Investigation of the Mechanical Performance and Damage Mechanisms of Hybrid Composite Tubes with Mixed Stacking Sequences

In this study, the effect of stacking sequence on the mechanical behavior and damage evolution of carbon- and glass-fiber-reinforced hybrid composite tubes manufactured by the filament winding method was experimentally investigated. The tubes were produced from E-glass and carbon fibers in a Huntsman epoxy matrix, with an inner diameter of 22.5 mm and an outer diameter of 28.5 mm, in two configurations that differ in both the fiber placed in each layer and its winding angle: an inner [±45]2 carbon layer/outer [±75]2 glass layer (C45) and an inner [±45]2 glass layer/outer [±75]2 carbon layer (G45). The fiber volume fractions ranged from 0.53 to 0.61 and the measured densities from 1.68 to 1.84 g/cm3. Five specimens per configuration (n = 5) were tested under radial compression and three-point bending, and their fracture mechanisms were characterized by scanning electron microscopy (SEM) and optical microscopy. Energy absorption was quantified through the specific energy absorption (SEA). Under radial compression, the C45 configuration exhibited a higher peak force (4209 ± 322 N versus 3573 ± 136 N) and a higher SEA (2.64 ± 0.13 J/g versus 2.06 ± 0.03 J/g). Under three-point bending, C45 again reached a higher flexural strength (92.8 ± 4.5 MPa versus 85.1 ± 3.0 MPa); however, despite failing at a markedly lower peak force, the G45 configuration absorbed a comparable total energy (66.96 ± 2.83 J versus 62.88 ± 6.26 J) and reached a comparable SEA (1.13 ± 0.06 J/g versus 1.08 ± 0.14 J/g), reflecting the ductility-driven damage tolerance imparted by the glass inner layer. Across all metrics, the G45 configuration displayed a consistently lower coefficient of variation (e.g., 3.82% versus 7.64% for radial peak force), indicating greater reproducibility and structural predictability. SEM observations revealed that the C45 specimens failed through sudden fiber fracture and delamination driven by the high stiffness mismatch, indicating brittle behavior, whereas the G45 specimens exhibited progressive damage through matrix crushing and fiber pull-out. The findings indicate that the C45 configuration is favorable where maximum load-bearing capacity and stiffness are targeted, whereas the G45 stacking sequence is advantageous where energy absorption, damage tolerance, and predictable progressive failure are critical.