Process Optimization of Needled Carbon/ silica carbide (C/SiC) Structural Insulators

Some missiles employ a throttleable divert and altitude control system (TDACS) to maneuver the kill vehicle to the target. Hot gas valve components in the TDACS must survive long burn times at high pressures and high temperatures. Recently the team of Materials Research & Design (MR&D), Allcomp, and Southern Research Institute (SoRI) has developed a needled C/SiC composite that exhibits strengths that are equivalent to Novoltex (the present TDACS material) and less conductive than Novoltex. The composite is fabricated with commercial needled brake preforms, a commercial pre-ceramic polymer, and a unique heat treatment cycle that maintains strength while reducing conductivity. Aerojet tests of the new material (identified as 16A) resulted in five of six successful rocket motor firings. The failure was due to a broken pintle that was traced back to poor Z fiber distribution in the commercial brake (Gen 4) preform. The recently completed Phase I program addressed the composite failure by fabricating and characterizing C/SiC composites made with Allcomps recently developed, domestically available, needled carbon fiber preform (Gen 7). The Phase I data showed 16A composites from Gen 7 preforms led to thermal conductivities, Z tensile strengths, and inplane flex strengths that were equal to or better than those from Gen 4 preforms. Furthermore, C/SiC composites using improved Allcomp preforms (Gen 8) have performed very well in recent, more aggressive, Aerojet-funded rocket motor tests. The objectives of the proposed Phase II are 1) to continue the development of 16A composites using the new Allcomp needled preforms (Gen 8 or 9), and 2) transition the composites to future TDACS hardware. The low thermal conductivity and high strength of the 16A material translate directly into smaller valve hardware, more compact motors, and longer burn times. The Phase II program will be performed by the team of MR&D, Allcomp, SoRI, and Aerojet. MR&D will design and analyze hardware for ground test evaluation, Allcomp will fabricate the materials, SoRI will develop a property database to support the design, and Aerojet will guide the material development and perform rocket motor tests. Approved for Public Release 15-MDA-8169 (20 March 15)