Application of Aluminum Foam Energy-Absorbing Layers in Critical Facility Protection
In practical engineering applications, aluminum foamis rarely used alone as a load-bearing component. Instead, it is embedded in composite sandwich structures as a sacrificial layer or core material. Composite explosion-proof walls containing aluminum Foam energy-absorbing layers typically consist of three parts: a front cover layer, an aluminum foam core layer, and a back main structure.
Steel-Aluminum Foam Sandwich Structure
The steel/aluminum foam/steel "sandwich" structure is currently the most widely used configuration. In this structure, a high-strength steel plate serves as the front cover layer. Its main function is to resist localized penetration from the explosion, intercept high-speed fragments, and evenly distribute point-like or localized impact loads onto a larger area of the aluminum foam core layer. The steel plate has extremely high tensile strength and can absorb some of the initial kinetic energy through the membrane effect.
The stress wave is absorbed by the aluminium foam core layer. When the wall is subjected to the blast shock wave, the front steel plate is displaced towards the interior, compressing the aluminium foam core. The kinetic energy is dissipated by the aluminium foam by cell breakage and collapse. Experimental results indicate that a steel-aluminum foam sandwich panel of 30 mm thickness (a 3 mm steel/24 mm foam/3 mm steel panel) is subjected to less than 23 mm of dynamic deformation under an HG85 grenade threat without any back side fragmentation, which fully demonstrates its structural performance and protective effectiveness. Composite blast walls may be utilized in civilian construction as well as in the most highly classified military installations. The porous structure of aluminum foam creates an energy-absorbing cushion which protects the building and reduces the risk of secondary injuries to personnel and equipment. The growing popularity of drones has made it possible for them to be used to launch suicidal attacks on critical energy facilities like nuclear stations. Aluminum foam composite steel panels are installed as sacrificial layers on top of the concrete walls which are already installed. The first layer is a high strength steel plate which will prevent the explosion from entering a localized area. The next layer is constructed of closed-cell aluminum foam and it absorbs a large percentage (50-70%) of the energy of the explosion by deforming. The maximum stress of the shock wave entering the concrete shell is considerably reduced due to this.
The composite structure is employed in defense of backup diesel generator rooms, control rooms, and spent fuel storages. Facilities in such areas have to be explosion resistant, and bullet and fragment resistant. High speed fragments are efficiently blocked with the foamed aluminum core layer, which minimizes damage to delicate equipment. The fire resistance of the latter (in compliance with DIN EN 45545-2) provides nuclear power plants with supplementary safety redundancy in case of post attack fires.
Military Camps and Transport Containers
Foamed aluminium composite materials are used in the military to make transportable shelters, command centers and containers to carry explosives. According to UN 6A, 6B and 6C standards, containers with foamed aluminum liners are capable of effectively shielding against damage caused by accidental explosion of explosive material inside or protecting explosive and flammable materials inside against external attack.
Experimental results show that explosion-proof doors using foamed aluminum sandwich structures can reduce their weight significantly from 500 kg/m² of traditional concrete doors to 147 kg/m² while maintaining the protection level. This weight reduction is crucial for rapid deployment in the field and the mobility of mechanized forces. Meanwhile, due to the excellent machinability of aluminum foam (it can be drilled, sawed, milled, and welded), protective components can be customized into complex geometries according to site requirements.
The composite explosion-proof wall containing an aluminum foam energy-absorbing layer represents a technological trend in modern protective engineering, shifting from "rigid resistance" to "flexible dissipation." By utilizing the long plateau stress characteristics of aluminum foam, this composite structure can achieve highly efficient attenuation of blast shock waves and high-speed fragments under extremely light weight, protecting the core structure and saving lives.
