Abstract: Structural integrity and performance reliability of microwave-absorbing coatings are critical to the operational survivability of radar-absorbing structures throughout their service life. To address performance degradation induced by in-service coating damage, this study systematically investigated characteristic damage modes and developed representative microwave-absorbing coating specimens exhibiting prototypical damage morphologies. Using a carbonyl iron powder/organic silicone resin composite absorber as the model system, a 1.0-mm-thick functional coating was uniformly deposited onto a titanium alloy substrate via spray coating. Subsequently, by controlling the geometric parameters (position, area, depth) of three typical damage forms (scratch, wear, and detachment), a series of damaged samples were designed and fabricated, yielding standardized specimens for controlled experimental evaluation. Reflectivity was measured across the 2-18 GHz frequency band using the arch (bow-tie) method. Systematic analysis revealed the distinct influence of damage type, extent, and severity on electromagnetic wave absorption performance. Results indicate that for damage areas ≤20%, superficial scratches and mild wear (depth ≤0.4 mm) cause only marginal degradation, and the coating retains effective absorption (reflectivity ≤-10 dB) within the 8-18 GHz band. In contrast, detachment exhibits the most pronounced detrimental effect. Once the delaminated area reaches 10%, the reflection loss exceeds -10 dB across the target band. The critical damage parameters (wear in the central area (form 3#), depth 0.6 mm, area 20%; edge and strip like detachment (forms 2# and 3#), area 20%-30%) determined in this study provide key experimental basis for the subsequent damage assessment and repair research of microwave absorbing coatings.

Key words: carbonyl iron powder, absorbing coating, damaged sample, microwave absorption performance, reflectivity