[1] OOA curing achieves the desired fiber content and elimination of voids by placing the layup within a closed mold and applying vacuum, pressure, and heat by means other than an autoclave.
With these qualities, composite materials are gaining wide use in a variety of structural and non-structural applications common in aerospace and aviation.
What sets SQRTM apart from standard resin transfer molding is the substitution of a prepreg layup rather than a dry fiber preform.
The prepreg is placed in a closed mold and during the cure cycle, a small amount of resin is injected into the cavity through ports positioned around the part.
[4] The key factors in the SQRTM process include precision machined closed mold tooling, high pressure presses, a high vacuum applied to the tool interior, and precise control of heating platens, injected resin volume, heat, and pressure.
[citation needed] The advantages of the SQRTM process include a high level of integration, tight tolerances and the use of qualified prepregs.
Liquid resin is introduced through ports in the mold and vacuum-drawn through the reinforcements by way of designed-in channels and infusion media that facilitate fiber wetout.
The process's comparatively low-cost tooling allows inexpensive production of large, complex parts in one shot,[1] such as the tail of the Mitsubishi SpaceJet.
The part, typically under full vacuum, is subject to pressures as high as 250kPa fluid pressure and can be rapidly heated to the desired cure temperature without risk of catastrophic exothermic reaction, as the HTF can draw excess heat as desired.
The use of fluid to control temperature, as opposed to the gas generally used within methods such as autoclave and oven curing equates to lower energy consumption, faster cycle times and extremely accurate part temperature control.
Another out of autoclave method for achieving external compression on prepreg based composite parts is through the use of heat shrink tape.