Modification of Carbon-Fiber-Reinforced Composites to Mitigate Fiber-Lofting in Burning

摘要

Two lines of investigation have been undertaken to attack the problem of fiber-lofting when carbon-fiber-reinforced composites are subjected to fire or incineration. The objective is to find means to retain the fibers within the matrix char and thus prevent their release before they are destroyed by oxidation. The first investigation employs a chemical approach based on experience with ablation-resistant matrix polymers and seeks to enhance fiber retention by blending high-char-yield polymers into conventional matrix systems. A concurrent microstructural approach includes direct observations of the processes of burning and fiber-lofting and thus seeks to understand the mechanisms by which fibers are released or retained by a composite under fire conditions. The investigations of matrix blending have focused on hybrid resin systems consisting of polyphenylacetylene (PAC) or polyphenylquinoxaline (PPQ) additions to conventional epoxy novolac resins. Stable and compatible blends have been prepared by selection of suitable solvents. Thermogravimetric analyses show that both char yield in vacuum and the temperature range for oxidation by air are substantially increased by blending. No serious difficulties were encountered in preparing unidirectional composites with the blended resins.