3D printed single-material bio-inspired layered structures with mechanical heterogeneity for enhanced energy absorption

Although multi-material 3D printing enables the fabrication of complex bio-inspired layered structures (BILSs) with mechanical heterogeneity to enhance toughness, this approach still faces inherent limitations, particularly regarding material compatibility issues. To overcome this challenge, this study proposes a novel 3D printing strategy for fabricating a single-material BILS (SMBILS) with mechanical heterogeneity because the mechanical properties of a 3D-printed parts are influenced by the printing parameters. Response surface methodology was employed to quantify the correlations between critical printing parameters and key mechanical properties. Subsequently, a multi-objective optimization process was implemented to determine parameter combinations for two printed phases with desired properties (designated as strong and weak phases). The SMBILS was then fabricated by alternate deposition of these two phases. Charpy impact tests and single edge notched bending (SENB) tests demonstrated that, compared to homogeneous single-phase, the impact strength and energy absorption performance of the SMBILSs were enhanced by up to 283 % and 322 %, respectively. Furthermore, strain distribution evolution was captured using digital image correlation (DIC) techniques, while micro-morphological characteristics of fracture were analyzed through scanning electron microscopy (SEM). The enhanced mechanical performance of SMBILS is attributed to the stress state regulation and the modification of crack propagation path. This parameter-modulated single-material strategy achieves controlled mechanical heterogeneity, providing a compatibility-free solution for fabricating bio-inspired composites with enhanced toughness.