Comparative Low-Velocity Impact Response of Sandwich Panels with 3D-Printed PLA Lattice and Bonded XPS Foam Core Systems

Sandwich panels are widely used where high specific stiffness and impact tolerance are required. However, published comparisons of core systems are often confounded by differences in base material, relative density, specimen size, interface condition, manufacturing route, and test protocol. This exploratory study compares three complete sandwich panel core systems under common nominal low-velocity impact conditions: an integrated FDM-printed PLA hexagonal honeycomb, an integrated FDM-printed PLA re-entrant lattice, and an extruded polystyrene (XPS) foam core adhesively bonded between printed PLA face sheets. All panels had identical nominal external dimensions (108 × 100 × 30 mm) and the same nominal PLA face-sheet geometry. The two cellular configurations were produced by fused deposition modelling (FDM) using identical reported printing parameters, whereas the XPS core was adhesively bonded between the printed PLA face sheets. Instrumented drop-weight tests were performed on an Instron CEAST 9450 drop tower, following the principles of ASTM D3763 with modifications for the sandwich panel geometry and available instrumentation, at nominal impact energies of 2.8 J and 11 J. Among the individual specimens tested, the honeycomb configuration produced the highest representative peak contact forces (2008 N at 2.8 J and 3387 N at 11 J). The re-entrant configuration produced the highest mass-normalized criterion-limited work at 11 J (0.0553 J/g), while the bonded XPS configuration produced the lowest and smoothest recorded force response. The work metric was evaluated only up to a representative force criterion and is not interpreted as complete irreversible energy absorption. The comparison provides a preliminary engineering reference for the tested panel systems, but it does not isolate core topology independently from core material, relative density, manufacturing route, or interface condition. Because the integration endpoint is specimen-specific, the work values are descriptive metrics of the individual records rather than directly comparable measures of total energy-absorption performance; repeatability, uncertainty, confidence intervals, and statistical significance are not established.