Evaluating a Non-Newtonian Shear-Thickening Surface During Fruit Impacts

Abstract

Abstract. The impact parameters critical to fruit damage are peak acceleration and velocity change, and they vary according to material properties and characteristics. Drop tests were conducted using an instrumented sphere to record impact parameters on four surfaces: a tile floor, a human hand, 10 mm thick vinyl foam, and a non-Newtonian shear-thickening fluid composed of cornstarch and water. Drop heights ranged from 0.31 to 1.2 m. At a drop height of 0.31 m, the peak acceleration and velocity change recorded by the instrumented sphere were, respectively, 336 G and 4.3 m s -1 on the tile floor and 50.1 G and 2.3 m s -1 on the non-Newtonian surface. At a drop height of 0.91 m, the maximum peak acceleration and velocity change recorded on the non-Newtonian surface were 140 G and 4.5 m s -1 , compared to 470 G and 6.6 m s -1 on the vinyl foam. ‘Jazz’ apples had a bruise rate of 14% while ‘Pacific Rose’ apples bruised 36% of the time when dropped from 1.2 m onto the non-Newtonian surface. Peach damage was 13%, 10%, and 12% for drop heights of 0.31, 0.61, and 0.91 m, respectively, on the non-Newtonian surface. For pears dropped on the non-Newtonian surface, no damage occurred when dropped from 1.2 m or lower heights, whereas the damage was 5%, graded against U.S. Extra No. 1, for a drop height of 3.3 m. A surface with rheological properties similar to a non-Newtonian shear-thickening fluid can decrease the peak acceleration and velocity change during fruit impacting, thereby maintaining fruit quality.