Advances in the thermal properties of Nomex honeycomb composites

Abstract Nomex honeycomb composites are being used more frequently in aerospace, transportation, and defense applications due to their exceptional thermal performance, mechanical strength, and low density. This review comprehensively evaluates the most recent developments in the thermal properties of Nomex honeycomb composites, with a particular focus on their fire performance, thermal stability, and effective thermal conductivity. The effective thermal conductivity (k_eff) of Nomex honeycomb cores typically ranges from 0.03 to 0.06 W/mK, as revealed by a thorough examination of the published literature. This value is primarily determined by the density of the core, the thickness of the wall, the distribution of resin, and the geometry of the cells. The range of near-insulation values to above 13 W/mK has been demonstrated to be extended by structural and material modifications, such as the integration of highly oriented graphite films and phenolic foam infill. This has enabled multifunctional thermal management. Thermogravimetric analysis consistently identifies a two-stage decomposition profile, with phenolic resin degradation occurring between 350 and 450 °C and aramid fiber breakdown between 450 and 600 °C. This results in char residues of 25–35%, which act as protective fire barriers. Cone calorimeter evaluations corroborate adherence to rigorous fire safety standards, including FAR 25.853, by confirming extended ignition times and low heat release rates. The bonding quality, void content, and ensuing thermal-mechanical performance are all significantly influenced by the manufacturing route, which includes hand lay-up, autoclave curing, resin transfer molding, and hot compression molding. This review also underscores a substantial lacuna in the systematic correlation between long-term thermal-mechanical reliability and manufacturing-induced defects under realistic service conditions, and it identifies hybrid core architectures as a design domain that has been largely unexplored. The results offer a comprehensive reference for engineers who are responsible for the development of next-generation sandwich structures that are thermally adaptive and lightweight, with applications in hypersonic, electric mobility, and defense platforms.