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J. Stampfl:
"Tough photopolymers for 3D-printing: Design principles and digital materials";
Keynote Lecture: ESIAM, Trondheim (invited); 09-09-2019 - 09-11-2019.

Additive manufacturing (AM) has developed into a promising technology for various applications and provides advantages over conventional manufacturing methods like casting or milling. Drawback of most commercially available systems are the insufficient mechanical properties and the limited resolution of the printed parts. With industry calling for tougher and stronger materials, especially for engineering applications, we developed a stereolithography (SL) process based on the principal of digital light processing (DLP), combined with direct inkjet printing. With this, we are able to print highly viscous photocureable resins with high resolution and excellent surface quality and mimic the thermo-mechanical properties of natural structures like nacre by jetting thin layers of soft material into a hard matrix. In the first step of the process, a resin is cured in a material vat, forming the matrix of the printed part. In a second step, a high-resolution print head selectively places elastomer droplets onto this previous layer which then are cured during the next stereolithographic step. Those so-formed "digital materials" show promising results regarding enhancement of the thermo-mechanical properties, as first experiments indicate an increase of the strain at break and impact strength by over 50% and 40%, respectively - compared to the plain matrix material.
The presented work will also give an overview about general toughening concepts for polymeric, 3D-printable materials and give insight into the interconnections between the most relevant thermomechanical properties (strength stiffness, toughness, heat deflection temperature) for this class of materials.