Thermal ablation‐insulation performance, microstructural, and mechanical properties of carbon aerogel based lightweight heat shielding composites

• Published in: Polymer engineering and science 2021-05, Vol.61 (5), p.1338-1352
• Main Authors: Seraji, Mohammad Mehdi, Arefazar, Ahmad
• Format: Article
• Language: English
• Subjects: Ablation; ablation‐insulation performance; Aerogels; carbon aerogel; Carbon compounds; Composite materials; Composition; Compressive strength; Heat shielding; Heating rate; Insulation; Insulators; Lightweight; Mechanical properties; Methods; Microstructure; Morphology; Oxyacetylene; phenolic resin; porous ablator; Protection systems; Shielding (Heat); Structure; Thermal conductivity; Thermal properties; Thermal protection
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.25648

In this study, carbon aerogel based lightweight composite ablators (CALCAs) with different densities and microstructures were prepared using the vacuum impregnation method. The mechanical strength and morphology of CALCAs were investigated. Ablation‐insulation performance of the samples was also evaluated by an oxyacetylene flame test with a constant heating rate of 2.5 MW/m2. Moreover, the structural evolution during the ablation was studied and the ablation mechanism of CALCAs was proposed. The porous insulators showed good compressive strength (3.2–9 MPa) and low thermal conductivity (lower than 0.35 W/mK). Besides the tunable density, the low recession rate (as low as 0.117 mm/s), and good ablation‐insulation performance (175°C at 25 mm and 125 at 35 mm in‐depth), these lightweight porous heat shielding composites are promising candidates to use as the thermal protection systems for aerospace applications. A novel application was introduced for carbon aerogels. These porous structures were used as carbon preforms for lightweight high‐temperature sacrificial insulators. Porous carbon‐phenolic ablators were prepared based on novolac resin. The resin infused‐3D carbon aerogels showed high recession resistance and desired insulation performance with low densities. The effect of resin loading on the mechanical strength of ablators was more effective than the density of carbon preforms. The ablation mechanism changed from surface ablation to volume ablation with decreasing of ablators' density .