Bioinspired engineering polymers by voxel-based 3D-printing

Abstract

Additive manufacturing (AM) has become an important tool in the product development process as it offers the possibility to produce parts of good geometrical quality within a short period of time, allowing geometrical validations and the visualisation of ideas. Yet the application of AM is often limited due to the poor mechanical properties of AM parts. In the automotive sector for example, there is a high demand for tough AM parts which have an impact strength comparable to industrially moulded thermoplasts. This paper explores the possibility to increase the impact strength of AM parts by combining a stiff, hard and brittle component (VeroWhite Plus in this instance) with a soft, elastomer-like component (TangoBlack Plus) and arranging these on a micro-scale level in form of alternating, chess-pattern voxels. While one material was responsible for maintaining a sufficient stiffness and strength of the resulting composite structure, the other material acted as an obstacle for crack propagation. Varying the edge length of the voxels, it was possible to investigate the influence of the microscopic voxel geometry on the part's macroscopic impact strength. It was shown that the Charpy impact strength could be raised by a factor of eight (from 10.9 kJ/m2 to values between 80 kJ/m2 and 86.1 kJ/m2) compared to the single material. Above a certain voxel edge length the impact strength decreases again. The critical voxel edge length at which this decrease begins was determined. However, the increase in impact strength is accompanied by a decrease in the glass transition temperature.