Project 1: Fracture mechanical analysis of heterogeneous photopolymers for additive manufacturing
Figure: AFM results of a droplet-like (a) and interconnected (b) phase structure
Supervisor: J. Stampfl
Co supervisor: H. Sandtner
PhD student: M.Ahmadi
Objectives: The goal of this PhD project is the development and investigation of methods for providing heterogeneous, 3D-printable photopolymers with thermomechanical properties close to thermoplast like ABS.
In polymer-based additive manufacturing, despite the fact that the amorphous photopolymers offer supreme stiffness, strength, and heat deflection temperature, their low toughness and elongation at break restrict their extensive use in 3D-printing engineering applications. These drawbacks stem from the homogeneous nature of amorphous materials, which limits their resistance to crack propagation and makes them susceptible to break. Eliminating this drawback through appropriate toughening mechanisms can open a broad spectrum of innovative applications for 3D-printed parts. The most relevant approach of toughening compliant with characteristics of photo-curable resins and predefined manufacturing is to create heterogeneity in the bulk polymer without using external instrumentation. This is feasible through a process known as Photopolymerization-Induced Phase Separation (PhIPS), which generates heterogeneity into an initially homogeneous system by enabling marginally or completely incompatible components to diffuse with the polymerization progress. The resulted structures offer adjustable mechanical properties based on the interaction of soft and hard phases so that the established domains are able to dissipate the associated energy of crack propagation and increase toughness and elongation at break without sacrificing strength or stiffness of the material.