Article
Engineering, Mechanical
Qicheng Zhang, Fabrizio Scarpa, David Barton, Yunpeng Zhu, Zi-Qiang Lang, Dayi Zhang, Hua-Xin Peng
Summary: This study describes large strain quasi-static and impact tests of a new class of low-cost uniaxially thermoformed transverse isotropic auxetic foams. The results show that these foams only exhibit auxetic behavior when loaded along the transverse direction to the uniaxial thermoforming compression. The impact energy absorption performance of the foams is enhanced, and the Poisson's ratio approaches 0 at large strains.
INTERNATIONAL JOURNAL OF IMPACT ENGINEERING
(2022)
Article
Mechanics
Zian Jia, Fan Liu, Ling Li, Lifeng Wang
Summary: This study investigates the mechanical properties, instability, and elastic wave isolation behavior of hollow sphere foams (HSFs). By developing explicit formulas and parametric maps, HSFs with desired anisotropic properties can be designed. The study reveals tailorable mechanical anisotropy and band gap in HSFs, and develops a general approach to investigate the direction-dependent properties of periodic materials.
COMPOSITE STRUCTURES
(2022)
Article
Construction & Building Technology
Mohammad Asad, Tatheer Zahra, David P. Thambiratnam, Tommy H. T. Chan, Yan Zhuge
Summary: This paper presents a method for designing and inserting geometrically modified auxetic foam structures in the hollow cores of block masonry walls to mitigate the adverse effects of vehicular impacts. The finite element models of geometrically modified auxetic foams developed in this study show a significant reduction in displacement and change in failure mechanism of masonry walls under high-velocity lateral impacts, contributing to safer masonry buildings along busy road fronts.
CONSTRUCTION AND BUILDING MATERIALS
(2021)
Article
Engineering, Multidisciplinary
Qicheng Zhang, Xindi Yu, Fabrizio Scarpa, David Barton, Kathryn Rankin, Zi-Qiang Lang, Dayi Zhang
Summary: This study investigates the influence of the anisotropy of the foam material on the performance of auxetic foams produced through thermoforming. The results show that the anisotropic nature of the baseline foam plays a significant role in determining the mechanical behavior of the thermoformed auxetic foams. The study also demonstrates that significant negative Poisson's ratios can be achieved in certain conditions, where the foam is thermoformed in specific directions and loaded along a particular axis.
COMPOSITES PART B-ENGINEERING
(2022)
Article
Polymer Science
Xiao Yuan Chen, Ouassim Hamdi, Denis Rodrigue
Summary: This study proposes a method to convert polyethylene foams into auxetic materials with negative Poisson's ratios, which improves their mechanical properties and energy absorption ability. By optimizing the processing conditions, low-density foams with negative Poisson's ratios were obtained. These foams can be used in various applications including sport and military protection equipment.
POLYMERS FOR ADVANCED TECHNOLOGIES
(2023)
Article
Engineering, Chemical
Xiao Yuan Chen, Denis Rodrigue
Summary: This study aims to convert low-density polystyrene (PS) foams into low-density foams with negative tensile and compressive Poisson's ratios through a simple and environmentally friendly process. The resulting auxetic foams have improved mechanical properties compared to the original PS foam and can be used in various applications.
POLYMER ENGINEERING AND SCIENCE
(2023)
Article
Instruments & Instrumentation
Olly Duncan, Andrew Alderson, Tom Allen
Summary: The study developed a method to fabricate auxetic closed cell foam using steam processing, controlling cell structure to produce intentionally anisotropic and gradient foam. This foam demonstrated high impact energy absorption, suitable for footwear, prosthetics, and helmets.
SMART MATERIALS AND STRUCTURES
(2021)
Article
Engineering, Chemical
Zahra Nazari, Hamed Ahmadi, Gholamhossein Liaghat, Samireh Vahid
Summary: This article investigates the impact of fabrication process parameters on the microstructure and compression behavior of polyurethane auxetic foam. The results show that the auxeticity of the foam can be maximized through specific processing conditions and leads to increased energy absorption capabilities.
POLYMER ENGINEERING AND SCIENCE
(2022)
Review
Engineering, Multidisciplinary
Wei Jiang, Xin Ren, Shi Long Wang, Xue Gang Zhang, Xing Yu Zhang, Chen Luo, Yi Min Xie, Fabrizio Scarpa, Andrew Alderson, Ken E. Evans
Summary: Auxetic foams exhibit unique mechanical properties and multiphysics characteristics, making them potential candidates for applications in biomedicine, aerospace, and smart sensing. However, challenges such as complex fabrication and lacking stability hinder their practical applications, requiring further research and development to overcome these barriers.
