Monitoring unidirectional carbon/carbon composite processing by light microscopy

Unidirectional carbon/carbon composites were prepared using polyacrylonitri le-based carbon fibres and a commercial coal-tar pitch, The preparation inc ludes a three-sequential-step process: (i) prepreging, (ii) moulding/pressi ng, and (iii) carbonization to 1000 degreesC, The effect of the process par ameters including pressure, mould characteristics, and temperature and dura tion of pressure application on the microstructure of composites was monito red by light microscopy. Results show that the application of a pressure of 1 MPa close to the temperature of pitch solidification produces lower poro sity composites. This porosity is significantly reduced when the solidifica tion of the pitch is tempered by the introduction of a soak time of 10 h at the temperature at which pressure is applied.