Pomelo Peel-Inspired 3D-Printed Porous Structure for Efficient Absorption of Compressive Strain Energy

Abstract

The porous structure in pomelo peel is believed to be responsible for the protection of its fruit from damage during the free falling from a tree. The quantitative understanding of the relationship between the deformation behavior and the porous structure could pave the way for the design of porous structures for efficient energy absorption. Here, a universal feature of pore distribution in pomelo peels along the radial direction is extracted from three varieties of pomelos, which shows strong correlation to the deformation behavior of the peels under compression. Guided by the porous design found in pomelo peels, porous polyether-ether-ketone (PEEK) cube is additively manufactured and possesses the highest ability to absorb energy during compression as compared to the non-pomelo-inspired geometries, which is further confirmed by the finite element simulation. The nature-optimized porous structure revealed here could guide the design of lightweight and high-energy-dissipating materials/devices.

Functional Anatomy, Impact Behavior and Energy Dissipation of the Peel of Citrus × limon: A Comparison of Citrus × limon and Citrus maxima

“…The results of this study show that the peel of Citrus × limon has very high energy dissipation capabilities, which are similar to the ones previously reported for the peel of Citrus maxima [ 3 , 19 ], although the gradation of the albedo, the sample thickness, the transmitted force and impact duration differ significantly ( Section 2 ). The structures of both fruits can be described as sandwich structures, with a graded foam core in technical terms.…”

“…Furthermore, the cell density begins to increase in the flavedo again ( Figure 3 ). Yang et al [ 19 ] describe a similar decrease in the cell distribution of different varieties of Citrus maxima . They also observed an increase in the cell density towards the epidermis, but they divided the peel into coarser steps (20% steps) and did not describe the increase in higher spatial resolution and detail.…”

“…Citrus maxima compensates for the less graded transition in the peel with its thicker peel and its less densely arranged albedo. The peculiarities of the peel structure are also the reason why Citrus maxima achieves a very high energy dissipation [ 19 ]. The difference of Citrus × limon is probably due to the fact that the fruit is derived from a species cross, and it has been bred intensively [ 5 , 8 ].…”

“…The peel of pomelo ( Citrus maxima ) has already been examined in detail: free fall tests with whole fruits and tensile tests with peel samples were carried out [ 12 ]. Additionally, drop-weight tests of peel samples [ 3 ], compression tests with peel samples have been performed [ 2 ] and the peel structure of different varieties of pomelo have been compared [ 19 ]. Internal strain mapping (X-ray tomographic imaging and digital volume correlation) has been made via in-situ stepwise uniaxial compression tests of peel samples [ 20 ], and the viscoelastic behavior of the peel has been characterized by mathematical models [ 1 ].…”

“…First replicas of the peel structure on silica have been made [ 21 ], and pomelo-inspired metallic foams [ 12 ] and composites have been designed [ 22 , 23 ]. Moreover, there are initial additively manufactured porous polymer cubes inspired by the pomelo peel [ 19 ].…”