Effect of Thermoset Matrix Type on the Mechanical, Thermomechanical, and Electromagnetic Performance of Coremat Interlayered Carbon, Glass, and Aramid Fiber-Reinforced Hybrid Sandwich Composites

Fiber-reinforced polymer composites are attractive multifunctional material systems for aerospace, defense, and transportation because of their low density, high specific mechanical properties, and tailorable electromagnetic response. This study comparatively evaluated the effects of fiber system, thermoset matrix, and hybridization on the mechanical, thermomechanical, and electromagnetic behavior of Coremat interlayered sandwich composites containing carbon, glass, and aramid fabrics with polyester, vinylester, and epoxy matrices. Eighteen configurations were fabricated by hand lay-up and evaluated by tensile, three-point bending, heat deflection temperature (HDT), Vicat softening temperature (VST), and two-port S-parameter measurements over 4–40 GHz. The carbon/epoxy configuration exhibited the highest tensile strength (231.2 MPa), whereas the glass/vinylester configuration showed the highest flexural strength (160.5 MPa), HDT (128.0 °C), and VST (132.7 °C). The relatively low standard deviations across the tested configurations indicated consistent experimental repeatability and limited within-configuration dispersion. Carbon-containing systems strongly suppressed electromagnetic transmission; however, the single carbon systems were predominantly reflection driven. The carbon/glass polyester hybrid S10 provided the highest total shielding effectiveness (38.45 dB) at an overall laminate thickness of 3.30 mm, corresponding to a normalized shielding effectiveness of 11.65 dB/mm, while the carbon/aramid epoxy hybrid exhibited the highest incident-power absorption ratio (22.4%) together with very low transmission (0.22%). Overall, the results show that fiber system, matrix type, and hybrid architecture should be selected jointly when balancing structural, thermomechanical, and electromagnetic requirements.