Microwave absorption performance of surface textured PET-POFA composite bricks: effect of slot geometry and incidence angle

Abstract

This study presents the development and evaluation of PET-POFA composite bricks with surface slot arrays to improve electromagnetic absorption across the 1 to 12 GHz range, with particular emphasis on the X-band. CST Studio simulations were conducted on two slot geometries with lengths of 7.5 mm and 15 mm, corresponding to quarter-wavelength and half-wavelength resonances at 10 GHz. The results indicate that the 7.5 mm design produces broader and deeper absorption, including a pronounced dip within the X-band, while the 15 mm configuration exhibits shallower absorption and reduced impedance matching at higher frequencies. Bricks were manufactured using a mix design that replaced 10% of the sand with PET and 30% of the cement with POFA. The bricks were then evaluated using the NRL free-space arch method to assess their performance at incidence angles of 0°, 30°, and 60° in vertical orientation. Experimental measurements confirm that the 7.5 mm textured brick achieves reflectivity below –20 dB over wide frequency spans, with peak absorption reaching –39.36 dB in the X-band. In contrast, the 15 mm variant shows inconsistent performance and positive reflectivity at lower frequencies due to impedance mismatch, while the untextured control sample demonstrates comparatively lower absorption across all bands. The combined simulation and experimental findings establish that precise quarter-wavelength slotting in PET-POFA composites enables effective impedance matching and stable angular performance, highlighting a sustainable and high-performance solution for electromagnetic shielding in building applications.