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Introducing porosity into structures is recognized as a practical strategy to achieve lightweightness and insulation for ablatives, but reduced matrix density leads to the weakening of mechanical and anti-ablation performances. Herein, a trade-off design of the porous structure is developed for integrating high-strength, insulation, and anti-ablation abilities into mid-density nanoporous phenolic composites (NPC). Benefiting from a narrow nanopore size (20–62 nm) of the matrix, thermal conductivity of NPC can be effectively limited within 0.079–0.115 W/(m·K), while showing a mid-density of 0.89–1.04 g/cm3. Meanwhile, NPC shows a considerable axial tensile strength of 130.2–177.8 MPa and out-of-plane compressive strength of ∼300 MPa due to the compromising porosity (34–62%) and reinforcing of the 3D needle-punched quartz fiber preform. Besides, NPC exhibits excellent oxidation resistance in static radiation heating (1000 °C) and outstanding insulation and ablation resistance under an oxy-acetylene heat flux of 1.76 and 4.18 MW/m2 with the linear ablation rates of ∼0.102 and ∼0.185 mm/s, respectively. The results will further promote the development and application of phenolic ablatives in extreme re-entry environments.

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