Abstract
The objectives of this study are utilizing thermoplastic polymer (poly(ethylene oxide, PEO)) to modify Novolac type phenolic resin and to prepare carbon/carbon composites.Different ratios of PEO were added to the Novolac type phenolic resin to fabricate carbon/carbon composites and to investigate the microstructure of carbon matrix of phenolic resin and the interface between resin matrix and carbon fiber. The mechanical properties (density, porosity, flexural strength and interlaminar shear strength), physical properties (toughness behavior, internal pressure build up) and degradation kinetic parameter (activation energy, frequency factor) of the composites before and after carbonization were studied.The wet-out between the carbon fiber and the matrix of the PEO modified novolac type phenolic resin after SEM photographs investigated curing. Apparently, the interfacial bonding between carbon fiber and resin matrix was improved significantly with the increasing of PEO content.The flexural strength of carbon/carbon composites precursor with 5 phr ( part per hundred parts of resin) PEO is 10﹪higher than that of specimen of neat phenolic resin. However, the density and the porosity do not change significantly. The flexural strength of carbon/carbon composites with 10 phr PEO is 40﹪ higher than that of specimen of neat phenolic resin. Although the density was decreased，the porosity was increased for carbon/carbon composites containing PEO. The existence of PEO will help to reduce the internal stress build-up and to enhance the flexural strength of the fabricated carbon/carbon composites.The interlaminar shear strength (ILSS) of carbon/carbon composites precursor with 10 phr PEO is 40﹪ higher than that of specimen of neat phenolic resin. PEO was added to improve the interfacial bonding between the matrix and the fiber. The interlaminar shear strength of carbon/carbon composites with 10 phr PEO is 10﹪higher than that of specimen of neat phenolic resin.The flexural strength and the density of the 2-D carbon/carbon composites densified via liquid resin reimpregnation process were increased with reimpregnation times. The flexural strength of carbon/carbon composites through four times densification process is 90﹪ higher than that of the undensified neat phenolic resin . The flexural strength of carbon/carbon composites with four times densification process is 18﹪higher than the undensified 10 phr PEO/phenolic resin system.For degradation kinetic parameter of PEO/phenolic resin system, thermoplastic polymer can reduce the maximum degradation temperature of phenolic resin with the increasing PEO content. The maximum weight loss by degradation also was increased with PEO content.