TPMS-based hierarchically infilled metamaterials via stress-guided strategy for exceptional thermo-mechanical synergy

Triply periodic minimal surface (TPMS) lattice metamaterials, featuring lightweight characteristics, high load-bearing efficiency, and tailorable heat-transfer responses, show great potential for aerospace structures and thermal management systems. A single topology rarely optimizes load bearing, material efficiency, and thermal response simultaneously, whereas geometry-driven hybridization can place material in regions that contribute little to load bearing. In this study, a field-driven, stress-guided hierarchical infilling strategy is proposed. A hybrid Primitive (P) / I-graph-wrapped package (I-WP) configuration is used as the primary lattice, and small-scale TPMS unit cells, including D, G, and P-type units, are selectively infilled into the targeted low-stress regions of the primary framework. We used the stress map to place 1-mm D, G, or P-type TPMS units in low-stress regions of a P/IWP primary framework and fabricated the resulting hierarchically infilled metamaterials (HIMs) by LPBF. Combined with finite element analysis, quasi-static compression tests, and thermal-response characterization, the effects of volume fraction and infill unit-cell topology on the compressive mechanical properties and thermal insulation/heat dissipation behavior of the HIM structures are systematically evaluated. At a global volume fraction of 28 %, the best-performing HIM design increased elastic modulus by 94.82 %, yield strength by 72.6 %, and CAD-derived surface-area density by 247.56 % relative to PL-28. Mechanistically, stress-guided secondary infilling provides lateral support to the primary framework and reduces normalized stress localization during early collapse, thereby interrupting the development of a continuous diagonal shear band and promoting progressive layer-wise collapse. From the thermal perspective, the complex interconnected porous network and increased specific surface area enhance the thermal-response regulation capability of the structure. The results support stress-guided infilling as a controllable route for balancing mechanical performance and surface thermal response in TPMS lattices.