Brittle-ductile synergistic compressive behavior of the material-extruded hybrid structure with an embedded rhombicuboctahedron core in additive manufacturing: a preliminary study

In this study, a hybrid structure with an embedded rhombicuboctahedral core was fabricated using a material extrusion process, and its compressive behavior was investigated. Polylactic acid (PLA) was used as a stiff internal core, while thermoplastic copolyester (TPC) served as a compliant matrix. The hybrid structure exhibited a specific compressive strength and mass-normalized energy absorption approximately 1.46 times and 1.74–1.86 times higher than that of the TPC-based cubic structure. While the TPC structure showed a typical plateau behavior associated with progressive collapse, the hybrid structure demonstrated a higher initial stiffness and a continuously increasing stress response with noticeable stress fluctuations due to the sequential yielding of the PLA core. This behavior reflects a brittle–ductile synergistic effect, where the TPC matrix enables energy absorption and the PLA core enhances load-bearing capacity. These findings highlight the potential of multi-material additive manufacturing for designing mechanically efficient hybrid structures.