Additively manufactured kerf structures: Flexibility, energy absorption, and load-bearing behaviors

Abstract

We introduce a new design of flexible structures that draws inspiration from the kerfing method used in wood shaping. The kerf structures, which consist of top and bottom cells linked by connectors and gaps between cells, enable the construction of freeform geometries. The kerf topology can lead to structural reconfigurations, i.e., connector buckling and densification, under compression and locking mechanism under bending, which contributes to energy absorption and alters stiffness and load bearing of kerf structures as they deform. We investigate the compressive and bending responses of 3D-printed kerf structures through experiments and simulations. We consider two kerf topologies, namely hexagon-triangle and square patterns, printed out of brittle Polylactic Acid (PLA), compliant thermoplastic polyurethane (TPU), and ductile Onyx composite consisting of nylon and carbon fiber. We study the interplay of kerf topology and the mechanical behavior of the material in controlling the flexibility, load-bearing capacity, energy absorption, and bend-locking characteristics. Using brittle PLA with hexagon kerf topology results in high load bearing, energy absorption, and bend-locking due to good load resistance of the connectors, better packing ability of hexagon cells, and high strength of PLA. The use of ductile Onyx composite shows an interplay between connector buckling, densification, and inelastic material deformation, contributing to high energy dissipation and energy absorption, as well as good load bearing. Although no failure occurs in the compliant TPU kerf structures, their high flexibility results in low load bearing and low energy absorption.