Influence of Impact on Electromagnetic Response of Three-Dimensional Angle-Interlock Metacomposites

A radar absorbing structure named three dimensional angle-interlock metacomposites (3DAM) was proposed based on the metamaterial units formed by three dimensional angle-interlock structure and ferromagnetic microwire as the functional element. To investigate the electromagnetic damage tolerance of 3DAM and its electromagnetic response towards impact, a 10J impact was applied on the 3DAM, and three representative regions, including impact center, impact edge and no impact have been selected. From the perspectives of permittivity, S parameters and impedance matching, the electromagnetic response of 3DAM at different regions have been investigated. It has been found that 3DAM presented negative permittivity before and after impact under X band, and the resonance frequency can be adjusted by impact position as a result of the structural change of metamaterial units formed by ferromagnetic microwires. The permittivity shifted to positive with less influence by impact under Ku band. It has been verified by micro-CT that the movement and fracture of ferromagnetic microwires induced by impact led to a dimensional change of metamaterial units; therefore, reconfiguration of metamaterial units dominated the electromagnetic response of 3DAM after impact, which is advantageous to maintain the absorption ability. The absorption mechanism for the 3DAM before and after impact has been explored by both simulations and equivalent RLC circuit analyses. It has been found that the reconfiguration of microwires caused by impact led to a circuit rearrangement, hence, the electromagnetic response and absorption keeps high efficiency after impact, exhibiting a high electromagnetic damage tolerance.