Caulk between Composite tube (150mm) & Steel Cap; any idea?

Caulk between Composite tube (150mm) & Steel Cap
Liquid contain: Water, Applied pressure 200 Bar (approximately)
Do you think the caulk will works, can you direct me if you had an experience about similar jobs, can I calculate this caulk rate and reliability via handy calculations or with related analyzer software’s (It’s Name please?)
This is a concept model just for question clarifying

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I would think that o-rings rather than caulk is the way to go. Remember caulk needs to set up and it would be difficult to know when it does and to predict the properties when it does. In contrast O-rings are already set and the pressures that it can hold should be predictable as they are published. The end seal might do most of the sealing. If not the side o-rings will supplement.

In the end I suppose you will have to do some verification to prove your concept.

Good luck.
Dear Vincente;
Hello;
Thank you for your reply, finding an engineering way to predict the caulk reliability is my purpose at this discussion, I know that i can find the best way by using experimental methods, but as you know this can spend a few money and time! so i want to find an engineering solution for that before i forced to test it at manufacturing
plus please attend to the pressure it is 200 bar it is high pressure and it must cause to the tube gone to crash, do you think the seal will work at this condition? can you suggest a good set up and O ring property for this assembly please?
thanks again
I am not sure you will be able to ensure an air tight seal if you are sliding the cap over the tube. But, lets assume you will be able to get the proper distribution of material and a controlled caulk application and assembly process to accomplish this.
You will need to consider both the cohesive and adhesive properties of the caulk you intend to use. The bond strength to both substrates is a value that can be tested and general values should be readily available from the manufacturer. The cohesive strength is a little trickier, but you should also be able to derive the information from the technical data such as tensile strength.
There are a wide variety of materials that you can use, both 1 and 2 part. If air flow is restricted to the caulking, it is probably best to use a 2 part to eliminate the need for air flow. Many caulks require the presence of atmospheric moisture or must flash off a solvent. If you intend to bond the cap to the tube, as you would likely need to to accomplish this, you might be better served by an epoxy or methacrylate compound.

Good luck,

Tony
Hello Ali-

Perhaps you already have a solution by now but, just in-case here's what we have done in the past.

....We tend to have a steel part integrated into the carbon fiber inorder to produce steel on steel contact for your o-rings. The steel cap can be wound up during the carbon fiber process (assuming you are winding here and not manually laying up). That being said, we leave a little extra material (.060) for a clean up pass on the lathe to ensure a nice sealing surface and to meet tight tolerances requiremnets typically seen in o-ring applications.
Hello;
Thank you for your reply;
As you noted the tube produced by filament winding and after wound up it’s finished by lathing and now you add another process! Yes its better that we leave extra epoxy resins at the ends of the tubes so we can have an extreme finished surface by grinding of two ends of the tubes!
Thank you for your idea


Javier said:
Hello Ali-

Perhaps you already have a solution by now but, just in-case here's what we have done in the past.

....We tend to have a steel part integrated into the carbon fiber inorder to produce steel on steel contact for your o-rings. The steel cap can be wound up during the carbon fiber process (assuming you are winding here and not manually laying up). That being said, we leave a little extra material (.060) for a clean up pass on the lathe to ensure a nice sealing surface and to meet tight tolerances requiremnets typically seen in o-ring applications.
Dear Tony
Hello;
We have water with high pressure (200 bar) at this assembly if test prepared to run the caps must be fixed at the positions but as you know we can’t apply more power at the axial and radial directions because the composite tubes can’t carry out Load at the axial direction plus we can’t apply more power at the outer surface of the tube (from out of cylinder to the center) but reverse is available (from center to the out) its design need strength at this direction.
Recently I figure out that none of o-rings and packing’s can’t use at this pressure!!
Can you tell me more about the other materials that available for sealing purposes (Non adhesive &cohesive) that can be shaped as a seal by lathing or other ways that maybe you know?
You can see the last sealing property at below:


you can see pressure distribution that can deform the sael from center to out below:


A nonlinear analysis on rubber material show that the seal can deform 14.5~17.5 mm along its diameter


Tony OConnell said:
I am not sure you will be able to ensure an air tight seal if you are sliding the cap over the tube. But, lets assume you will be able to get the proper distribution of material and a controlled caulk application and assembly process to accomplish this.
You will need to consider both the cohesive and adhesive properties of the caulk you intend to use. The bond strength to both substrates is a value that can be tested and general values should be readily available from the manufacturer. The cohesive strength is a little trickier, but you should also be able to derive the information from the technical data such as tensile strength.
There are a wide variety of materials that you can use, both 1 and 2 part. If air flow is restricted to the caulking, it is probably best to use a 2 part to eliminate the need for air flow. Many caulks require the presence of atmospheric moisture or must flash off a solvent. If you intend to bond the cap to the tube, as you would likely need to to accomplish this, you might be better served by an epoxy or methacrylate compound.

Good luck,

Tony
this Concept is okey, but it may have Radial force to cap at the end of it ( on the sealed place). If I were you, I'd clamp the upper and beneath caps together. like Hydraulic cylinders. 3 ones are enough.
Composite pressure vessels are available for H2 vehicle manufacturers and should reduce your set up time.
One problem with composite/metal construction is corrosion when the two are in contact in a damp environment.
The ready made units are practically indestructable and corrosion resistant. I will include a video that describes their use in a Hydrogen vehicle the strengths and distributor.

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