OutofAutoclave

Out of autoclave (OoA) refers to resin-based composite manufacturing processes that cure or harden without using an autoclave to apply heat and pressure. In OoA, components are typically formed from dry fabric or prepregs laid into a mold and consolidated using vacuum bagging, with resin introduced through infusion or injection. Pressure is generated primarily by vacuum rather than by a pressurized autoclave chamber, and curing often occurs in an oven or heated enclosure.

Common OoA techniques include vacuum-assisted resin transfer molding (VARTM), resin infusion, and various open- or closed-mold infusion methods. In many cases, resin is drawn through a preform by a vacuum to achieve fiber wet-out and compaction. The setup usually employs layers such as peel ply, bleeder fabric, and breather to control resin flow, air removal, and surface finish. While some OoA processes can produce parts with good surface quality and sufficient strength, achieving high fiber volume fractions and very low void content typically remains more challenging than in autoclave-cured parts.

Materials and applications vary, but epoxy resins with carbon, glass, or other fibers are common. OoA approaches are widely used in aerospace components, automotive parts, wind turbine blades, marine structures, and sporting goods where lower capital costs, simpler tooling, and the ability to manufacture larger or more complex shapes are advantageous.

Advantages of OoA include lower equipment and tooling costs, reduced energy use, and flexibility for on-site or field manufacturing. Limitations commonly cited are lower potential fiber volume fractions, higher variability in void content, and greater sensitivity to process conditions, which can affect mechanical performance and repeatability. Ongoing research aims to improve process control, resin systems, and tooling to close the gap with autoclave performance.