Toughening mechanisms in 3D printing: a numerical and experimental study

Abstract

Additive Manufacturing, also known as 3D printing, is a disruptive technology which marked a substantial change in the way products are conceived both in the industrial and academic world. Thanks to this new manufacturing method, tougher components can be created by taking some precautions in the design process. This is true especially when considering one of the latest innovations in 3D printing: the continuous fiber deposition. The aim of this thesis is the study of the main toughening mechanisms that can be adopted when designing a component, whether with continuous fiber reinforcement or not. The first part is dedicated to the analysis of the influence of a continuous fiber reinforcement on the mechanical performance of the specimen, from a numerical standpoint. Experimental results are replicated in a satisfactory way and the effectiveness of the phase field model for fracture in catching the cracking phenomena for 3D printed components is demonstrated. Later, a result-driven optimization is proposed, showing how a simple optimization pipeline is able to provide a better and tougher design, given the component’s geometry and loading conditions. In this case, an anisotropic phase field formulation is adopted and various loading conditions are considered in the analysis, such as tension, shear and bending. In the last part, the toughening mechanisms are investigated experimentally on components manufactured in Onyx. It is demonstrated, through a Three Point Bending testing campaign, that simple modifications of the printing parameters, such as raster angle and stacking direction adopted, can lead to big changes in the mechanical properties of the specimen, always keeping its shape unchanged.