An autoclave is a hermetically sealed enclosure for curing composite materials, in which thermal and pressure cycles can be simultaneously applied and controlled.
The heat is transferred through the internal fluid (air or nitrogen), and the heating can be programmed allowing precise thermal cycles to be applied (temperature rises, flat segments and cooling). The temperature is often continuously controlled at several points to ensure good temperature consistency (it can reach 400°C).
Pressurising uses a filling fluid and is also programmable and combined with the thermal cycle to ensure that pressure (between 2 and 50 bars) is applied at the appropriate times.
The enclosure is placed under vacuum in the same way as for a component polymerised in an oven, using a vacuum pump. This is also programmed and controlled by the autoclave controller.
The autoclave, with its precisely controlled and fully repeatable temperature/pressure cycle, makes it possible to produce well compacted components.
This equipment is costly and is only used for high performance composites.