Impact behaviour of 3D printed cellular structures for mouthguard applications

Abstract

Ethylene-Vinyl Acetate (EVA) is the most popular material for manufacturing mouthguards. However, EVA mouthguards are problematic, for example inconsistent thicknesses across the mouthguard. Additive manufacturing provides a promising solution to this problem, as it can manufacture mouthguards with a greater precision. This paper compares the energy dissipation of EVA, the current material used for mouthguards, to various designs of a 3D printed material, some of which contain air cells. Impact testing was carried out at three different strain rates. The Split-Hopkinson bar was used for medium and high strain rate tests, and an Instron test rig was used for low strain rate testing. The best performing design dissipated 25% more energy than EVA in the medium and high strain rate testing respectively while the low strain rate testing was inconclusive. This research has shown that additive manufacturing provides a viable method of manufacturing mouthguards. This opens up the opportunity for embedding electronics/sensors into additive manufactured mouthguards.

Figure 1

Overview of potential mouthguard designs with specimen representations, cross sections of CAD drawings and 3D printed specimens.

Figure 2

Graphical illustration of (a) the Split Hopkinson Pressure bar setup and (b) the Instron 8854 testing setup.

Figure 3

Representative Kirana high speed images of one high strain rate experiment where specimen diameter is; within bar diameter (left), equal to bar diameter (middle) and greater than bar diameter.

Figure 4

True stress-strain curves of investigated specimen configurations for different velocities.

Figure 5

Average dissipated energy and specific dissipated energy with standard deviation by each specimen configuration at different strain rates.

Figure 6

Overview of specimens before testing and after testing for three different strain rates.