COMPOSITES PART B-ENGINEERING
(2022)
Article
Materials Science, Composites
Tehseen Ullah, Muzzamal Hussain, Mumtaz Ali, Muhammad Umair
Summary: 3D woven composites are widely used in high-tech applications due to their superior mechanical properties. Auxetic structures can further enhance their mechanical performance. This study developed and tested three types of 3D woven auxetic structures with thermoplastic resins as reinforcement. It was found that the warp interlock structure exhibited the highest auxeticity and mechanical strength compared to the bidirectional interlock structure.
POLYMER COMPOSITES
(2023)
Article
Engineering, Mechanical
Qicheng Zhang, Xindi Yu, Fabrizio Scarpa, David Barton, Yuying Xia, Alexander Shaw, Yunpeng Zhu, Zi-Qiang Lang
Summary: This work investigates the experiments and models of auxetic foams under low-frequency and variable amplitude 3-point bending loading. A custom test rig is designed for dynamic testing of auxetic PU foam, and different cutting orientations and thermoforming compression ratios are tested and compared. The results show that the dynamic modulus of the foams increases with compression ratio, while the dynamic loss factor is minimally affected. Auxetic PU foam exhibits amplitude-dependent stiffness and loss factors.
NONLINEAR DYNAMICS
(2023)
Article
Polymer Science
Chaithanya V. Vinay, D. S. Mohan Varma, Mohammed R. Chandan, Ponsubha Sivabalan, Amit K. Jaiswal, Sai Swetha, Alina Sionkowska, Beata Kaczmarek
Summary: This study focused on the mechanical and antibacterial properties of auxetic polyurethane (APU) foams synthesized using castor oil, showing that the addition of castor oil improved the foams' performance. Castor oil-based APU (CO-APU) foams exhibited higher compression strength and storage modulus, indicating their potential as a better alternative to conventional PU foams for wheelchair seat cushions and hospital bed applications.
POLYMER INTERNATIONAL
(2021)
Article
Materials Science, Multidisciplinary
Lamei Du, Sida Luo, Ye Xu
Summary: Through investigating PU foams with different compression treatments, it is found that Poisson's ratio decreases with compression amount but maximum strain increases, with nonlinear mechanical behaviors related to rib bending in auxetic foams.
MECHANICS OF MATERIALS
(2022)
Article
Mechanics
Qiang Gao, Zhe Ding, Wei-Hsin Liao
Summary: This paper presents an analytical framework to predict the in-plane mechanical properties and proposes a modification coefficient to revise the analytical model. A finite element code is developed to validate the revised model. The results show that the irregularity has a significant effect on the effective Young's modulus but a minor effect on the Poisson's ratio.
COMPOSITE STRUCTURES
(2022)
Article
Engineering, Mechanical
Wanli Xu, Pibo Ma, Liwei Wu, Gaoming Jiang
Summary: This study found that the impact resistance and energy absorption ability of composite materials increase with an increase in the auxetic effect of reinforcement, and composites with better auxetic effect show lower damage levels after low-velocity impact. However, higher initial impact energy can weaken the impact resistance ability of the composites.
JOURNAL OF SANDWICH STRUCTURES & MATERIALS
(2021)
Article
Instruments & Instrumentation
Olly Duncan, Tom Allen, Alana Birch, Leon Foster, John Hart, Andrew Alderson
Summary: This study explored a novel method using steam absorption, cooling, and condensation to convert closed-cell foam into open-cell auxetic foam with a negative Poisson's ratio. Results showed that the final volume ratio of the foam increased with heating time, leading to an increase in re-entrant cell walls and a decrease in compressive Young's modulus. Poisson's ratios were as low as -0.3 in tension and -1.1 in compression, demonstrating the unique mechanical properties of the converted foam.
SMART MATERIALS AND STRUCTURES
(2021)
Article
Instruments & Instrumentation
Olly Duncan, Andrew Alderson, Tom Allen
Summary: The study developed a method to fabricate auxetic closed cell foam using steam processing, controlling cell structure to produce intentionally anisotropic and gradient foam. This foam demonstrated high impact energy absorption, suitable for footwear, prosthetics, and helmets.
SMART MATERIALS AND STRUCTURES
(2021)
Article
Multidisciplinary Sciences
Teik-Cheng Lim
Summary: Inspired by the Maltese cross, a metamaterial capable of exhibiting both positive and negative coefficients of moisture and thermal expansion is presented, while also demonstrating auxetic properties. Effective models for moisture and thermal expansion coefficients were developed through a combination of rotational and translational motions.
ROYAL SOCIETY OPEN SCIENCE
(2021)
Editorial Material
Multidisciplinary Sciences
Teik-Cheng Lim
Article
Physics, Condensed Matter
Teik-Cheng Lim
Summary: In this study, an auxetic metamaterial based on a semirotation system is designed by combining rigid units of two different shapes. The on-axes Poisson's ratios for both infinitesimal and finite deformations are obtained through geometrical consideration. The on-axes Young's moduli are established by matching the spring potential energy and the strain energy of deformation. The results demonstrate the interlacing effect of the shape descriptor, original separation angles, and change in separation angle on the on-axes Poisson's ratio and Young's modulus.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2022)
Article
Multidisciplinary Sciences
Teik-Cheng Lim
Summary: In this study, a controllable metamaterial with positive and negative thermal and hygroscopic expansions is investigated, inspired by Islamic geometric patterns. By constructing from eight pairs of pin-jointed Y-elements, the unit cell of the metamaterial ranges from an eight-pointed star to a regular octagon. The effective coefficients of thermal expansion and moisture expansion are found to be controllable by adjusting the geometrical descriptors of the bimaterial spiral spring and the properties of the bimaterial's layers.
