Metal Foams | R&D of Ballistic Protection Systems for Modern Warfare Applications
What is ballistic Material? Where is it used?
The most common hard armor will use Ceramic plates as baffles, but ceramic shatters on impact and loses its energy for sustained combat. Most metal plate armor has the same problem of bullets flaking off on impact. These fragments can cause injury to the wearer of the armor. Wearers applying secondary armor patches to their faces can be very uncomfortable and add cost to the individual, company, or government. The development of lightweight combat technologies such as aircraft and amphibious vehicles, as well as the need to increase the mobility of ground forces, are requiring ballistic materials that continue to reduce the weight of armor while improving ballistic performance.
Ballistic shields are available in a variety of types and grades. These materials are used to protect glass, vehicle armor, body armor and shields. Laminated plastic sheets offer a wide range of protection, from certified sealed glass to tertiary ballistic materials. Ballistic materials are usually rigid, but can also be soft. They can be complex, such as Kevlar, UHMWPE, Lexan or carbon fiber composites, or simple, such as aluminum, steel, titanium or other alloys.
With the advancement of technology, ballistic body armor has changed radically. The bulletproof undershirt market is witnessing a revolution that is safer and lighter. This has opened up a new battleground for Composite Metal Foam (CMF) technology, taking it out of the realm of medical procedures ranging from car bumpers to knee replacements.
Single or composite foam metals are responsible for this - these are structural foams in the form of hollow metal spheres, which are embedded in ballistic devices as a core material, but also as intermediates in complex applications such as armor steel, ceramics, and fiberboard. The foam not only stops the high velocity impact of bullets and shells, but also completely crushes them. Even armor-piercing bullets, designed specifically to tear through armor, cannot penetrate them.
For the warrior, foam metal in personal protective equipment uses include:
- General Purpose Bulletproof Vests
- Active Flotation Bulletproof Vests
- Passive Floating Bulletproof Vests
- Tactical ballistic helmets
- Ballistic shoulder and side protection armor sets
- With visor and spine protection
- Ballistic shields
For heavy armored instruments as well as survival gear, foam metal is used for a variety of applications including:
- Making composite armor
- Making mine-resistant base plates for vehicles
- Making military drop boxes
What is Foam Metal? What is Foam Metal and what are its incredible properties?
Foam metal is a porous metallic material that forms a three-dimensional mesh structure in a metallic matrix. Since there are many pores in the metal foam, the size, number, uniformity, connectivity and sealing of the pores affect its properties. Parameters that are closely related to the properties of foam metals include pore size, total porosity, effective porosity, density and specific surface area.
Foam metal, as a new type of material with both metallic properties and some special physical properties of non-metallic materials, is receiving more and more attention. The main properties of foam metal are as follows:
- Ultra-light material (75-95% of the volume consists of void space)
- Very high porosity
- High compressive strength combined with good energy absorption properties
- Low thermal conductivity
- High strength
Impact energy absorption principle of foam metals
In addition to being used commercially for filtration, noise reduction, insulation and catalyst carriers, metal foams are a strong candidate for application in composite armor systems in the field of energy absorption.
As a ballistic protection device, foam metal is a lightweight, high-strength foamed material manufactured using hollow metal spheres embedded in a solid metal matrix. This material has shown excellent mechanical properties compared to any other metallic material. These superior qualities of the foam metal trap the energy rapidly at high ballistic velocity impacts compared to quasi-static loading.
Commercially available energy absorbers, which typically absorb kinetic mechanical energy by compressing or deflecting it at a relatively constant stress over a long distance, function somewhat similarly to springs, but they bounce back, making them energy storage devices rather than energy absorbers.
The porous structure of metallic foams gives them a unique stress-strain curve; once the applied stress exceeds the extrusion plateau, the foam will begin to compress at a fairly constant stress to about 50-70% strain. The extension of the stress/strain curve defines the behavior of an ideal energy absorber.
How does foam metal work on body armor?
Foam metal has been proven to trap bullet fragments and protect you from any secondary damage. Most military body armor uses a Kevlar-like material as a back layer, which is usually rated III-A and will stop handgun rounds on its own. Soft armor stops bullets by dissipating energy, and since most handgun bullets aren't as sharp as rifle bullets, you just need to slow them down so they don't penetrate your skin. The foam metal layer is the body armor's shock absorber for the higher energy bullets that require hard armor to stop. The expanding structure of the metal foam transfers collision energy far less efficiently than solid components. In the area of impact, the foam easily conforms to the impacting object. This plastic deformation locally absorbs mechanical energy. In either case, very little of the collision energy is absorbed by the solid. Some people also choose to add a third layer behind the soft armor, which is called a trauma pad. This is a pad made up of layers of non-Newtonian fluid and padding. It further mitigates the impact of bullet impact on the wearer.
