Effect of needle-punched preform parameters on the mechanical properties of carbon/carbon composites

Carbon fiber preforms were prepared and then densified to produce carbon/carbon composites using needle-punching and chemical vapor infiltration technique, respectively. The effects of the preform manufacturing parameters, including the needle-punched density and its depth, and the mass-to-area (M/A) ratio of short-cut fiber felt, on the mechanical properties of the composites were investigated. The relation between the mechanical properties of the composites and the bulk density of the preforms was also discussed.Results show that the tensile strength of the composites increase and thereafter decrease as the needle-punched density increased from 20 to 50 pin/cm², while the interlaminar shear strength of the composites tends to increase. The tensile and interlaminar shear strengths exhibit an increasing tendency with the increase of needle-punched depth from 10 to 16 mm, whereas they reduce as the M/A ratio of short-cut fiber felt is increased from 100 to 300 g/m².Both the tensile and interlaminar shear strengths are dominated by the preform density when only one parameter of the needle-punched density and its depth, and the M/A ratio was varied. The preform density could be employed as a key macro-parameter to predict the mechanical properties of the composites.