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    Electromagnetic interference shielding, mechanical, and flame retardant behaviors of Ti3C2Tx-MXene/glass fabric epoxy hybrid composites
    (Elsevier Science Sa, 2024) Yilmaz, Ayten Nur Yuksel; Bedeloglu, Ayse Celik; Yunus, Doruk Erdem
    This study investigates the manufacturability and electromagnetic shielding effectiveness (EMI-SE) of Ti3C2Tx/ MXene-coated glass fabric laminated composites for aerospace applications. MXene-coated fabrics were produced using a dip-coating method. The effects of varying dipping counts (5 and 10) and different configurations of fabric arrangements on the EMI-SE of the composites in the X-band range (8.2-12.4 GHz) were investigated. Glass fabrics with 5 and 10 dips showed average surface resistances of 38.56 Omega/sq and 23.17 Omega/sq, respectively. In both the 5- and 10-dip composite sets, the total EMI-SE increased with the number of MXene-coated glass fabric layers in the composite. The 5MXC5 and 10MXC5 specimens, with conductive fabric in all layers, had average total shielding effectiveness (SET) of -18.75 dB and -23.21 dB, respectively. These values are 147.05 % and 205.80 % higher than the neat glass fiber-epoxy composite (C1). Flammability, bending, ILSS, and hardness tests were conducted on these composites. Increasing the MXene content reduced the burning rate, with 10MXC5 exhibiting a 26.31 % lower burning rate compared to C1. However, higher MXene content slightly decreased bending and ILSS values. Optical microscope examination of the fracture surfaces revealed that this decrease was due to delamination damage.
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    Enhancing mechanical and flame retardant characteristics of glass fiber-epoxy laminated composites through MXene and functionalized-MXene integration
    (Elsevier, 2024) Yilmaz, Ayten Nur Yuksel; Bedeloglu, Ayse Celik; Yunus, Doruk Erdem
    MXene, a 2D transition metal carbide and nitride with graphene-like layered structures, has become one of the preferred choice for nano-reinforcement in polymer matrix composites in recent years due to its outstanding properties such as specific surface area, excellent thermal and mechanical characteristics, and high conductivity. In this study, the glass fiber-epoxy laminated composites reinforced with Ti3C2Tx-MXene (M)/ functionalizedMXene (FM) were produced using the hand lay-up procedure followed by vacuum bagging process. The effects of varying filler amounts (0.125, 0.25, 0.375, and 0.5%) on the mechanical and flame retardancy properties of glass fiber-epoxy composites were examined. In both M and FM reinforced composites, the highest values of mechanical strengths were obtained with a 0.25% filler, while a decrease in mechanical strengths was observed beyond this reinforcement amount. The 0.25 wt% FM-reinforced composite exhibited 19.21%, 27.55%, and 12.40% higher tensile, flexural, and interlaminar shear strengths (ILSS) than the pristine glass fiber-epoxy composite (N-C). Post-test analysis revealed the presence of matrix cracks, fiber breakage, and fiber pull-out damages were observed on the surfaces of composite samples. The flame retardant properties of the composites were enhanced with the addition of MXene reinforcement, and 0.5FM-C exhibited 25.50% lower burning rate than N-C.
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    Tensile behavior of C/GFRP-steel hybrid rebars: Effect of volume fraction and helical angle with a proposed analytical model
    (Elsevier, 2026) Senaysoy, Safa; Yilmaz, Ayten Nur Yuksel; Bedeloglu, Ayse; Altin, Yasin; Sakcali, Gokhan Baris
    This study examines the tensile properties of hybrid rebars consisting of a steel core wrapped with layers of Carbon Fiber-Reinforced Polymer (CFRP) or Glass Fiber-Reinforced Polymer (GFRP). The mechanical performance of the Steel-FRP composite bars (SFCBs) was evaluated through axial tensile tests considering two primary parameters: (i) the longitudinal FRP volume fractions (33 %, 40 %, and 47 %) and (ii) the helical wrapping angles (0 degrees, 30 degrees, and 60 degrees). Although SFCBs have gained increasing attention as an alternative to fully FRP or conventional steel reinforcement, the combined influence of fiber volume fraction and helical orientation on their tensile response has not been clearly established. Experimental findings demonstrated the influence of fiber volume fraction and helical angle on the tensile properties of SFCBs. Specimens coated with carbon exhibited greater strength than those coated with glass, especially at larger wrapping angles, while the glass-coated SFCB specimens demonstrated a wider range of deformation capability. The specimen with a 47 % volumetric fraction and a 60 degrees helical wrap exhibited a 21.8 % increase in yield stress compared with that of the steel bar, whereas its glass-fiber counterpart exhibited a 15.9 % increase. Maximum strength was significantly higher in carbon-SFCB rebars than in glass-SFCB ones. In contrast, glass-SFCB rebars showed 59 % higher ultimate strain. As the volume fraction increased, the influence of the helical angle on ultimate strength decreased. Increasing the helical angle from 0 degrees to 60 degrees enhanced the ultimate strength by up to 32 % in carbon-SFCBs and approximately 12 % in glass-SFCBs at a 33 % volume fraction. An analytical model was proposed to predict a five-zone stress-strain behavior, taking into account the effects of volumetric fraction and helical angle. The proposed model effectively replicated the stress-strain patterns of hybrid rebars in every zone with a satisfactory level of accuracy. Generally, the calculated mean absolute percentage errors for key mechanical parameters such as initial stiffness, yield stress, and fiber-contributed stiffness were below 15 %. This study offers a practical framework for designing SFCBs with customised mechanical properties for sophisticated RC applications.