Mechanical and thermal insulation properties of carbon fibre-reinforced carbon aerogel composites

Carbon fibre-reinforced carbon aerogel composites (C/CAs) were prepared by using polyacrylonitrile (PAN) and phenolic (PH) carbon precursor fibres as reinforcements, respectively, then impregnated with resorcinol-formaldehyde sol, aging, solvent exchanging, CO2 supercritical drying and carbonization at 1000°C. The physical properties, structural morphology and mechanical and thermal insulation behaviour of the two kinds of composites were further compared. Pore structure analysis shows that the PH-based C/CAs have a larger specific surface area (438.92 m2·g−1) and richer mesoporous volume than the PAN-based C/CAs. Mechanical behaviour of the C/CAs has been changed, but the stronger enhancement effects belong to PAN-based C/CAs (compressive strength in xy and z-directions are 1.63±0.10 MPa and 1.22±0.19 MPa, bending strength is 3.62±0.50 MPa). However, the PH-based C/CA composites have relatively low thermal conductivities, ranging from 0.027 to 0.164 W·m−1·K−1 between 25 and 1800°C.