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Vacuum-Bagging Supplies |
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Hah. Thought so.
A properly vacuum-bagged part will be lighter and stronger for two reasons. First, there will be fewer air pockets in the laminate. Air pockets (bubbles) are weak areas that can compromise the strength of that part. Second, a vacuum-bagged part will have a more controlled amount of resin.
Although resin serves a purpose (to wet out the fabric and help it conform to the mold shape), too much is definitely not a good thing. Vacuum-Bagging helps the user control the percentage of resin in the part so that the intended strengths are what are actually achieved.
HOW DOES VACUUM-BAGGING WORK?
It works because removing the air from one side of a hermetically sealed space takes away the equilibrium. Now, you've got pressure on one side only. Ergo, it works.
Somebody's gonna whine now. Pressure? Vacuum is expressed not in pounds of force, but in inches of mercury!! Yeah yeah yeah we know. BUT, at sea level, atmospheric pressure is 14.7 psi, right? Remove the atmosphere and what do you get? 14.7 psi of pressure from the atmosphere, unopposed as it squeezes the ever-lovin' devil out of that laminate.
Test question. What's the equivalent weight (in pounds) that would be applied to an area of one square foot if we were using a vacuum bag to evacuate the air over that area? Assume sea level and atmospheric pressure of 14.7 psi.
FILM AT 11. |
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| Vacuum-Bagging Film |
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| This is the last film that is applied when constructing the vacuum-bag. Its primary function is to be free of leaks and be able to hold vacuum under intended pressures and temperatures. |
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| Release Film |
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| This film is often made of some variety, cousin, or neighbor of the Teflon family. It's non-stick, usually temperature resistant, and can also be permeable so that in spite of its solid appearance, it still breathes. Cool, huh? |
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| Breather Fabric |
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This is the transporter mechanism for the air you're trying to suck out of the laminate. As the vacuum builds, the air needs a way to get out.
The breather (sometimes called a bleeder) provides a passage for said air. Ok, technical term here. Ready? "GASES". |
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| Bag Sealant Tape |
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| This is the tape (looks like butyl tape for windows) that is used to provide a seal between the vacuum-bagging film and the tool or mold surface. |
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| Peel Ply Fabric |
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| Peel Ply (Also known as Release Fabric) is used to provide a cured composite laminate with a textured surface. This helps if you are bonding one part to another, or if you just want paint to stick a little better. |
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| Pressure-Sensitive Tape |
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| Here's the polyester flash tape, the PTFE with the glue on one side, and other tape goodies that make a composites house a composites home. |
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Vacuum-Bagging Supplies |
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