Strength retention of fire resistant aluminosilicate-carbon composites under wet-dry conditions

The results of an experimental investigation of the durability of inorganic matrix-carbon composites are reported. The matrix, which can sustain temperatures up to 1000°C, is being evaluated for applications that require fire resistance, such as the interior of aircraft. The original matrix formulation, which had a high ratio of silica to alumina, was found to weaken when subjected to wet-dry cycles. Preliminary tests indicated that an efficient way to increase water-stability was to increase the amount of alumina in the matrix. Therefore, a systematic evaluation was carried out to obtain the optimum silica/alumina ratio for improving stability of composites in water. In-plane shear strengths were used as an indicator of strength retention after the specimens were subjected to 50 wet-dry cycles. The results indicate that silica/alumina ratio between 18 and 20 provide the best results. In this range, strength loss is negligible.