Structural performance of mortar elements strengthened with intraply hybrid composite fabrics: Combined effects of fiber hybridization and reinforcement orientation

The performance of externally bonded fiber-reinforced polymer (FRP) systems depends not only on the constituent fibers but also on fiber hybridization, reinforcement architecture and loading condition. This study investigates three intraply hybrid fabrics, namely carbon–glass (CG), aramid–carbon (AC) and glass–aramid (GA), applied to mortar elements in horizontal (0°), vertical (90°) and diagonal (45°) orientations. Epoxy-impregnated fabrics were characterized by direct tensile tests, and strengthened mortar prisms and cubes were tested in three-point bending and axial compression. The effects of hybrid composition and orientation were separated by two-way ANOVA with Tukey and Dunnett post-hoc tests. Both factors, and above all their interaction, significantly affected tensile, flexural and compressive strength (interaction p < 0.001; partial η² = 0.756, 0.684 and 0.928). AC-H reached the highest tensile strength (178.18 MPa), whereas CG-D achieved the highest flexural strength (39.41 MPa), 5.9 times that of the reference (6.66 MPa); all strengthened prisms improved the flexural strength by 141–492%. Under compression, CG-V (53.70 MPa) and GA-H (53.51 MPa) were statistically equivalent and about 16% stronger than the reference, whereas vertical AC and GA layouts significantly reduced the strength (by up to 40% for GA-V). For every hybrid, the horizontal/vertical ranking was identical in tension, flexure and compression, because the horizontally oriented fiber family acts as longitudinal crack-bridging reinforcement in the prisms and as hoop confinement in the cubes. Placing the stronger fabric direction horizontally was therefore beneficial under both loading modes, while the diagonal layout was advantageous only in flexure. The configuration with the highest tensile strength did not provide the best structural performance. CG-D is recommended for flexure-dominated demand and CG-V or GA-H for compression, CG-V offering the most balanced response. These laboratory-scale results provide a basis for structural-scale investigations of hybrid strengthening of mortar and masonry elements.