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I have seen plenty of YouTube videos in which they use carbon fiber fabric to build various things. One such channel is Mike's Patey's channel where he makes amazing aircrafts from carbon fiber.

In these videos I usually see (but not always) that after they apply the resin to the fiber fabric, they put the structure in a kind of plastic bag and they vacuum pump it.

Why is that process? Is it hardening and giving some extra rigidity to the fiber in any way? Can this process be done by the use of pressure? (eg. a kind of mold that pressurizes the fiber from the outside so that the fiber also takes the correct shape).

Efthymios Kalyviotis
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2 Answers2

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Solar Mike's answer is accurate.

Carbon fiber has a resin to fiber ratio which provides the optimum strength. This is typically measured by weight. The amount of resin is applied to the fiber prior to enclosing it for vacuum application.

Once the vacuum begins, all of the air is removed from the fiber, forcing the resin into the voids, ensuring the strength aspect.

The pressure aspect will not remove the air from the enclosure containing the fiber. The voids within are going to be smaller but not non-existent. Another reason for vacuum bagging as a system is that it is not restricted to any specific container. Sufficient plastic and sealing will allow fiber constructions of immense size.

fred_dot_u
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There are two reasons:

One is to remove trapped air bubbles

and

two to pack the fibres as densely as possible within the structure or weave of the fibre pattern wanted.

Solar Mike
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