Analysis of relationship between properties and behaviour of materials used and impregnation conditions of carbon–carbon composites

Relationship between material properties and impregnation conditions is analyzed and discussed. The porous structure in carbon–carbon composites was characterized by using optical microscopy and mercury porosimetry. Pores, voids and cracks in composites were divided into three groups according to the shape and into five groups according to the size. Two main models, cylindrical and plate, were used for the description of the composite porous structure. Rheological properties of liquid precursor and its dependence on impregnation conditions were measured by viscosimetry. Material balance of matrix precursor was calculated in order to determine filling of the pores after the whole impregnation–curing–carbonization cycle. Assuming Newtonian behaviour of liquid precursor, the relationship between properties of the materials used and the given conditions were discussed for the two pore models mentioned above. It was confirmed that external pressure effectively improves the impregnation of macro-pores while micro-pores are filled only by capillary pressure.