High-Velocity Impact-Induced Electromagnetic Degradation of Multifunctional Composite Laminates

Multifunctional radar-absorbing composites that simultaneously provide structural load-bearing capability and electromagnetic (EM) stealth performance are increasingly demanded in advanced engineering applications. However, their EM absorption behavior is highly sensitive to impact-induced structural damage, while the underlying degradation mechanisms remain unclear. In this work, the postimpact EM degradation mechanisms of a multifunctional composite laminate subjected to bird strike were investigated through experiments, progressive damage simulations, full-wave EM analysis, and transmission-line modeling. Experimental results show a progressive reduction in peak absorption depth while the resonance frequency remains nearly unchanged with increasing impact severity. The results further reveal that geometric deformation and interlaminar delamination affect the EM response through different physical mechanisms. Geometric deformation tends to shift the absorption peak toward lower frequencies, whereas interlaminar delamination progressively degrades the absorption capability and induces an opposite frequency-shift tendency near the impact surface. The competing effects of these two damage modes explain the experimentally observed frequency stability and identify interlaminar delamination as the dominant source of postimpact EM degradation. This work establishes a physics-based understanding of impact-induced EM degradation in radar-absorbing composite structures.