Design-oriented experimental study of failure behavior in additively manufactured polymer composite sandwich panels with mechanically interlocked face-core joints

Abstract

The structural performance of sandwich panels is strongly influenced by the design of the face-core interface, particularly in additively manufactured systems where joint architecture can be deliberately tailored. This study presents an experimental, design-oriented investigation into the failure behavior of additively manufactured polymer composite sandwich panels. The focus is on the role of face-core joining strategies. Honeycomb-core sandwich specimens were fabricated using fused deposition modeling and assembled via adhesive bonding, monolithic (integrated) fabrication, and mechanically interlocked sliding joints with two groove geometries. Three-point bending tests were conducted to evaluate load-bearing capacity, deformation characteristics, damage evolution, and dominant failure modes under flexural loading. The results demonstrate that interface design governs both the failure mode and structural stability of the sandwich panels. Adhesively bonded specimens failed prematurely due to interfacial debonding, while monolithic specimens exhibited brittle and unstable fracture. In contrast, mechanically interlocked joints enabled controlled load transfer and progressive damage evolution, resulting in improved deformation capacity and delayed collapse. From a design perspective, the 3-2 groove configuration provided a more favorable balance between load capacity and damage tolerance compared to the 4-3 configuration, which may be associated with reduced stress concentration at the groove roots. The influence of core material ductility on failure progression is also discussed. The findings provide experimentally supported design insights for the development of damage-tolerant, adhesive-free sandwich structures fabricated via additive manufacturing.