Development and fabrication of graphite polyimide launch vehicle structures

Composite materials containing graphite or boron fibers in epoxy matrices have satisfactory strength characteristics only at temperatures not exceeding 250 F. Because of this limitation, a combined materials, manufacturing, design, and analysis program was launched to pursue the development of a graphite fiber/resin matrix composite for use at above 600 F, taking into account potential applications for launch vehicle upper stage structures. The results of the first studies of the program left only the addition polyimides for further consideration. It was found that both PMR-15 and LARC-160 had the potential to meet the program objectives. Attention is given to cure cycle development of graphite cloth/PMR-15 polyimide and graphite cloth/LARC-160 polyimide, the rationale for utilizing internally heated tooling for graphite/addition polyimide composites, and the fabrication of the cylinder.