Shear thickening fluids and gels as reinforcement in ballistic vest: an update review

Shear thickening fluids (STFs) and shear thickening gels (STGs) are smart materials that undergo a reversible, rapid transition from a low-viscosity state to a highly viscous or quasi-solid phase when subjected to shear rates above a critical threshold. This dynamic thickening behavior enables efficient dissipation of impact energy, making these materials promising candidates for applications in ballistic protection, shock absorption and vibration mitigation. This review provides an updated and comprehensive analysis of STF- and STG-based reinforcement strategies for high-performance fabrics used in flexible armor systems. It examines how these materials enhance inter-yarn friction, restrict yarn pull-out, and improve load transfer, thereby increasing the mechanical robustness, durability and energy-absorption capacity of ballistic textiles. Recent advances from the past decade, particularly from 2021 to 2024, are synthesized to compare formulation approaches, rheological behavior, microstructural mechanisms, and ballistic performance. Critical challenges related to environmental stability, long-term durability, large-scale processing, and compliance with ballistic standards are also discussed. By integrating current knowledge and identifying unresolved research gaps, this review highlights the growing potential of STFs and STGs to advance next-generation personal protective equipment and to significantly improve the performance and reliability of flexible ballistic body armor.