Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Research on mechanical behaviour of unit cells of strengthened re-entrant honeycomb for anti-collision
ship side structures
Rong Yu1, Shengjie Yu2, Yang Zeng3, 4, Jingxi Liu3, 4
1. Wuxi Institute of Technology, Wuxi 214000，China
2. China Ship Scientific Research Centre, Wuxi 214082, China
3. School of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
4. Hubei Key Laboratory of Naval Architecture and Ocean Engineering Hydrodynamics (HUST),

structure of rods, hinges, and springs. Since then, a plenty of auxetic
topologies with negative Poisson’s ratio have elaborated: re-entrant
topology (Lakes, R 1987), double array topology (Ma, L, 2018), chiral
topology (Jiang, YY, 2017), rotating unit topology ( Grima, JN, 2000 ),random voronoi topology (Gao, RC, 2019), and hybrid topology ( Zhou,L, 2018 ).

ABSTRACT
Mechanical behavior of strengthened re-entrant hexagonal unit cells foranti-collision ship side structures under quasi-static planar compression
was conducted by experimental test and FEA in the present research.
Four types of re-entrant unit cells which are strengthened by narrow rib,curved ribs, rhombic ribs and polyurethane foam were presented. FE
analyses were carried out to simulate the quasi-static compressive tests,
satisfactory agreements were achieved between the FEA andexperimental deformed shapes and load–displacements. Test and FE
results show that the foam filled unit cell has a significant advantage in
specific energy absorption capability. The present investigations provide
useful insight into the strengthened re-entrant hexagonal unit cell, thefoam filled honeycomb lead to excellent load carrying capability andenergy absorption capability as expected, and would be used in thedevelopment of novel light weight energy absorbing honeycomb
structure for ship side anti-collision.

Re-entrant structures of the auxetic structure have recently attracted
considerable attentions due to its simple topology. Lakes (1987) madethe first attempt to fabricate an auxetic porous polyester foam fromconventional low-density open-cell polymer foam by causing the ribs ofeach cell to permanently protrude inward which resulted in a re-entrantstructure, in 1987. Since then, numerous research on fabrication ofauxetic structures with re-entrant topologies have been conducted. As atypical periodic cellular structures, 2D auxetic honeycombs with reentrant topology have been produced by researchers. Ma L (2018)
fabricated a 2-D negative Poisson’s ratio structure with laminatedcomposites by hot-press moulding. Zied (2015) proposed splined
enhanced re-entrant topology, and fabricated with mild steel by laser
additive manufacturing. Wang XT (2016) fabricated 3-D re-entrant
structures by a complicated interlocking assembly method. In recentyears, with the maturity of additive manufacturing technology, additive
manufacturing technique is also used to fabricate complex auxetic
topologies which cannot be fabricated by conventional technology
before. Rahman (2018) fabricated auxetic hierarchical honeycomb bypolymer. Zhang JJ (2018a, 2018b) fabricated typical 2D re-entrant
structures with stainless steel and polymer by 3D printing, and presented
a theoretical analysis method. Wang K (2015) present a 3-D re-entrant
meta-material by 3D-pringting. Lee W (2019) fabricated symmetricauxetic structure by additive manufacturing, and proposed mechanicalbehavior of the structure under axial impact load.

KEY WORDS: Negative Poisson’s ratio; re-entrant hexagonal
honeycomb; foam filled; planar compression test; FEAINTRODUCTION
Negative Poisson’s ratio structures undergo a transverse contraction
when subjected to longitudinal compression, or undergo a lateralexpansion under longitudinal stretching. The word “auxetic” was coined
firstly to describe the microporous polyethylene foam with negative
Poisson’s ratio (Yunan, P, 2012). The so-called auxetic
materials/structures with negative Poisson’s ratio have been discovered
and attracted attentions in the past few decades.
Negative Poisson’s ratio has in fact been found in a wide variety ofnatural materials including zeolite ( Grima, JN, 2000 ) cubic elemental
metal (Ray, H, 1998), and even biological materials such as cow teat skin
(Caroline, L, 1991) and human tendon (Ruben, G, 2015). Meanwhile,
artificial auxetic materials and structures with negative Poisson’s ratio
have been discovered and attracted attentions. Systematic research on
artificial auxetic structure firstly started in 1985 by Almgren (1985). A
re-entrant structural topology was established theoretically by ideal

Generally, the re-entrant structure needs substantial porosity. Due to its
unique structural topology, the stiffness of re-entrant structure is lower
than that of the traditional honeycomb counterparts and the solids fromwhich it is made. Eventually, this causes limitations on the engineering
applications of the re-entrant auxetic structures (Yunan, P, 2012). In
order to improve stiffness and energy absorption capability, new typesof topologies have been conducted. Lu ZX (2016) proposed astrengthened topology base on traditional re-entrant topology by adding

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