Performance-driven design of non-uniform porous infills via multi-material topology optimization

Porous-infill structures have gained prominence in engineering design due to their exceptional capabilities in weight reduction, multifunctionality, and material efficiency. However, conventional design approaches relying on uniform porosity distributions or periodic lattice patterns often fail to adapt to non-uniform stress fields, leading to material redundancy and insufficient structural performance. This study introduces a novel topology optimization framework for multi-phase porous structures, addressing the limitations of existing methods by integrating material heterogeneity, load-driven porosity gradients, and multi-phase interaction principles. Leveraging a mathematically rigorous inverse design paradigm, the proposed framework enables adaptive control of pore connectivity and phase distribution through stress field-guided local density modulation. The optimization process strategically combines rigid, compliant, and porous phases to achieve synergistic material synergies, balancing conflicting objectives such as load-bearing capacity and lightweight. Case studies of cantilever beams illustrate the method's capacity to generate functionally graded architectures featuring redundant load paths and controlled failure mechanisms while maintaining performance integrity. This work advances the field of multi-material topology optimization by providing a systematic methodology for designing lightweight, failure-resistant structures with tailored mechanical and functional properties, offering broad applicability in aerospace, biomedical, and energy-related engineering systems.