Relations between Needling Processing Parameters and Tensile Strength of C/C Composites

The experiments for the fabrication of needling preform were designed according to response surface methodology (RSM) by the design-expert software to study effects of three variable needling processing parameters on the tensile strength of carbon/carbon (C/C) composites. Mathematical model between needling processing parameters and tensile strength of C/C composites was set up to optimize the needling processing parameters of preform and to predict the tensile strength of C/C composites. The mathematical model has good fitting degree with P-value of 0.0206 and the relative error between the predicted and the actual is no more than 10.82%. Based on the analysis of response surface of tensile strength, the needling depth has very significant influence and the needling density has significant influence on the tensile strength of C/C composites. The predicted scope of the tensile strength by the mathematical model is from 42.31 MPa to 91.87 MPa. The calculated optimal values are tensile strength 88.62 MPa, needling density 11 pin/cm², needling depth 11 mm, and density of non-woven 50 g/m², while the corresponding experimental result is 90.71 MPa with relative error 2.36%.