Quantification of fracture mechanics with digital image correlation guides the infill design of 3D-printed snack bars with modulated flexural properties

The ability to design complex infill patterns is unique for 3D food printing to modulate food texture on top of other factors such as processing parameters and structural porosity. This study systematically investigated the impact of infill designs on the flexural properties of 3D-printed snack bars made from pea ingredients. Three-point bending tests revealed that increasing infill angle from 30 to 90 degree resulted in a larger flexural strength but a smaller flexural elongation of the 3D-printed snack bars. However, crossed layer structures did not improve the flexural properties of the samples. Digital image correlation revealed deformation behaviour and fracture propagation of 3D-printed snack bars during mechanical tests. Using the strain maps generated, the designs of the 3D-printed snack bars were modulated to achieve desired flexural properties. Overall, this study shows that it is feasible to customise 3D-printed food texture while maintaining its total calorie, by modifying the infill design.