Abstract
As cellular materials are gaining more ground in the automotive, airplane, and railway industries, the demand for functionally graded metal foams has appeared. In the case of syntactic metal foams, by changing the distribution of the filler material, the properties of the foams can be precisely adjusted according to the desired area of application. Several kinds of graded aluminum matrix syntactic foams (GMSFs) were fabricated with lightweight expanded clay aggregate particles and ceramic hollow spheres as filler materials. Their mechanical properties were observed by modal analysis and compression tests, supplemented with an accurate density determination by computer tomography measurements. The compressive properties were set up on a large scale by adjusting the density by adding specific amounts of Al particles to the filler. Based on the modal analysis results, simple averaging the density of GMSFs produces an inaccurate result in mode shapes and material parameters, so the varying density distributions should be taken into account. By simply varying the distribution of the filler material, we can modify the effective material properties of metal foams to better fit industrial requirements.
Highlights
Depending on whether the pores are sealed or interconnected, we can divide metal foams into open-cell and closed-cell
finite element (FE) simulations showed that the energy absorption capacities of this type of foam, which is smaller on the outside and has a larger pore size on the inside, is up to 24% higher than that of samples with the same mass and uniform pore size [11]
We investigated metal foams with AlSi10MnMg matrix material filled with ceramic hollow spheres (CHSs) and lightweight expanded clay aggregate particles (LECAPs) manufactured by pressure infiltration
Summary
Depending on whether the pores are sealed or interconnected, we can divide metal foams into open-cell and closed-cell. The results show that the six-layer samples manufactured by alternating the two fillers along the longitudinal direction gave the highest plateau stress and energy absorption; radial and random GMFs exhibited superior initial strength; and increasing the number of layers enhanced the mechanical properties of the samples [3,4]. All studies showed that multilayer GMFs are very attractive for energy absorption and passive safety protection because of their ability to distribute the kinetic energy of a collision in a controlled manner, but other mechanical properties, such as the effective modulus of elasticity, are rarely investigated. The contact between the spherical shells and the matrix material of the metal foam affects the level of achieved damping It can result in a significant increase due to micro-slip effects on these inner contact surfaces [14,15]. The main contribution of this paper is in (i) the production of GMSFs with changing densities and (ii) the development of investigation techniques–on the basis of vibration analysis–to measure the effective mechanical properties of the produced GMSFs
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