Autoclave

Question 1

In the bag molding process, what is the component that absorbs excess resin and
is usually made from a polyester mat or fiberglass coated with teflon or cotton.

Answer 1

Bleeder

Question 2

Why are high pressures used in the autoclave process?

Answer 2

To provide ply compaction and suppress void formation

Question 3

What is NOT a common defect of the bag molding process?

Answer 3

Common defects are: voids, improper cure, defects related to ply lay-up, defects
related to trimming operations, residual curing stresses, air, moisture, solvents
absorbed during manufacturing, foreign matter, filament crossovers

Question 4

Why is vacuum pressure applied at the start of the curing process?

Answer 4

Removes volatiles from flowing resin, helps create and maintain a positive
hydrostatic resin pressure to force deeper dissolved volatiles out before gelation.

Question 5

Why do voids occur?

Answer 5

Voids form due to trapped volatiles. A higher working temperature will increase
the volatile pressure. This translates to a void only if the volatile pressure is
higher than the hydrostatic resin pressure created by the vacuum and autoclave
pressure.

Question 6

For a two-stage cure cycle of a prepreg, what is used to indicate that the first stage
is done?

Answer 6

The first stage is done when the minimum resin viscosity is reached, which is
usually after one hour.

Question 7

Why is it common to dwell at temperatures lower than the cure temperature for a
two-stage cure cycle?

Answer 7

It allows lay-up to achieve a uniform temperature throughout the entire part, and it
allows resin to reach a low viscosity

Question 8

What factors dictate the resin flow for a lay-up?

Answer 8

Layup thickness, heating rate, pressure application rate.

Question 9

In a bag molding process, what is the point of having a barrier layer?

Answer 9

It limits the upward movement of resin and prevents resin from clogging the
breather and vacuum lines

Question 10

With a much larger autoclave containing multiple parts of varying sizes, what are
some issues that can occur?

Answer 10

Each part will require removal of vacuum at different times, which means the
needed autoclave pressure will vary for each part as well. Temperature hold times
will also be an issue.