Constructions with integrated aluminium foam are lightweight, absorb energy and dampen vibrations and noises. So far, near-net foam components and three-dimensionally shapeable sandwich structures have been implemented. Now comes the APM technology. With it, the aluminium foams in the form of spheres can be used simply, flexibly and cost-effectively for a variety of products.
Comparing metal foams with polymer foams, they essentially differ only by the metallic matrix material. A metal foam member has a closed surface and a highly porous cellular core (comparable to, for example, human bones). Metal foams can be made in a variety of processes. In the powder metallurgical process route, a metal powder is homogeneously mixed with a propellant powder (example – titanium hydride) and compacted to an expandable precursor of about 98% density. If this starting material is heated to the melting temperature of the metal, the blowing agent releases a gas (example – hydrogen) when heated. Once the metal becomes molten, the gas expands the melt into the liquid metal foam.
Near-net-shape aluminium foam components:
This process can take place in suitable foaming molds so that the expanding metal foam assumes the inner contour of the foaming mold. After cooling, the near-net-shape metal foam component can be removed from the mold. The main applications are lightweight construction, energy absorption, and vibration/noise reduction. For example, by locally introducing an aluminium foam into a car A-pillar, its energy absorption, and thus the passive safety of the vehicle, can be increased by 40%. If lightweight construction is the goal, the sheet thickness of the A-pillar is reduced. The associated loss of energy absorption is compensated by the metal foam core so that the level of passive safety remains constant or slightly increases with overall reduced weight.
An interesting combination of lightweight construction and sound/vibration damping is achieved by the targeted introduction of metal foam segments, example in gears . The structure-borne noise emission of the component is reduced and shifted to other frequency ranges. In a study, steel gears were equipped with aluminium foam segments and subjected to various test runs. Compared to the conventional gearwheel, a weight reduction of up to 30% and a noise reduction of up to 10 dB A could be achieved by integrating the aluminium foam segments. This vibration damping effect of the aluminium foam is also successfully exploited in supporting beams and foundations of machine tools so that in addition to the reduction of noise emission and an increased machining precision is achieved. The SAF aluminum foil of Cymat Technologies for automobiles is used to make the floor of the car, the lining and the sandwich of the door.
Aluminium Foam Sandwich AFS:
Another option for using aluminium foam for lightweight construction is the so-called aluminium foam sandwich AFS (Aluminium Foam Sandwich). In this case, two cover layers of a conventional aluminium alloy are bonded to a middle core layer of expandable aluminium by roll-plating. From this three-layer precursor, composite can be produced with conventional sheet metal forming a complex-shaped sheet metal part. In subsequent heat treatment, the core layer is expanded to aluminium foam.Thus, without increasing the weight, the sheet thickness and thus the moment of inertia of the critical area moment of inertia are multiplied. This material composite, which is ideal for lightweight construction, was installed in a lifting arm holder on a mobile work platform, among other things. So weight could be saved at the main mast of the stage, which was immediately invested in an extended arm again. The mobile platform remains below the weight limit for the driver’s license and has a much greater range compared to the competition.