Interpenetrating-phase composites (IPCs) are advanced structural materials that can reconcile the mutually exclusive strength, ductility, and energy absorption trade-off of conventional composites, yet synchronously enhancing all three properties remains a long-standing challenge. Herein, PLA scaffolds and PLA/PDMS IPCs were fabricated via 3D printing combined with vacuum impregnation. The Poisson’s ratio of the scaffolds was adjusted by tuning the lattice parameter l 1 / l 0 , and its effect on the mechanical properties of the resulting composites was investigated via finite element simulation and quasi-static compression tests. Results show that infiltrating PDMS into positive Poisson’s ratio PLA scaffolds ( l 1 / l 0 =1.0) improves ductility (strain from 0.1 to 0.4) but reduces strength (from 2.6 MPa to 2.0 MPa). By contrast, PLA/PDMS IPCs with moderately negative Poisson’s ratio (NPR) scaffolds ( l 1 / l 0 =0.5) achieve concurrent high strength (2.6 MPa), high ductility (0.4 strain), and superior energy absorption (specific energy absorption of 0.21 J/g at 0.35 strain). This enhancement arises from the auxetic behavior of 3D NPR scaffolds, which imposes triaxial compression on the polymer matrix and provides extra structural support, while excessive NPR aggravates phase conflict, destabilizes the structure, and degrades mechanical performance. This work highlights the critical role of optimized NPR in IPCs design, demonstrating the strong potential of architectured auxetic composites for high-performance energy-absorbing applications in aerospace and related fields.
Li et al. (Fri,) studied this question.