Since the interlayer film in laminated glass seems soft, how on earth can it stop a high-speed bullet?

Since the interlayer film in laminated glass seems soft, how on earth can it stop a high-speed bullet?

Layer Structure of Bulletproof Glass
Bulletproof glass is essentially a special type of laminated glass. There is no fixed number of layers (commonly ranging from three to multiple layers), but functionally it can be divided into three core layers:

1. Load-bearing layer (strike face): Usually made of thick, high-strength glass (such as chemically tempered glass or high-alumina glass). Its role is to withstand the impact first, consume the bullet's kinetic energy through fracturing, and attempt to deform or blunt the bullet, reducing its penetrating power.
2. Transition layer (intermediate layer): Generally uses organic adhesive materials (such as PVB, PU, SGP film, or polycarbonate sheets). This layer has strong adhesion and is responsible for absorbing most of the bullet's remaining impact energy, altering the bullet's direction of travel, and preventing it from penetrating further.
3. Safety protection layer (back face): Mostly uses high-strength glass or high-toughness transparent organic materials (such as polycarbonate PC sheets). It uses its own elasticity and toughness to absorb the final impact energy, ensuring the bullet cannot penetrate, while also bonding flying fragments to prevent secondary injury.

Why Laminated Glass Can Stop Bullets
The reason laminated glass can stop bullets lies in the physical properties of the interlayer film (such as PVB film) and the synergistic effect of the multi-layer structure:

• Bonding and containment: The interlayer film has extremely strong adhesion. When the glass shatters upon impact, the fragments are firmly bonded to the film and will not fly around, maintaining the integrity of the entire glass panel and preventing penetration and fragment injuries.
• Kinetic energy absorption: High-quality film (such as SGP or thick PVB) has high tear strength and toughness. When a bullet hits, the film layer absorbs the bullet's kinetic energy through its own stretching and deformation, acting as a buffer and preventing the bullet from advancing further.
• Multi-layer retardation: Bulletproofing is not achieved by a single film alone. When the bullet penetrates the outer hard glass, its energy is already consumed and it becomes deformed; upon entering the film layer, it is adhered to and retarded; finally, it is stopped by the inner high-toughness material. This "hard-soft-tough" combination achieves the bulletproof effect.