Effect of fiber weight fraction on mechanical properties of carbon–carbon composites

This article presents the synthesis of carbon–carbon (C/C) composites by preformed yarn (PY) method, by varying the percentage of carbon fiber weight fraction. The PY used was carbon fiber bundle surrounded by coke and pitch which was enclosed in nylon-6. Three types of samples with fiber weight fractions of 30, 40, and 50%, respectively, are fabricated and mechanical properties were studied. In each case, the PY was chopped and filled into a die of required shape and hot pressed at 500°C to get the preform composite. To obtain the carbonized and graphitic structure, the specimen was heat treated at 2500°C followed by soaking for 10 to 12 hrs. Further, two cycles pitch impregnation was done by hot isostatic pressing, to eliminate the voids and to increase the density hence to obtain good mechanical properties. The characteristics such as hardness, flexural strength, and impact strengths were studied. It is observed that, as the carbon fiber percentage increases, the properties also get improved, provided sintering is done at fairly higher temperatures such as 2700°C. The superiority of the new class of C/C composites made by the proposed PY technique over those obtained by the conventional methods is also demonstrated. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers