Pressure vs Vacuum Compaction

[carbondude]

Good Morning All!

Which method is superior for carbon fiber Pre-Preg Compaction?

1. Pressure bladder against steel mold

or

2. Vacuum bag against steel mold

Note: The steel mold contains some fine details, I really need
the pre-preg to get forced into the corners.

Thanks!

 

[SWComposites]

Are you talking about compaction during layup or cure?

What pressure level with the bladder?

"Forcing" material into interior corners is often problematic and requires use of pressure intensifiers during cure.

"Better" (or "sufficient") is often highly dependent on the particular mold shape, material, cure temperature, etc; manufacturing process trials are highly recommended.

 

[berkshire]

Carbon dude,
You need to explain your proposed method a little better.

Are you using pressure in a non autoclave use with direct heating of the mold?

A vacuum bag will only give you whatever the atmospheric pressure of the day is, if you can pull a full vacuum.
If you put the bagged product into an auto clave you can add whatever pressure the autoclave can produce. Somehow I do not think you are doing this.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[carbondude]

Hi Folks,

Thanks for the questions...

This would be an autoclave heated mold application.

Consider (just for comparison) 150 psi pressure

vs bell jar levels of vacuum.

Just wondering which is more effective at compacting the pre-preg,

especially into square corners.

Thanks Again!

 

[SWComposites]

More pressure = "better". Is it enough?, maybe, maybe not. Is it overkill? maybe, maybe not. Depends on many details which you have not defined.

Compacting into "square corners"?? really? why? use a generous radii and greatly reduce your potential problems.

 

[berkshire]

If you are worried about compacting the pre preg into corners, you can while you are pulling your vacuum, take a smooth paddle and push the the prepreg into the corners. Do it slowly and gently so you do not push a hole in the bag.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[carbondude]

Thank You All For Your Answers.

Cheers!