Effect of punching density on the mechanical and thermal properties of needle-punched nonwoven carbon/phenolic composites

The effects of changes in the fibre orientation on the mechanical properties of nonwoven composites were investigated through 3-point bending, short beam shear and tensile tests. Oxidized polyacrylonitrile(PAN) carded webs were needle-punched, and then carbonized to fabricate carbon composites with phenolic resin. The interlaminar shear, tensile and flexural strengths increased with increasing punching density. However, the rate of increase reduced and interlaminar shear and tensile strengths decreased with excessive punching density. The erosion rate and the insulation index were calculated by means of a torch test. The ablation resistance increased with increasing punching density, but no significant increase in the erosion rate with increasing punching density above 477 penetrations per square centimetre was found. The thermal conductivity of needle-punched nonwoven carbon/phenolic composites increased with increasing punching density.