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Author

C Lira

Other affiliations: Bristol and Bath Science Park
Bio: C Lira is an academic researcher from University of Bristol. The author has contributed to research in topics: Honeycomb structure & Honeycomb. The author has an hindex of 11, co-authored 15 publications receiving 664 citations. Previous affiliations of C Lira include Bristol and Bath Science Park.

Papers
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Journal ArticleDOI
TL;DR: In this article, a vibroacoustics analysis of auxetic gradient honeycomb composite structures with hexagonal configurations is presented, where two classes of gradient cellular layout are examined: one with continuously varying internal cell angle, the other with gradient cell wall aspect ratio across the surface of the honeycomb panel.

135 citations

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TL;DR: In this paper, the authors describe the transverse shear stiffness of a novel topology of gradient honeycomb structures, where the tessellation of the cells is not periodic, but is dictated by geometric constraints between adjacent units.

119 citations

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TL;DR: In this article, the bending and failure behavior of polymorphic honeycomb topologies consisting of gradient variations of the horizontal rib length and cell internal across the surface of the cellular structures was described.
Abstract: We describe the bending and failure behaviour of polymorphic honeycomb topologies consisting of gradient variations of the horizontal rib length and cell internal across the surface of the cellular structures. The novel cores were used to manufacture sandwich beams subjected to three-point bending tests. Full-scale nonlinear Finite Element models were also developed to simulate the flexural and failure behaviour of the sandwich structures. Good agreement was observed between the experimental and FE model results. And the validated numerical model was then used to perform a parametric analysis on the influence of the gradient core geometry over the mechanical performance of the structures. It was found that the aspect ratio and the extent of gradient (i.e. the horizontal rib length growth rate or the internal angle increment) have a significant influence on the flexural properties of the sandwich panels with angle gradient cores.

116 citations

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TL;DR: In this paper, gradient cellular centresymmetric auxetic configurations are evaluated as potential cores for aeroengine fan blades, and optimized to reduce the dynamic response for the first three fundamental modes.
Abstract: In this study, gradient cellular centresymmetric auxetic configurations are evaluated as potential cores for aeroengine fan blades, and optimized to reduce the dynamic response for the first three fundamental modes. Auxetic (negative Poisson’s ratio) re-entrant cellular beams are modeled, manufactured, and tested to assess their natural frequencies and mode shapes. Gradient versions of these beams with a varying internal cell angle are then designed to be incorporated as fillers in a baseline fan blade model. The optimized configurations of the gradient core lead to a substantial decrease of the mass of the fan blade, reduction of the dynamic modal displacements, and a lowering of the first three natural frequencies within the admissible frequency bandwidth.

115 citations

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TL;DR: In this article, the transverse shear properties of a centersymmetric honeycomb structure evaluated using analytical and finite element models are described. But the analytical models are validated using a full scale Finite Element technique to simulate transverseShear tests, a quarter FE of the RVE with periodic shear conditions and an FE homogenisation method for periodic structures.

91 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the relationship among structures, materials, properties and applications of auxetic metamaterials and structures is discussed. And the challenges and future work on the topic of auxetics are also presented to inspire prospective research work.
Abstract: Materials and structures with negative Poisson's ratio exhibit a counter-intuitive behaviour. Under uniaxial compression (tension), these materials and structures contract (expand) transversely. The materials and structures that possess this feature are also termed as 'auxetics'. Many desirable properties resulting from this uncommon behaviour are reported. These superior properties offer auxetics broad potential applications in the fields of smart filters, sensors, medical devices and protective equipment. However, there are still challenging problems which impede a wider application of auxetic materials. This review paper mainly focuses on the relationships among structures, materials, properties and applications of auxetic metamaterials and structures. The previous works of auxetics are extensively reviewed, including different auxetic cellular models, naturally observed auxetic behaviour, different desirable properties of auxetics, and potential applications. In particular, metallic auxetic materials and a methodology for generating 3D metallic auxetic materials are reviewed in details. Although most of the literature mentions that auxetic materials possess superior properties, very few types of auxetic materials have been fabricated and implemented for practical applications. Here, the challenges and future work on the topic of auxetics are also presented to inspire prospective research work. This review article covers the most recent progress of auxetic metamaterials and auxetic structures. More importantly, several drawbacks of auxetics are also presented to caution researchers in the future study.

603 citations

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TL;DR: In this paper, the authors summarized research work related to materials with zero, or negative Poisson's ratio, referred to as auxetic materials, and predicted that future research will be in the direction of disordered microstructures utilizing the homogenization method.

483 citations

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TL;DR: In this article, the authors focus on the topology-property relationship in three main classes of auxetic metamaterials, namely re-entrant, chiral, and rotating (semi-) rigid structures.
Abstract: The surge of interest in so-called “designer materials” during the last few years together with recent advances in additive manufacturing (3D printing) techniques that enable fabrication of materials with arbitrarily complex nano/micro-architecture have attracted increasing attention to the concept of mechanical metamaterials. Owing to their rationally designed nano/micro-architecture, mechanical metamaterials exhibit unusual properties at the macro-scale. These unusual mechanical properties could be exploited for the development of materials with advanced functionalities, with applications in soft robotics, biomedicine, soft electronics, acoustic cloaking, etc. Auxetic mechanical metamaterials are identified by a negative Poisson's ratio and are perhaps the most widely studied type of mechanical metamaterials. Similar to other types of mechanical metamaterials, the negative Poisson's ratio of auxetics is generally a direct consequence of the topology of their nano/micro-architecture. This paper therefore focuses on the topology–property relationship in three main classes of auxetic metamaterials, namely re-entrant, chiral, and rotating (semi-) rigid structures. While the deformation mechanisms in the above-mentioned types of structures and their relationship with the large-scale mechanical properties receive most attention, the emerging concepts in design of auxetics such as the use of instability in soft matter and origami-based structures are discussed as well. Furthermore, the data available in the literature regarding the elastic properties of auxetic mechanical metamaterials are systematically analyzed to identify the spread of Young's modulus–Poisson's ratio duos achieved in the auxetic materials developed to date.

428 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive updated review of auxetic materials, their types and properties, and applications has been presented, and the design and modeling approaches of Auxetic structures are discussed.
Abstract: Material properties can be tailored through modification of their geometry or architecture. With this concept, a lot of smart materials, metamaterials, and smart structures have been developed. Auxetic materials and structures are a novel class of materials which exhibit an interesting property of negative Poisson's ratio. By virtue of the auxetic behavior, mechanical properties such as fracture toughness, indentation resistance, etc., can be improved. In order to exploit the interesting properties of auxetic materials, several potential applications of auxetic materials have been explored in medical, sports, automobile, defense, etc. Design and modeling of novel auxetic materials and structures is still on the way. Here, the article focuses upon the different aspects of auxetic materials and structures. A comprehensive updated review of auxetic materials, their types and properties, and applications has been presented. This paper also discusses the design and modeling approaches of auxetic structures.

378 citations

Journal ArticleDOI
TL;DR: In this paper, an analytical model of a 3D reentrant honeycomb auxetic cellular structure has been established based on both a large deflection beam model and a Timoshenko beam model.

367 citations