Electromagnetic damage tolerance for radar absorbing composite structures with impact damage

Abstract Radar absorbing structures (RAS) based on fiber reinforced plastics, which is applied to the external structures of low-observable aircrafts, is vulnerable when exposed to a variety of external impacts during aircraft operations. The general composite structure is designed with the concept of damage tolerance to ensure durability and structural integrity. Composite RAS requires both structural and electromagnetic characteristics. Therefore, it is necessary to establish the concept of structural and electromagnetic damage tolerance considering the degradation of electromagnetic performance due to impact damage. In this study, a concept of electromagnetic damage tolerance of a RAS is proposed. Impact damage to RAS specimens and structural damage is detected using non-destructive inspection. Moreover, rate of variation in electromagnetic (EM) wave absorption performance with impact energy is quantified through the measurement of return loss of EM wave before and after impact using free-space measurement. This is obtained by investigating the relationship between electromagnetic properties and structural damage tolerance for the laminated type of RAS.