Development of coaxial NiTi/viscoelastic polymer filament for enhanced damping and tunable energy absorption capabilities

The integration of high load-bearing capacity, minimal deformation, and high damping remains a major challenge for energy-absorbing materials. Here, we developed a custom coaxial polymer–metal filament fabrication system. By employing NiTi continuous filaments with high damping and tunable stiffness as the core and encapsulating them with a highly damping viscoelastic polymer shell, we fabricated coaxial NiTi/viscoelastic polymer filaments that simultaneously deliver superior damping capacity and robust load-bearing performance. The effects of filament diameter and polymer diluent concentration on the thermomechanical behavior and damping properties were systematically investigated. Hysteresis tests under varying loading rates were conducted to evaluate the rate-dependent energy dissipation behavior. Ball drop impact tests and simulations on the composite filament mesh demonstrated superior energy absorption capacity compared to pure NiTi mesh and other damping materials. Vibration isolation tests and simulations confirmed its excellent and tunable low-frequency isolation performance. This approach offers a new pathway to achieving an optimal balance between damping capacity and stiffness in NiTi-based energy absorbing materials, with potential applicability to other material systems and scalable manufacturing.