Environmental Effects: Ablation of C/C Materials—Surface Dynamics and Effective Reactivity

Microstructure and gas-surface interaction studies of a 3D carbon/carbon composite in atmospheric entry plasma

“…Under argon flow the intra-bundle matrix surface lies above the fibers instead of below (see Figure 7). This "reverted" behaviour agrees with previous studies [27,9]. The differences between flat and hemispherical samples will be dis-…”

“…Nonetheless, despite this appreciable uncertainty, we have identified (see Table 5) that horizontal bundles are more resistant than the vertical bundles, themselves slightly more resistant than the matrix octets (as far as average values can be determined for these more disorganized components). For sublimated sample, as evidenced in previous tests [9], the reactivity is reversed between fibers and intra-bundle matrix.…”

“…From them, it is concluded that the surface of the horizontal bundles are lying some 8 µm above the vertical ones, themselves lying less than 10 µm above the octets, this last value being only approximate because of pores in the octets. These results are surprising because the vertical fiber bundles have been described as the most resistive phase [9]. Actually, measurements in vertical bundles are poorly accurate too, because only fiber tips can be seen by the microscope.…”

“…Additionally, a thin interface (approximatively 20 µm) separates these components. The relative height of these components after ablation is governed on the one hand by the competition between surface reaction and gas species transfer, which depends on the fluid and on the material, and on the other hand on the reactivity ratios, which are only material characteristics and are defined as [28,10,9] :…”

“…These phenomena are collected in the generic term of ablation. They are usually globally endothermic, transforming the thermal energy into mass loss and surface recession, whilst the remaining solid material insulates the vehicle substructure [9].…”