| Rayon/SC-1008 fiber-based composite materials have been used successfully to line the inner surface of ablative nozzles. But Rayon is no longer produced locally in the United States, primarily due to environmental considerations. The material is available from suppliers located overseas but, for military purposes, there is a pressing need to eliminate foreign dependence.;The primary objective of this dissertation is to find a suitable replacement for the Rayon composites currently used in ablative nozzle applications. Other researchers tried to do this by using a composite system consisting of PAN fiber cured with a phenolic resin (91LD). But micro-cracking occurred in the cured resin due to moisture loss over time. The progressive moisture loss, and subsequent shrinkage of the material, induced residual stresses that ultimately resulted in delamination as the material desiccated.;PAN fiber was selected to reinforce the composite system in this dissertation because it mimics the structural behavior of Rayon fiber and is readily available from manufacturers located in the United States. The main challenge was to find a matrix material that could cure the PAN fibers into a composite system that would perform equal to, or better than, its Rayon counterpart.;Three different resins (SC-1008, PETI-5 and CelazoleRTM) were selected for the matrix based on recommendations found in the literature. Although the majority of applications associated with Rayon rely on the use of pre-impregnated materials, comparisons were made herein using wet hand lay-ups, simply because the PAN composites targeted for study were not readily available in a pre-impregnated form.;A Rayon composite panel was fabricated to serve as a baseline. The performance of other material candidates was compared to that of the baseline using: a micro-crack study conducted with photomicrography, thermal gravimetric analysis (TGA), residual volatile (RV) loss measurements, and a thermal mechanical analysis (TMA). Material candidates were ranked relative to the baseline regarding performance, cost and manufacturability.;Results show that a PAN/SC-1008 constituent/matrix can be manufactured that meets or exceeds the characteristics of the Rayon-based constituent/matrix; thereby establishing a new source of composite materials for ablative nozzle fabrication and/or military applications. |
