VACUUM BAG ONLY PROCESSING; IMPROVING PREPREG OUT-TIME AND POROSITY FOR LARGE COMPOSITE STRUCTURE

摘要

Composite materials allow aircraft manufacturers to design large unitized structures that reduce part and fastener count. Though these materials provide a significant weight advantage as compared to metal, they tend to be more expensive to process because of costly tooling, required large autoclaves and supporting infrastructure. To address these drawbacks, the industry is increasingly adopting out-of-autoclave (OOA) processing methods. These methods eliminate the need for autoclaves, reducing overhead and capital costs and allowing production of very large structures. The most versatile of the OOA processes is vacuum bag only (VBO) processing. Materials manufacturers face several challenges in developing prepregs for VBO processing. Materials must have long tack-life and out-life to allow time for lay-up and bagging of very large complex structures. Materials must also be formulated to achieve primary structure performance levels with acceptably low porosity in the absence of the consolidation pressure provided by autoclave curing. This paper discusses the challenges of developing VBO materials with emphasis on out-time extension and porosity reduction. Performance of two OOA material systems is presented in relation to a proven primary-structure-capable, autoclave-cured material system.