Mechanical characterisation of Duraform® Flex for FEA hyperelastic material modelling

Laser Sintering (LS) is widely accepted as a leading additive manufacturing process with a proven capability for manufacturing complex lattice structures using a group of specially developed powder based materials. However, to date, very little research has been directed towards achieving greater knowledge of the properties of the elastomeric materials that can be used to produce energy absorbent items such as personalised sports helmets and running shoes via the LS technique. This paper will contribute to addressing this knowledge gap by examining the material properties and characteristics of Duraform® Flex, a commercially available elastomeric material used for such LS applications. A 3D Systems HiQ machine fitted with a closed loop thermal control system was employed, together with a number of the advanced processing options available in the operating software. In order to measure the mechanical properties of this material, sets of ISO standard tensile test specimens were fabricated, employing a range of different manufacturing processing parameters. The result shows that varying key LS processing parameters such as powder bed temperature, laser power and the number of scanning exposures has a significant impact on the mechanical properties of the resulting part, including its ultimate strength and elongation at break. As LS is a layer manufacturing process, part properties are found to vary considerably between the horizontal (X-Y) and vertical (Z) build orientations. The paper demonstrates how the measured tensile stress-strain curve can be transformed into appropriate hyperelastic material models employing the data curve fitting process in PTC Creo 2.0 Simulate software, and how these material models can be used practically to match user requirements for the laser sintered parts, leading to design optimisation for both bulky solid and lightweight lattice components. The paper concludes with a discussion examining the potential future direction of the research