Lightweight 3D Five‐Directional Hybrid Braided Spacer Composites With UHMWPE /Carbon Fiber Yarns for Enhanced Impact Resistance and Structural Stabi

ABSTRACT

Three‐dimensional braided composites (3DBCs) offer superior delamination resistance, structural designability, and impact resistance over traditional laminates, yet achieving simultaneous lightweight, structural stability, high strength, and energy absorption remains challenging. Herein, ultra‐high molecular weight polyethylene (UHMWPE) with the lowest density among high‐performance fibers was employed as braided yarns to construct three‐dimensional continuous networks. Five axial yarn systems—UHMWPE, three UHMWPE/carbon fiber (CF) hybrid combinations, and CF—were designed to fabricate lightweight three‐dimensional five‐directional braided spacer (3D5dBS) composites. Three‐point bending, quasi‐static compression, and low‐velocity impact tests (10, 15, 20 J) were conducted. Results show that CF‐axial specimens (Z4, UHMWPE:CF = 0:1) achieved the highest bending strength (271 MPa), bending modulus (14.9 GPa), and compression modulus (770 MPa), along with superior energy absorption under identical deflection. Under 10, 15, and 20 J impacts, these specimens exhibited the highest peak loads (4.9, 5.8, 7.1 kN), elastic stored energy and post‐impact residual strength, alongside the lowest energy dissipation ratio and damping coefficient, indicating minimal damage. This performance is primarily attributed to the significantly increased equivalent stiffness from CF axial yarns, which effectively reduced face sheet and spacer‐supporting region deformation during impact, while the synergistic effect between UHMWPE braided yarns and CF axial yarns maintained structural stability and integrity.