Enhancing the fracture resistance of additive manufactured polylactic acid via Morse-code-like architecturing

Abstract

Additively manufactured poly-lactic acid (PLA) suffers from a limited fracture resistance. In this study, a combination of circular hole (dot) and elliptical hole (dash) architectures inspired from the Morse-Code are incorporated into (PLA) through additive manufacturing (AM) to improve their fracture resistance. The circular hole-like (C) features work as crack arrestors and the elliptical hole-like (E) features work as crack deflectors. A combination of simulations and experiments are performed to quantifiably determine the effect of single feature, double features, and other tailored arrangements of these features on the crack driving force and fracture resistance using elastic-plastic fracture mechanics. All the AM architecture systems show a significantly higher fracture resistance compared to the bulk AM PLA. Amongst the various systems tested, both the initiation work of fracture and total work of fracture are found to be the highest for alternative layers of E-C features. A 1172 % increase is observed from initiation to total work of fracture for the EC architecture, which is reflected in the fracture resistance curve (R-curve). This has important applications in the structural integrity and life of biomedical systems made from PLA. The applicability of work of fracture and conventional fracture mechanics for additively manufactured, architected systems with significant crack tip plasticity is also discussed.