Digital Light Processing of 2D Lattice Composites for Tunable Self-Sensing and Mechanical Performance

Abstract

This study investigates the mechanical and piezoresistive self-sensing performance of additive manufacturing-enabled 2D nanocomposite lattices under monotonic and cyclic tensile loading. Lattice structures comprising hexagonal, chiral, triangular, and reentrant unit cell topologies are realized via digital light processing using an acrylic photocurable resin filled with carbon nanotubes (CNTs). The results reveal that the piezoresistive sensitivity of reentrant and triangular lattices is nearly insensitive to changes in relative density. In contrast, the gauge factors of the hexagonal and chiral lattices rise by 300% and 500%, respectively, with an increase in relative density from 20 to 40%, which can be ascribed to their bend-dominated behavior, causing an increase in surface strains in the lattice struts with increasing relative density for an imposed macroscopic strain. The measured stress versus strain responses compare well with nonlinear finite element results. Under strain-controlled cyclic loading, the electrical resistance of the 2D lattices is found to decline over time due to reorientation of the CNTs in the surrounding viscoelastic polymer matrix. The findings provide valuable insights into the interrelations between sensing performance, cell architecture, and relative density of the lattices, and offer guidelines for the design of architected strain sensors and self-sensing lightweight structures.