An accurate description of the mechanical behaviour of inhomogeneous, anisotropic composite materials, such as metal matrix syntactic foams (MMSFs), is a challenging task. This paper is based on the so-called substructure technique, which has never been used for the mechanical modelling of metal foams or MMSFs. Using this method, a finite element model with low computational requirements but still modelling inhomogeneous properties can be constructed that reproduces the results of laboratory measurements with high accuracy. In all cases, the tests presented in this paper are limited to the linearly elastic phase. As the most common investigation of MMSFs is the compression test, this study considers only this loading case. A more detailed discussion of the stress analysis of MMSFs is given at the end of this work. A potential cause of 45° crack planes during compression tests and the evolution of stresses as a function of space-filling are also investigated.

The presented work is based on the wave propagation properties of composite metal foams in a two-dimensional model with a focus on the energy absorption. The energy flux method was used for the study and it was shown that composite metal foams have a significant energy absorption capacity. Hence, they can be used with high efficiency, for example, as a sound insulation layer. A pair of materials commonly used in syntactic metal foams, iron shell and aluminium matrix material, was used in the finite element model. Damping is included in the calculations to avoid oscillations.

The presented work focuses on the development of a novel method that can numerically describe the properties of metal matrix syntactic foam (MMSF) with low memory requirements and short computational times without losing the properties of the interior structure. In this paper, we propose a novel method that avoids using the homogenization technique and instead rearranges stiffness matrices and constructs specific substructures to perform the overall construction. The two-dimensional cases are discussed in order to focus on the methodology itself. First, the reductions and structural design with solid mesh structures were performed, and then the model was applied on structures filled with iron hollow spheres. So far, the method has been used to evaluate small deformations to see how suitable the subspace technique is for describing metal foams. Aluminum was used as the matrix material, as it is one of the most common materials for MMSFs. The optimal parameters were searched that resulted in the shortest running time for the given construction. Since in the proposed substructure technique only the displacement values at the boundary points are computed, a back-calculation step for each selected substructure was performed to see the interior deformations in the vicinity of an iron hollow sphere.

Purpose – The accurate characterisation of the dynamic behaviour of inhomogeneous materials is a challenging task. Examples of such materials are composites, which are becoming increasingly common in the industrial world. Wave propagation studies in these materials, which are hard to model, are usually very complicated and difficult or even impossible to generalise to other composites. The authors aim to develop a special, easy-to-use finite element method to investigate wave propagation in any composite in a memory-efficient and accurate way. Design/methodology/approach – The study combines the substructure technique, a method published in the 1970s, with the central difference method (CDM) in a specific way. This can be called as Combined Method (CM). It is important to note that CM and CDM are completely identical in accuracy, as using the substructure technique is only an equation rearrangement. Findings – For metal matrix syntactic foams (MMSFs), it has been shown that CM can significantly decrease the memory requirements of the finite element models without loss of accuracy. Moreover, it greatly reduces the time-consuming construction of large-scale inhomogeneous finite element models. The comparison between the CDM and CM shows that the larger the model in which the wave propagation is investigated, the greater the advantage of CM. Originality/value – The CM methodology is not only applicable to the study of the wave propagation characteristics of MMSFs, but can easily be transferred to the study of other composites.