Thermal management of electronic devices remains a challenging issue, especially the cooling of electronic components. Current methods mostly involve noisy, cumbersome and underperforming fans. It has recently been shown that phase change materials (PCMs) can perform better and offer more efficient damping of temperature variations in electronic components. Here, we present three novel contributions. First, we consider a triplyperiodic minimal surface, called a gyroid, as a porous architectured structure containing the PCM. Such a topology mathematically maximizes the exchange surface between the copper structure and the PCM. Heat transfer and thus the performance of such a composite are therefore optimized. Second, we set up a complete 3D coupled fluid-structure model of the composite. This model simulates the heat transfer (conduction and convection) inside both the PCM and the porous structure, as well as the mechanical stresses induced on the container by thermal expansion of the PCM. The 3D coupled theoretical model is based on open-source software codes, OpenFOAM, CalculiX and preCICE. With this novel model, deformation of the structure and mechanical stresses are now predictable. It is therefore possible to anticipate whether a configuration will be prone to leakage due to mechanical failure. Thermal contact resistance is also computed, giving information on heat transfer quality at the interface between the composite and the electronic component. Third, the application of this model to the innovative composite shows that reducing the initial filling level of PCM is a better solution than strengthening the container to maximize thermal management.