Metals definitely are more forgiving, and we have better tools for testing, especially non-destructive testing. Whether the CF flaws are due to fatigue or workmanship, it’s easy to miss them in inspection.
I’m also curious what the sub designers saw as the advantage of CF for this application. Is light weight really all that advantageous for a submersible? Generally no one chooses CF if they are prioritizing cost.
I don’t see where it fits as a good solution either. Typically it’s used where weight is the main consideration, such as in aircraft. CF is more expensive, has higher maintenance cost, and more difficult to produce than metal. Was it more about doing something different than doing it better? Well the tried an true method for deep sea submarines is a titanium sphere and that’s quite expensive so it probably was a lot cheaper.
In his scenario weight was a factor.
They were trying to get the sub to be as light as possible so it could be operated from nearly any vessel. The goal was to have the sub and a launch sled that could be launched and recovered aboard a rented ship. This was all to save money; they didn’t want to have to purchase and outfit a special purpose support vessel.