Radar Transparent, Impact-Resistant, and High-Temperature Capable Radome Composites Using Polyetherimide-Toughened Cyanate Ester Resins for High-Speed Aircrafts through Resin Film Infusion

High-temperature capable (T g: 280–290 °C), broadband radar transparent [ε′: 3.3–3.9; ε″: 0.02–0.17; tan δ: 0.01–0.04 and transmission loss: −0.18 to −1.26 dBl in C, X, and Ku bands (5.4–18 GHz)], composites were developed using polyetherimide (PEI)-toughened bisphenol E cyanate ester resin and E glass fabrics through an out-of-autoclave process called resin film infusion at a range of PEI weight fractions via a solvent-free method. Their pronounced increase in impact resistance in terms of mode I interlaminar fracture toughness (G Ic; 50–100%), postimpact residual compressive strength (>85%), and enhanced structural properties such as tensile strength, compressive strength, in-plane shear strength, and interlaminar shear strength compared with control laminates, which later re-corroborated with a structure–property relationship using surface morphology proving that PEI-modified cyanate esters can find extensive applications in impact-resistant composite radomes for high-speed aircrafts.