A comparison of the interfacial, thermal, and ablative properties between spun and filament yarn type carbon fabric/phenolic composites

In the present paper, the interfacial, thermal, and ablative properties of phenolic composites reinforced with spun yarn type carbon fabrics (spun UP composite) and filament yarn type carbon fabrics (filament C/P composite) heat-treated at 1100 degreesC have been extensively compared. The interlaminar shear strength, crack growth rate, and fracture surface were studied to evaluate the interfacial characteristics of the composites using short-beam shear test, double cantilever beam test, and scanning electron microscopy, respectively. The thermal conductivity and the coefficient of thermal expansion were also measured in the longitudinal and transverse directions, respectively. To explore the ablative characteristics of the composites in terms of insulation index, erosion rate, and microscopic pattern of ablation, an arc plasma torch was used. The interfacial properties of the spun C/P composite are significantly greater than those of the filament C/P composite, with qualitative support of fracture surface observations. It has been investigated that the presence of protruded fibers in the phenolic matrix of the spun C/P composite may play an important role in enhancing the properties due to a fiber bridging effect. The longitudinal thermal conductivity of the spun C/P composite is about 7% lower than that of the filament C/P counterpart. It has been found from the ablation test using arc plasma torch flame that the erosion rate is 14% higher than that of the filament C/P counterpart. Consequently, all the experimental results suggest that use of spun yarn type carbon fabrics heat-treated at low carbonization temperature as reinforcement in a phenolic composite may significantly contribute to improving the interfacial, thermal, and ablative properties of C/P composites. (C) 2004 Elsevier Ltd. All rights reserved.