Manufacturing Thermoset Lattice Core Sandwich Panel via Frontal Polymerization

Frontal polymerization (FP) is a promising polymer curing technique leveraging a self-propagating exothermic polymerization reaction front to rapidly and fully cure monomers into thermoset polymers upon initiation. Prior studies have demonstrated the feasibility of using this propagating reaction front in a direct-ink writing (DIW) setting for both free-form and layer-by-layer printing of polymer and composite structures. In this study, FP-based DIW is adopted to develop a manufacturing technique for thermoset lattice core sandwich panels (LCSPs) that eliminates the need for additional bonding steps between the lattice core and face sheets. Different types of lattice cores are first printed by using FP-based DIW, where an IR camera is used to monitor the front behavior and adjust the front velocity in real time to improve printing accuracy. Face sheets are subsequently fabricated and bonded to the lattice core by immersing the lattice core into a reservoir of ink and initiating FP, which eliminates the need for bonding typically seen in LCSP manufacturing. The fabricated panels are examined using an optical microscope, and compressive tests are conducted by using parts fabricated by fused deposition modeling (FDM) as a reference. The printed parts show reasonable dimensional accuracy and full bonding between the face sheet and lattice core without visible air bubbles or voids, to the precision of the microscope. The DCPD LCSPs have a much higher ultimate strength compared to that of their FDM counterparts.