Electromagnetic response changes of unidirectional carbon fiber-reinforced polymer circuit-analog absorbers due to post-processing impact damage

This paper explores the effect that impact damage has on the microwave reflection coefficient of unidirectional carbon-fiber reinforced polymer (CFRP) circuit analog absorbers (CAA). Such damage can negatively impact the electromagnetic properties of radar absorbing materials (RAM) and degrade their performance. Three unidirectional CFRP samples comprised of a unidirectional CFRP lamina and foam spacer are fabricated using a wet-layup technique. The samples under test (SUTs) are then individually subject to controlled impact tests. A custom damage apparatus drops and guides a variable weight impactor from a known height towards the center of the SUT. After each damage phase, the complex relative permittivity, surface impedance, and the reflectivity when the samples are placed in an absorber configuration are measured from 4-18 GHz using a free- space measurement system. The change in these properties due to the impact are investigated as a function of frequency, angle, and damage.