Bulletproof vests are primarily made of high-performance fibers, ceramics, metals, and smart materials. These materials are combined in various ways to effectively absorb and disperse the kinetic energy of bullets.
Based on structure and application, the materials used in bulletproof vests can be categorized as follows:
High-performance fiber materials: These are the core of soft bulletproof vests. Common examples include:
Kevlar: Developed by DuPont, it is more than 5 times stronger than steel, yet only 1/5 the density. It possesses excellent tensile strength and is widely used in bulletproof vests and helmets.
Ultra-high molecular weight polyethylene (UHMWPE): Such as Dyneema® and the domestically produced "Lilun," it has a specific strength up to 15 times that of steel and is 20%-30% lighter than aramid for the same level of protection. It has become the mainstream soft bulletproof material globally. However, its high-temperature resistance is poor; its performance degrades above 70°C.
Unwoven fabric (UD fabric): Made by unidirectionally aligning fibers and curing with resin, it boasts high energy diffusion efficiency and is one of the strongest and lightest bulletproof fabrics currently available.
Rigid materials: Used to enhance protection levels and withstand rifle bullets:
Ceramic materials: Such as alumina, silicon carbide, and boron carbide, these have extremely high hardness. Upon bullet impact, they shatter and dissipate most of the bullet's kinetic energy, often used as the receiving surface of bulletproof inserts.
Metallic materials: Including special steels, aluminum alloys, and titanium alloys, these absorb energy through deformation and fracture, but are heavy and mostly used in early bulletproof vests or helicopter occupant protection.
Composite and smart materials:
Non-Newtonian fluids (shear-thickening fluids, STF): Normally soft, they harden instantly upon high-speed impact, significantly enhancing the impact resistance of fiber layers. They are often used in combination with Kevlar to form a new generation of "liquid bulletproof vests."
Carbon fiber: Used in cushioning layers, it combines high strength and lightweight design, further absorbing residual energy and reducing the risk of blunt force trauma.
Modern mainstream bulletproof vests mostly adopt a "soft-hard composite" design. For example, the outer layer is a soft layer of Kevlar or UHMWPE to absorb initial kinetic energy, the middle layer is a ceramic insert to break up the bullet, and the inner layer is cushioned with carbon fiber or STF material, achieving a balance between lightweight and high protection.
