Structural Integrity and Mechanical Characterization of Novel Lightweight Bio-Inspired Composite Sandwich Panels Additively Manufactured Using Multi Jet Fusion

This study investigates the mechanical performance of novel bio-inspired sandwich structures subjected to quasi-static out-of-plane compression. Lightweight corrugated cores were fabricated via Multi Jet Fusion (MJF) using PA12 reinforced with 40 wt% glass beads. The design was inspired by the natural geometry of oak tree cupules and balsa wood face sheets. A comprehensive experimental campaign examined the influence of key geometric parameters, corrugation height, diameter, and wall thickness, on compressive behavior. All bio-inspired specimens significantly outperformed the bio-based reference panel (BioCom) in terms of maximum compressive load (MCL), absorbed energy (E), and specific absorbed energy (SAE). The best-performing design, Bio-Ins 1, exhibited a fourfold increase in MCL and an eightfold increase in energy absorption, with SAE more than doubled relative to BioCom. Increasing corrugation height led to a 75% gain in peak load and a twofold increase in SAE. Enlarging core diameter doubled the peak load and improved total energy absorption by a factor of 2.75, while increased wall thickness contributed an additional 10% rise in load capacity and a 36% increase in energy absorption. Failure analysis identified a five-stage progressive deformation sequence: initial delamination and micro-cracking, plastic buckling with radial bulging, mixed-mode cracking, extensive core crushing, and final fragmentation. These results demonstrate that mechanical response is governed primarily by architectural parameters rather than material composition. This work highlights the effectiveness of geometry-driven design in developing energy-absorbing, lightweight sandwich panels for advanced structural applications.