Design and Preparation of a UV ‐Curable Epoxy Resin System for the Emergency Repair of Wave‐Transparent Composite Structures

ABSTRACT The radome is a critical wave‐transparent structure employed on aircraft. Damage to its skin directly degrades radar detection capability and compromises flight safety; therefore, a field‐deployable rapid repair strategy is urgently required. In this work, a UV‐curable epoxy resin system was developed for the emergency repair of radome skin damage. Two resin matrices, cycloaliphatic epoxy resin (EEC) and bisphenol‐A epoxy resin (E51), were evaluated for curing behavior, mechanical properties, thermal resistance, and dielectric characteristics, and an optimal formulation was selected to fabricate quartz‐fiber‐reinforced composites. Repair efficacy was verified through scarf‐repair experiments on honeycomb sandwich panels. The results indicate that E51 is susceptible to photo‐oxidative yellowing owing to its bisphenol‐A backbone, resulting in a reduced curing degree. By contrast, EEC exhibits excellent light transmittance; its optimal formulation attains a curing degree of 98.33% after 600 s of UV irradiation, with a tensile strength and modulus of 63.33 MPa and 3.46 GPa, respectively, and a glass‐transition temperature ( T g ) of approximately 140°C. The dielectric constant and loss tangent remain below 3.05 and 0.05, respectively, over 4–15 GHz. The quartz‐fiber‐reinforced composite exhibits tensile and flexural strengths of 370.90 and 390.15 MPa after 10 min of UV curing, with a dielectric constant of approximately 2.8 and dielectric loss below 0.1. Following repair, the edgewise compressive strength and X‐band transmittance exceed 93% of those of the intact structure, demonstrating the strong potential of this approach for field emergency repair of aircraft wave‐transparent structures.