Out-of-autoclave processing and properties of bismaleimide composites

Abstract

*This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States. The emergence of bismaleimide composites has fulfilled some of the increasing demand for higher temperature performance aeronautics and space exploration vehicles. This study examines and evaluates three bismaleimide matrix resins and two bismaleimide adhesives and reports on the processing properties of these resins and composites by out-of-autoclave–vacuum-bag-only oven processing. Measurements were conducted under various cure cycles to characterize and correlate thermal and viscoelastic properties of the materials. Specimens of all three aged matrix resins exhibited an out-time life up to 30 days when stored at room temperature. Solid and sandwich panels were fabricated with the out-of-autoclave–vacuum-bag-only process. Because of tooling limitations in industry practices, composite fabrication of these bismaleimides was restricted to a maximum 177℃ curing, followed by a free-standing postcuring at elevated temperatures in an oven. The adhesive foaming characteristics, composite resin/void content, flat wise tensile strength, and fracture surface features were evaluated. Due to the unique temperature limitations of this work, the resulting panel properties were not necessarily representative of manufacturer specifications or recommendations.