The influence of impact-induced damage on electromagnetic shielding behaviour of carbon fibre reinforced polymer composites

Increasing interest in multifunctional carbon fibre reinforced polymer (CFRP) composite structures for electromagnetic (EM) shielding prompts discussions on their EM shielding durability. Herein, the EM shielding effectiveness (SE) of impact damaged and artificial delamination conditioned CFRP laminates was characterised and compared to intact specimens. The SE in two frequency regimes was investigated: the UHF (0.03-1.5 GHz) and K-a band (26-42 GHz). The lower frequency SE experiments demonstrated a positive effect of impact delamination, ascribed to the enhanced absorption caused by multiple reflections. Concurrently, owing to the reduced skin depth, severe damage involving fibre fracture was required to induce noticeable SE changes at higher frequencies. The effect of artificial delamination was a strong function of the lay-up, with a significant deterioration in thin cross-ply laminates due to the impaired contribution of through-the-thickness conduction loss. The lower frequency results were simulated in CST Microwave Studio, demonstrating good agreement with experimental values.