Sealing carbon fiber tubes for deep water application
Sealing carbon fiber tubes for deep water application
(OP)
Hello,
I'm looking for an effective way to seal a carbon fiber tube with a plastic (probably Delrin) end cap and o-ring. The tube houses electronics and is used in a deepwater application. I'm from a machine design background and would normally have a retaining feature (i.e.step or groove) machined in the tube ID if I were dealing with metal. I don't have much experience with composites and have concerns that machining will compromise the fiber layup and overall compression strength. Anyone know if this has been done with success, or if there are other effective options (I'm thinking adhesives/expansion insert/compression fit).
Thks
I'm looking for an effective way to seal a carbon fiber tube with a plastic (probably Delrin) end cap and o-ring. The tube houses electronics and is used in a deepwater application. I'm from a machine design background and would normally have a retaining feature (i.e.step or groove) machined in the tube ID if I were dealing with metal. I don't have much experience with composites and have concerns that machining will compromise the fiber layup and overall compression strength. Anyone know if this has been done with success, or if there are other effective options (I'm thinking adhesives/expansion insert/compression fit).
Thks





RE: Sealing carbon fiber tubes for deep water application
RE: Sealing carbon fiber tubes for deep water application
RE: Sealing carbon fiber tubes for deep water application
There are some great adhesives out there these days: GE, 3M, and many others. If you can glue it, that is probably the way to go. Machining the end is likely a very bad option.
RE: Sealing carbon fiber tubes for deep water application
Obviously there are high external pressure loads to be resolved as well. That is a separate issue impacting the tube structural design.
Thanks for your input. I'll look into the adhesive options.
RE: Sealing carbon fiber tubes for deep water application
If you're intent on machining stuff, then padding up the tube OD with sacrifical material should permit the machining of features (e.g. your O-ring groove) into the sacrificial plies. This could then be resin coated or metal plated to give a good seal surface. This might be appropriate if you're just tooling the inside.
Another option might be to shrink or bond on a metallic ring with the groove in it.
Depends a bit on what your tooling options are to make the tube. (Will you tool the inside or the outside or both?)
You will presumably be critical for circumferential E and strength; however, bear in mind that the groove could give a significant stress concentration for the axial compression stress, even if it's in a sacrificial ply build up.
RE: Sealing carbon fiber tubes for deep water application
RE: Sealing carbon fiber tubes for deep water application
Garland
Former marine engineer turned aero-engineering manager
RE: Sealing carbon fiber tubes for deep water application
..But the route I'm leaning towards now is to cut o-ring grooves in our end cap then press/shrink fit this in the tube ID with a lap joint and recommended adhesive.
I am a bit concerned about the comments about CF porosity though. Are there any grades of CF which are impervious to sea water?
Paul
Mechanical Design Engineer
Marine Electronics Packaging
RE: Sealing carbon fiber tubes for deep water application
RE: Sealing carbon fiber tubes for deep water application
RE: Sealing carbon fiber tubes for deep water application