The Behavior of Acid Treating Carbon Fiber and the Mechanical Properties and Thermal Conductivity of Phenolic Resin Matrix Composites

The oxidation of carbon fiber (OCF) was studied by HNO3/H2SO4 oxidation treatment, and the OCF reinforced phenolic resin (PR) matrix (OCF/PR) composites were prepared. The OCF was characterized by FTIR and Raman analysis. The results showed that OCF could effectively introduce the -OH and -C=O groups to the surface of carbon fiber, and increased the disorder of the carbon fiber surface. Different amount of OCF was incorporated into the PR matrix, and OCF/PR composite was characterized by scanning electron microscopy (SEM), impact tests, flexural tests and thermal conductivity analysis in detail. SEM images showed that the surface of roughness and area of carbon fiber after oxidation was increased. The results showed that the mechanical properties of carbon fiber after oxidation were better than raw carbon fiber reinforced of phenolic resin matrix composite. Compared to CF/PR composite, when the OCF was 0.4 wt%, the impact strength (flexural strength) of OCF/PR composites increased from 52.0 kJ/m(2) to 85.2 kJ/m(2) (from 220.2 MPa to 402.1 MPa), which increased by 63.8% (82.6%). In addition, compared to CF/PR composite, the OCF/PR nanocomposite had a higher thermal conductivity property at the same test temperature.