Thermal conductivity enhancement of vertically aligned nanotube carpet reinforced thermoset composites
Résumé
Fiber reinforced thermoset materials are more and more used for satellite structure manufacturing. Beside their in plane structural properties, advanced designs are requiring increased thermal and electrical conductivity, as well as damage tolerance against meteoritic impact. The main material weak point is related to the low properties of the interply polymer matrix. In order to enhance these properties, carpet like vertically aligned carbon nanotubes (VACNT) are investigated as reinforcing solution of the thermoset resin system. The synthesis of the carpets is done by Aerosol-Assisted Chemical Vapor Deposition on quartz substrates. The process allows to produce multiwalled nanotubes with a length up to 3.5mm and a volume fraction up to 20% . These carpets are in a second step densified with an aerospace qualified epoxy resin using liquid infusion process. After machining and polishing, thermal and electrical properties are measured at the reinforced film level on nano-composites with increasing carbon nanotube volume fractions. Through the thickness conductivity was investigated parallel to the nanotube orientation using the laser microflash method. As expected, results show an improvement of these properties, much higher than that is usually reported for dispersed nanotube reinforced composites. Thermal conductivity increases by a factor 100 when comparing the non-reinforced epoxy (0,19 W/m/K) to for the 12% volume fraction reinforced 50 nm diameter long nanotubes (22 W/m/K).