Besides high-performance fibers, ceramics, metals, and smart materials, carbon fiber, ultra-high molecular weight polyethylene nonwoven fabric (UD fabric), and some composite matrix materials are also commonly used in bulletproof vest structures. They often serve as auxiliary or support layers, improving overall protective performance and weight reduction.
1. Carbon Fiber – A High-Strength, Lightweight Cushioning Layer Material
While carbon fiber itself has limited ballistic protection capabilities, its high modulus and low density make it an ideal backing or cushioning layer material.
It is commonly used in composite armor, positioned behind ceramic inserts to absorb residual impact energy, prevent backplate breakage, and reduce the risk of blunt force trauma.
It also has wide applications in the ballistic structures of helicopters, tanks, and ships; for example, aramid/carbon fiber hybrid composite plates can reduce weight by more than 30% compared to traditional steel plates.
2. Unidirectional Fabric (UD Fabric) – An Advanced Form of High-Performance Fibers
This is not a new material, but a composite fabric made by unidirectionally arranging ultra-high molecular weight polyethylene or aramid fibers and fixing them with resin.
Compared to traditional woven fabrics, UD fabric exhibits more uniform fiber stress, higher energy transfer efficiency, and significantly improved tensile strength.
At the same protection level, UD fabric can reduce weight by 20%-30% compared to traditional aramid fabrics, making it one of the lightest and strongest soft bulletproof materials currently available.
3. Resin and Polymer Matrix – The Invisible "Structural Glue"
In UD fabric, composite inserts, and other structures, thermosetting resins (such as epoxy resin) play a crucial role in bonding fibers and transferring stress.
The properties of the resin directly affect the overall rigidity and energy dissipation capacity of the material. While not directly providing "bulletproof" protection, it is a significant factor determining the effectiveness of bulletproofing.
4. Natural Fibers (Historical Applications) – Early Prototypes of Bulletproof Vests
In the late 19th century, multi-layered silk was used to make bulletproof vests, capable of withstanding low-velocity pistol bullets, but these were expensive and offered weak protection, and have since been phased out.
Modern research occasionally explores spider silk composite materials. For example, the University of Trento in Italy infused graphene into spider silk, achieving a strength 3.5 times that of natural spider silk, demonstrating potential applications, but mass production has not yet begun.
5. Novel Composite Additives – Key to Enhancing Ceramic Performance
During the sintering process of bulletproof ceramics, multiphase additive powders (such as Y₂O₃, AlN, etc.) are added to optimize the grain structure, improve density, and increase impact resistance.
While these trace additives do not independently constitute the bulletproof layer, they are crucial for enhancing the protective performance of high-end ceramics such as silicon carbide and boron carbide.
