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.