Correlation between the Surface Energetics of Reinforcement and Mechanical Properties of Carbon/Carbon Composites

Surface energetics of reinforcement is one of the most important properties in case of adhesion of reinforcement in composites . For this study, PAN fibres were stabilized isothermally with three different timings (viz. 0, 1, 2 h) and eventually prepared fibres having different surface energetics were evaluated by DCA 322. Composites
were made by using these stabilized fibres (designated as OP, 1 P, and 2P) with coal tar pitch as matrix precursor using match mould die technique. Green composites
were carbonized upto 1000°C, then impregnated and heat treated to 1500, 2000 and 2600°C. Green composites as well as heat treated composites were studied for their
mechanical properties . Microstructure as well as interfacial studies were carried out using optical microscope.
Optical microscopic examination of composite samples show that Ill treated fibres offer much better adhesion with matrix precursor and the matrix also exhibits
an obvious increase in the anisotropic domain size in case of 2P composites . Density of stabilized fibres and also of green composites has been found to increase with
stabilization time. Flexural strength of green composites prepared with 0 and 2h treated fibres decreases ( 123 MPa to 60 MPa). However, as a result of better bonding between
fibre and matrix , in case of IP composites , strength is always high except in green stage . An attempt has been made to correlate the surface energetics of fibre with
mechanical properties as well as matrix microstructure of carbon /carbon composites.