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Highly tunable bandgaps of phononic crystals are of great significance in practical engineering applications. Solid-liquid transitions and graphene reinforcement are two efficient strategies to manipulate material properties, but their potential to enable bandgap tunability remains rarely explored. This study introduces phase-change materials with solid–liquid transition into phononic crystals containing graphene-reinforced composites to investigate their variation of dispersion features at different temperatures. Theoretical models of the present phononic crystals are formulated and solved by the state space approach and the transfer matrix method. Using published experimental data, the prediction models for the mechanical properties of the phase-change materials under continuous variation of temperature are established, based on which dispersion curves of graphene-reinforced phononic crystals featuring either single or double phase-change materials are depicted and discussed. A comprehensive study is conducted to analyze the effects of the filling fraction of phase-change materials and the volume fraction of graphene fillers in the composites on the thermal control of bandgaps in the structures. The results indicate that the solidification/liquidation of phase-change materials, related to temperature control, can greatly broaden/narrow the bandwidth of the bandgaps in the present structures. A switch-like behavior for the first bandgap, characterized by an open-close-open process as the temperature increases from −25 °C to 15 °C and then to 75 °C, can be achieved by introducing double phase-change materials into the structures. The results of this study explore the potential of graphene-reinforced composites and solid–liquid phase transitions in the design of high-performance tunable phononic crystals.
Guo et al. (Fri,) studied this question.