Article
Engineering, Multidisciplinary
Teik-Cheng Lim
Summary: This paper explores a new type of anisotropic auxetic system composed of rotating rhombi and right triangles, inspired by tangram pieces. The Poisson's ratio is obtained through geometric analysis of the representative unit with prescribed boundary requirements. By assigning rotational stiffness to the hinges, the Young's modulus is determined by matching the potential energy stored in the spiral springs with the strain energy of the deformation for the homogenized continuum. The results show that the on-axes Poisson's ratio and dimensionless Young's moduli are determined by the shapes and separation angles of the rigid units, which in turn determine the size of the representative unit of the metamaterial.
ENGINEERING RESEARCH EXPRESS
(2023)
Article
Mechanics
Teik-Cheng Lim
Summary: A mechanical metamaterial with anomalous thermal expansion and Poisson's ratio is introduced in this study, inspired by the tangram puzzle. The coefficients of thermal expansion and Young's moduli were determined through energy matching and strain energy considerations. The in-plane Poisson's ratio was derived for infinitesimal deformation using engineering strain definition and validated for finite deformation. The results show that this tangram-inspired metamaterial exhibits negative in-plane thermal expansivity, high anisotropy, and a switchable Poisson's ratio. The combined characteristics of this metamaterial allow it to function in unique ways that cannot be achieved by conventional materials or existing metamaterials.
EUROPEAN JOURNAL OF MECHANICS A-SOLIDS
(2023)
Article
Physics, Condensed Matter
Teik-Cheng Lim
Summary: A metamaterial model is designed with rotating parallelograms and triangles, in which the Poisson's ratio and Young's moduli can be controlled by changing the internal angles. The model exhibits auxetic behavior for small and large angles, and non-auxetic behavior for intermediate angles. It has the advantage of convenient adjustment of mechanical properties for different applications.
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS
(2023)
Article
Multidisciplinary Sciences
Teik-Cheng Lim
Summary: This paper introduces two types of metamaterials based on the fragmentation-reconstitution of rotating units, which achieve Poisson's ratio discontinuity at the original state. These metamaterials possess unique properties that cannot be fully achieved by conventional materials or auxiliary materials and metamaterials.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2023)
Article
Mechanics
Teik-Cheng Lim
Summary: In this study, a 2D mechanical metamaterial using a combination of rotating parallelograms and non-rotating rhombi is introduced. The Poisson's ratio and coefficients of thermal expansion are primarily governed by the separation angles between the rigid units, while the effective Young's moduli are proportional to the rotational elastic restraint at the hinges connecting adjacent units. Additionally, charges are incorporated into the rhombi to program the sign of the Poisson's ratio under specific geometrical conditions.
INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES
(2023)
Article
Nanoscience & Nanotechnology
Teik-Cheng Lim
Summary: This article introduces a new metamaterial design that exhibits negative thermal expansion during heating and reverses into positive thermal expansion during cooling. The design is inspired by geometric patterns found at the Alhambra Palace and the Great Mosque of Cordoba and is created using bimetallic strips. The study shows that the effective coefficient of thermal expansion (CTE) of the metamaterial is linearly correlated to the change in temperature.
JOURNAL OF SCIENCE-ADVANCED MATERIALS AND DEVICES
(2022)
Article
Materials Science, Multidisciplinary
Teik-Cheng Lim
Summary: This study introduces a mechanical metamaterial inspired by an Aztec geometric pattern, which exhibits negative thermal expansion and adjustable Poisson's ratio. The properties of the material are strongly influenced by the rotational stiffness and aspect ratio of the rotating units.
OXFORD OPEN MATERIALS SCIENCE
(2022)
Article
Engineering, Multidisciplinary
Teik-Cheng Lim
Summary: A new auxetic microstructure inspired by an Islamic geometric pattern is introduced, achieving a negative Poisson's ratio and global rotation during compression.
ENGINEERING RESEARCH EXPRESS
(2021)
Article
Nanoscience & Nanotechnology
Teik-Cheng Lim
Summary: Metamaterials have been designed with properties that switch between positive and negative coefficients depending on the external environment, inspired by Islamic geometric design. The constructed metamaterial shows linear relation between in-plane expansion coefficients and environmental changes. Additionally, the metamaterial exhibits positive and negative Poisson's ratios in different environmental conditions.
ADVANCED COMPOSITES AND HYBRID MATERIALS
(2021)
