High‐Rate Axial Crushing and Damage Evolution of 3D Five‐Directional Glass/Carbon Hybrid Braided Composite Tubes: Effects of Yarn‐Level Fiber Placement

ABSTRACT Three‐dimensional five‐directional (3D5d) braided composite tubes are promising thin‐walled energy absorbers; however, how glass/carbon fiber placement in the braided and axial yarn systems governs high‐rate crushing and damage evolution remains insufficiently understood. In this study, four 3D5d architectures were designed and compared: CF‐CF, GF‐GF, CF‐GF, and GF‐CF, where CF and GF denote carbon and glass fibers, respectively, and the A‐B notation specifies the fiber types in the braided and fifth‐direction axial yarn systems, respectively. Split Hopkinson pressure bar (SHPB)‐based high‐rate axial compression tests were performed under driving gas pressures of 0.1–0.5 MPa and integrated with digital image correlation (DIC), stereomicroscopy, scanning electron microscopy (SEM), and X‐ray micro‐computed tomography (micro‐CT) to relate the nominal structural response to multiscale damage evolution. At a driving gas pressure of 0.5 MPa, the GF‐CF architecture reduced the carbon‐fiber volume fraction by 66% relative to CF‐CF, while achieving a mean peak nominal stress of 373 MPa and an early‐stage specific energy absorption (SEA) of 5.4 J/g over 0%–4% nominal strain, equivalent to 103% and 98% of the corresponding CF‐CF values, respectively. DIC and post‐impact damage analyses showed that GF‐CF promoted more distributed strain localization and a shallower, less connected inward crack topology, thereby limiting crack penetration into the tube wall. These results demonstrate that combining carbon axial yarns with glass braided yarns offers a carbon‐efficient design strategy for 3D5d braided composite tubes subjected to high‐rate axial crushing.