Full-field characterizations of additively manufactured composite cellular structures

Honeycomb structures possess unique mechanical and structural behaviors, including high specific strength, superior energy absorption, and potential for multifunctionality. The advantages of such structures are bolstered by their realization through additive manufacturing, enabling cellular geometries beyond traditionally fabricated hexagons and facilitating a pathway for hybridization using composite materials to tune the response. This research synthesized photocurable, particulate-reinforced resins using mechanically compliant matrix and glass microballoons reinforcement. The modified resins were used to additively manufacture lattice structures with circular and hexagonal unit cell geometries at different glass microballoons reinforcement weight ratios, ranging from neat to 20 wt.%. The 3D printed structures were tested under quasi-static and impact loading scenarios to elucidate the interrelationships between the cell geometry, induced deformations, and strain rates. The mechanical testing was coupled with digital image correlation (DIC) to reveal the deformation-geometry interrelationship on the global (macroscale) and local (mesoscale) levels. The multiscale analyses allowed for extensive characterization of the effect of cell geometry and increased weight reinforcement on the mechanical response at a global, sub-cellular, and cellular level, i.e., elucidating the hierarchical dependency. The novelty leading to the current study stems from probing and revealing the deformation state of cellular structures subjected to two loading scenarios using DIC. This study intended to provide mechanistic insights for engineering lattice structures for impact mitigation applications by offering a viable approach to additive manufacturing composite materials.