Ablation characteristics of carbon nanotubes reinforced novolacresin nanocomposites: Experimental and simulation approach

Abstract

Ablation rate and thermal conductivity for phenol- formaldehyde type novolac resin
reinforced with single walled carbon nanotubes (SWCNTs) have been studied via
experimental and simulation of Oxy – acetylene flame and Lee’s disc techniques respectively.
Simulation programs of heat transfer in three dimensions of ablative test for novolac and
novolac nanocomposites specimens were carried out using finite difference method (FDM).
Theoretical thermal conductivity was calculated according to microstructures model. Hotpress
technique was used to prepare the nanocomposites as well as novolac specimens using
flash molds at standard conditions. Thermal conductivity results show, that the values
increase progressively by succession of volume fraction of SWCNTs. Ablation rate behaves
inversely, where it drops at high volume fraction of SWCNTs. The thermal conductivity –
ablation rate relationship, displays two mechanisms, the first, associated with the starting of
ablation test, is recognized by ideal distribution of SWCNTs, which leads to good thermal
dispersion due to the formation of segregated network of thermal conducting paths. The
second mechanism is associated with in- run ablation test recognized by shearing cracks
appearance, which leads to earlier char production mechanism. Simulation thermal
conductivity results, , and when it compared with the experimental results, it observed, that
the experimental results, were located between the parallel and random direction simulation
values of SWCNTs, which is evidenced that the additives arrangement closed to parallel
direction more than random or perpendicular direction with respect to heat flux direction.
Keywords: Ablation, simulation, nanocomposites, and carbon nanotubes.