Improvement in Inter‐Layer Failure and Residual Flexural Properties of Carbon/Aramid Fiber Hybrid Composites With Multiscale Fiber‐Interleaving Under Low‐Velocity Impact Load

ABSTRACT Hybrid fiber‐reinforced polymer (HFRP) matrix composites are widely employed in aerospace and other fields owing to their excellent mechanical properties. However, their performance is often limited by interlaminar failures such as fiber fracture, matrix cracking, and delamination. This study proposes an interlaminar toughening strategy based on a synergistic combination of aramid pulp (AP) and carbon nanotubes (CNTs). Four AP/CNT systems with different areal densities were designed to construct a multi‐scale flexible bridging network, enabling a systematic investigation into their toughening mechanisms on the low‐velocity impact response and residual flexural strength of unidirectional carbon/aramid HFRP. Impact tests indicated that the resistance to impact increased with toughener concentration. The optimal impact performance was achieved at an AP areal density of 3.0 g/m 2 and a CNT density of 4.5 g/m 2 , with a peak load of 10.1 kN—an 11.2% improvement over the untoughened baseline. Conversely, post‐impact three‐point bending tests revealed that the optimal residual flexural strength of 232 MPa was reached with an AP/CNT areal density of 2.0/3.0 g/m 2 , representing a 69% enhancement. Microstructural analysis identified interfacial delamination and fiber fracture as the primary failure modes and confirmed that the AP/CNT system creates effective fiber‐bridging structures between heterogeneous layers. This suppresses interlaminar failure and significantly improves the overall structural stability. In summary, the synergistic AP/CNT toughening system effectively enhances both the impact resistance and post‐impact flexural performance of HFRP composites.