All the experts on carbon fiber are making videos now...
YouTube is filling up with videos now about how the OceanGate Titan submersible imploded. Fingers are pointing to the 5 inch thick hull 'spun' with carbon fiber claiming it was the culprit. They all say it was the materials used.The video below shows a machine winding a large metal tube with carbon ribbon about 4 inches wide the same way a spool of thread gets put on a bobbin. This is how the hull was created. Was the metal tube part of the hull or was it only used for the process of forming the tube? The first part of the building sequence it appears the tube had something applied first and it could be a 'release agent' used in mold making or the bonding adhesive and the metal tube was part of the hull.
Did the layers of carbon fiber get bonded with resins making a solid casting?
Other than the fibers appearing shiny, the process wasn't clear and I'm guessing the machine that applied the ribbon was laying it on 'wet' with resin applied.
The problem with that process is resin has catalyst and you are limited by the amount of time to work before it hardens. Laying up 5 inches could take all day... maybe longer and take several sessions. The first layers would be curing while the layers on top would be applied over it. That creates a weak point where the layers are attached.
Molded carbon fiber components are used in automotive and aviation sectors... they have been for many years. The process isn't new. The process turns bad when you try to add several layers as one because they each have a different curing rate and may not have a uniform bond between each layer.
Were any layers of carbon fiber running crossgrain (left to right) or did it all get wrapped in the same direction? The video shows all in the same direction of the cylinder.
Note, in woodworking, the strength of plywood sheeting is created by running the layers in different directions giving it stability. If all the layers are in the same direction, the wood becomes flexible. That rule of lamination applies to fiberglass and carbon fiber technology too!
I read that OceanGate CEO, Stockton Rush had a US Patent for a device to detect any sound or vibration that would indicate a stress crack in the hull. Maybe, I'll go into that part of the equation later.
From the look of things, the design had no internal ribs or supports.
The titanium rings on the ends were only glued in place. Only glue.
Say that again... Only glue.
What's missing in the construction??
The rings were applied to the OUTSIDE of the carbon fiber cylinder designed to withstand EXTERNAL pressure. Technical no-no.
I do cabinets for a living and have some model aircraft experience for 40+ years and things like that need both a mechanical and chemical bond.
Simple thought... anyone out there having done some soldering of 2 wires knows you first twist the wires making a mechanical connection before heating and applying the solder.
Did the people who designed the Titan forget the obvious...
There should have been double rings with bolts between them to 'sandwich' the hull to the end rings. Titanium and carbon fiber have different expansion/contraction rates so a mechanical connection should be first, with the glue/epoxy/sealant in between.
No assumptions, but let's say the external forces caused the carbon to flex more than the glue between the hull and the end rings, the failure really was the bonding agent and not the materials it was supposed to hold together.
Just a thought.
Another thought was the crane that hoisted the salvaged Titan submersible had a strap through the titanium 'door' where the viewport used to be.
Did it fail causing the craft to implode, or was it removed when brought on deck of the salvage boat making it easier to move it to the dock?
That may have been the weak link to the design and all the talk of carbon fiber would be meaningless.
Comments (10)
Like any rope.
The glue fixing the titanium to the fiber roll dont bother me a lot
as per defention one would do "without any"..
being the pressure from outside should push the two endcaps in place.
my2c
Like any rope.
The glue fixing the titanium to the fiber roll dont bother me a lot
as per defention one would do "without any"..
being the pressure from outside should push the two endcaps in place.
my2c
The external pressure was equal to the the entire craft so the ends and sides had the same tension. Titanium and carbon fiber have different expansion/contraction rates.
The craft was built in temperatures around 70 degrees F (21C) and went to the ocean probably 40 degrees F (4C)
Do 20+ dives without checking the bond. I say it was suspect.
From experience, I built a model helicopter in 1975 and glued a plywood bulkhead to the fuselage with epoxy. The plywood edges were sanded smooth and broke loose on the first flight. A seasoned pilot/builder told me never attach perfectly smooth parts like that. On the rebuild, I roughened the edges of the plywood and the attachment point of the fuselage and the glued part never came off.
Try to epoxy something to glass and see what happens.
Those titanium parts were 'shiny smooth' and fitted without any mechanical attachments.
the Titanium ends were not budging
hence popping off. That could be it or the window as you mentioned.
So, yes you're right (I just personally think the glue held).
Still my main concern is the fibers inability to withstand compression.
Anyhowsers. It sais a lot about the wildcat ceo
that he was willing to risk other peoples lives. So maybe we will see those lawsuits you were talking about against Ocean Gate after all, but will there be money left in the company. I guess not.
last comment for now: at least James Cameron went alone.
Carbon fibre has a density of 2000 kg/m3 and has poor comprehensive strength. Also due to the manufacturing method it would have poor shear strength.
Titanium has a density of 4500 kg/m3 and has poor tensile strength.
The omission of mechanical fixings was a problem.
All this probably led to unequal movement at the joints which would have led to microscopic separation and the ingress of water under pressure of 6000 psi. (Car wheels have 30psi)
For comparison a submarine's hull is all steel.
His sub wasn't built on a budget.
Mr.Rush was a dangerous man even if his dreams was sweet.
I see more videos on the Titan subject online daily.
The Coast Guard knew what had happened on the first day but were expected to wait until the craft was located.
this is really all I would need to know. I'da been like, ah, guys.....I think I'll pass.
Maybe that was the problem. Spaceships are designed to be in zero atmosphere...
The Titan assembly was only held together with glue and no mechanical fasteners.
It was done wet and no provision was made for the different cure rates between the inner wrap and outer wrap. Separation will occur with that type of manufacturing. What should have happened is doing the layup dry and the entire structure put into a chamber where the air gets pumped out and then filled with resin and catalyst. The entire wrap would be a continuous and solid cure without any air bubbles.
You have to click the link as 'hot linking' is blocked.