Thermoplastic sandwich radomes via thermal expansion molding for enhanced wet-state reliability

Moisture absorption significantly degrades the electromagnetic transparency of porous foam cores in high-performance radomes. To overcome this, we propose a synergistic strategy integrating molecular-level hydrophobic modification with a one-step thermal expansion molding process to fabricate adhesiveless, all-thermoplastic sandwich composites. Expandable microspheres were in-situ grafted with 1 wt% perfluorooctyltrichlorosilane (PFOCTS). This optimal concentration constructs a robust fluorinated barrier on the cell walls, increasing the water contact angle from 73.8° to 96.5° while circumventing the expansion-hindering "shell stiffening effect." Macroscopically, non-isothermal fusion bonding between the modified high-density polyethylene (HDPE) core and quartz fiber-reinforced skins eliminates the need for conventional adhesives. An optimized two- to three-layer skin configuration perfectly balances mechanical and electromagnetic performance, delivering excellent impact resistance, high interfacial peel strength, and >93% microwave transmission efficiency. Crucially, the composite demonstrates outstanding moisture resistance. Benefiting from a dual-defense mechanism—a dense macroscopic interface and a microscale fluorinated network—it retains >85% transmission efficiency even under water-saturated conditions, markedly outperforming its unmodified counterpart (64.8%). This work presents a highly recyclable structural solution with all-weather electromagnetic reliability for next-generation aviation radomes.