内绝热层中芳纶中空烧蚀形貌的形成机理研究

The morphology evolution and the ablation mechanism of organic fibers in the flexible internal insulation materials upon high temperature ablation were investigated by using oxyacetylene flame, high-temperature iron plate (~1000℃) and thermogravimetry measurement. The morphological evolution characteristics of aramid fibers or acrylic fibers inside the carbonized layer under different ablation conditions were preliminary studied. The results show that after ablating under oxygen acetylene flame, the carbonized aramid fibers inside the char layer present a hollow ablative structure, whereas no fibrous structure could be detected for the PAN fiber reinforced composites. On the contrary, the carbonized PAN fibers is hollow, the carbonized aramid fibers are still solid in the char layer if ablated by high-temperature (1000℃) iron plate. Both kinds of fibers still maintain solid structure if heated with a slow heating rate. Therefore, the unique skin-core structure of aramid fibers is the intrinsic cause to form the hollow ablation morphology. Meanwhile, the external factors for the hollow structure would be ascribed to the cooling effect of pyrolysis gas on the skin-layer of aramid fibers and the rapid heating mode of sudden temperature rise.