https://www.dailymail.co.uk/news/article-12225371/James-Cameron-told-MONDAY-sub-imploding-detected-claims-carbon-fibre-hull-unsuitable.html

Titanic movie director James Cameron says he was told on
MONDAY that the sound of the Titan sub imploding had been
detected, and claims the carbon fiber hull of the doomed
ship was known to be unsuitable

.. . .

Looks like he has good connections.

And he's right - carbon-fiber/epoxy IS strong, but
not necessarily in the right ways for THAT particular
application.

It's not the carbon fiber - it's the epoxy. It develops
fatigue cracks and/or 'creep', under repeated high loads.

The worst case was the infamous Boston Tunnel ... epoxy-
fixed bolts 'crept' under sustained load and soon the
whole roof caved in with many casualties.

The problem - the carbon fiber is much harder/stronger
than the epoxy goop supposedly holding it together.
Think steel wires stuck-together with Jello. Under
repeated extreme stress .....

Now monolithic clear polymers like polycarbobate,
you might SEE the fatigue happening, but NOT with
something made opaque with carbon fibers.

Cameron is well-informed here. He designed his own
super-deep sub, and crush pressure was always the
#1 concern. The whole design HAS to be wrapped
around this threat.

The common fixes - steel or even titanium spheres
for the pressure vessel. Really thick polycarbonate
will also work - but overall the design needs to
be a pretty much perfect sphere. Metal is much
more suited to these problems. Alas it's MORE
EXPENSIVE, and the sub boss here went with the
inferior, cheaper, material. Enough dives and ...
BOOM !

OTOH, these 'adventures' are mostly for really
bored super-rich people. I say LET THEM book
such things. Inform them properly, have them
sign the waivers ....

And yes there are similar 'adventures'. Jeff
Bezos's GiantPenisRocket, Bransons "orbital
plane", even Musk allows those with enough
money to book his rockets to orbit or the
ISS. (interesting how HE has never been a
passenger :-)

All these things are Super-Dangerous, on
The Edge. Some people really get off on
that- it's their "test". OK, so be it.

As for Cameron ... his little group of
super-adventurers KNEW that sub was
seriously sub-par and KNEW there was a
big disaster looming. Nothing they
could DO about it though - other than
NOT TO BOOK. The TV adventurer Josh Gates
took ONE ride on the thing - and then
REFUSED a second when offered. He's not
an engineer, but still could TELL that
very bad things were gonna happen.

On 6/23/2023 1:50 AM, 34J.935 wrote:
> https://www.dailymail.co.uk/news/article-12225371/James-Cameron-told-MONDAY-sub-imploding-detected-claims-carbon-fibre-hull-unsuitable.html
>
> Titanic movie director James Cameron says he was told on
> MONDAY that the sound of the Titan sub imploding had been
> detected, and claims the carbon fiber hull of the doomed
> ship was known to be unsuitable
>
> . . .
>
>   Looks like he has good connections.
>
>   And he's right - carbon-fiber/epoxy IS strong, but
>   not necessarily in the right ways for THAT particular
>   application.
>
>   It's not the carbon fiber - it's the epoxy. It develops
>   fatigue cracks and/or 'creep', under repeated high loads.
>
>   The worst case was the infamous Boston Tunnel ... epoxy-
>   fixed bolts 'crept' under sustained load and soon the
>   whole roof caved in with many casualties.
>
>   The problem - the carbon fiber is much harder/stronger
>   than the epoxy goop supposedly holding it together.
>   Think steel wires stuck-together with Jello. Under
>   repeated extreme stress .....
>
>   Now monolithic clear polymers like polycarbobate,
>   you might SEE the fatigue happening, but NOT with
>   something made opaque with carbon fibers.
>
>   Cameron is well-informed here. He designed his own
>   super-deep sub, and crush pressure was always the
>   #1 concern. The whole design HAS to be wrapped
>   around this threat.
>
>   The common fixes - steel or even titanium spheres
>   for the pressure vessel. Really thick polycarbonate
>   will also work - but overall the design needs to
>   be a pretty much perfect sphere. Metal is much
>   more suited to these problems. Alas it's MORE
>   EXPENSIVE, and the sub boss here went with the
>   inferior, cheaper, material. Enough dives and ...
>   BOOM !
>
>   OTOH, these 'adventures' are mostly for really
>   bored super-rich people. I say LET THEM book
>   such things. Inform them properly, have them
>   sign the waivers ....
>
>   And yes there are similar 'adventures'. Jeff
>   Bezos's GiantPenisRocket, Bransons "orbital
>   plane", even Musk allows those with enough
>   money to book his rockets to orbit or the
>   ISS. (interesting how HE has never been a
>   passenger :-)
>
>   All these things are Super-Dangerous, on
>   The Edge. Some people really get off on
>   that- it's their "test". OK, so be it.
>
>   As for Cameron ... his little group of
>   super-adventurers KNEW that sub was
>   seriously sub-par and KNEW there was a
>   big disaster looming. Nothing they
>   could DO about it though - other than
>   NOT TO BOOK. The TV adventurer Josh Gates
>   took ONE ride on the thing - and then
>   REFUSED a second when offered. He's not
>   an engineer, but still could TELL that
>   very bad things were gonna happen.

Off hand, I believe the composite would hold if pressure was inside but
on the outside composite shear strength would come in. Pressure at
depth would be nearly 6,000 psi and shear strength of epoxies is about
10,000 psi. That is too close and values go down under continuous
stress and are much less.

Fiber composites are not isotropic in that properties are not the same
in different directions of stress. A design engineer is stupid if he
does not know this.