Following high profile, life changing long term mental illnesses and fatalities in sports such as skiing, cricket and American football—sports injuries feature regularly in national and international news. A mismatch between equipment certification tests, user expectations and infield falls and collisions is thought to affect risk perception, increasing the prevalence and severity of injuries. Auxetic foams, structures and textiles have been suggested for application to sporting goods, particularly protective equipment, due to their unique form-fitting deformation and curvature, high energy absorption and high indentation resistance. The purpose of this critical review is to communicate how auxetics could be useful to sports equipment (with a focus on injury prevention), and clearly lay out the steps required to realise their expected benefits. Initial overviews of auxetic materials and sporting protective equipment are followed by a description of common auxetic materials and structures, and how to produce them in foams, textiles and Additively Manufactured structures. Beneficial characteristics, limitations and commercial prospects are discussed, leading to a consideration of possible further work required to realise potential uses (such as in personal protective equipment and highly conformable garments).

https://www.mdpi.com/2076-3417/8/6/941/pdf

Review of Auxetic Materials for Sports Applications: Expanding Options in Comfort and Protection

Auxetic cellular solids in the forms of honeycombs under blast load have great potential in a diverse range of applications, including core material in sandwich plates composite components. Based o...

Nonlinear dynamic response and vibration of sandwich composite plates with negative Poisson’s ratio in auxetic honeycombs:

This paper reviews 2D auxetic models, including 3D deformation models with 2D auxetic behavior, from mechanism perspective instead of geometrical perspective. On this basis, auxetic models across different geometrical groups can be regrouped into clusters that exhibit analogy in deformation mechanism. Factors that are taken into consideration include the identification of corresponding (i) rotation and non-rotation units, as well as (ii) linkages/joints between rotation and non-rotation units and non-linkages/non-joints across various auxetic models. As a result, five clusters of auxetic models have been identified, in which auxetic models within each cluster are analogous to each other. The identified clusters are those that exhibit: (a) double periodicity in the rotation direction of their rotating units, (b) synchronized rotation direction of their rotation units, (c) single periodicity in the rotation direction of their rotating units, (d) random rotation of their rotation units, and (e) non-rotation of units. Results from this analogy identification place auxetic models in a systematic representation and will enrich future development of auxetic models, particularly those that do not fall within these five clusters. It is proposed that future work includes 3D auxetic models as well as ordering of analogous auxetic models according to their joints or linkage geometries.

Analogies across auxetic models based on deformation mechanism

New approach to investigate nonlinear dynamic response of sandwich auxetic double curves shallow shells using TSDT

Effective properties and dynamic response of a sandwich panel made of two face sheets and auxetic core are analyzed in this study by computer simulations. The inner composite layer is made of a cellular auxetic structure immersed in a filler material of a given Poisson's ratio (filler material fills the voids in structure). Each cell is composed of an auxetic structure (re-entrant honeycomb or rotating square), i.e., exhibiting negative Poisson's ratio without any filler. Influence of filler material on the effective properties of the sandwich panel is investigated. The proposed structure shows interesting structural characteristics and dynamic properties. Our results clearly show that it is possible to create auxetic sandwich panels made of two solid materials with positive Poisson's ratio. This is even possible if the filler material is nearly incompressible, but can move in out-of-plane direction. Moreover, effective Young's modulus of such sandwich panels becomes very large if the Poisson's ratio of the filler material tends to −1.

Dynamic response of sandwich panels with auxetic cores

A sandwich-structured composite is a special class of composite materials that is fabricated by attaching two thin but stiff layers to a lightweight but thick core Composites analyzed in this paper consist of two different materials: auxetic and structural steel The optimization criterion is minimum compliance for the load case where the frame's top boundary is downward loaded Outer layers are made of steel while the middle layer is two-phase solid material composite Only the middle layer is optimized by means of minimization of the objective function defined as the internal strain energy In the first part of this paper we study the application of the solid isotropic material with penalization (SIMP) model to find the optimal distribution of a given amount of materials in sandwich-structured composite In the second part we propose a multilayered composite structure in which internal layers surfaces are wavy In both cases the total energy strain is analyzed

Computational analysis of sandwich‐structured composites with an auxetic phase

This paper presents modelling and a FEM analysis of dynamic properties of a thermally optimal two-phase composite structure. Simulations were provided for 2D models. At the first step, topology optimization was performed, where an internal energy was minimized. At the second step, analysis of dynamic properties was executed. Calculations allowed to determine eigenfrequencies and the mode shape of the structure. Solid isotropic material with penalization (SIMP) model was used to find the optimal solution. The optimization algorithm was based on SNOPT method and Finite Element Method.

Finite Element Analysis of Dynamic Properties o f Thermally Optimal Two - Phase Composite Structure

Topology optimization of the effective thermal properties of two-phase composites

Due to the fact that modern materials are widely used in aerospace industry, automotive industry, medicine and many others it is very important to find out a way to meet all its needful parameters. There is a lot of composites, which arise from a combination of at least two different components on the macroscopic level and whose parameters are unknown. Therefore, it is difficult to get to know their possibilities and functionality. A kind of composite materials are Functionally Graded Materials (FGM). They are characterized by the fact that its composition and structure gradually change over the volume, which follows from changes in properties of material (Miyamoto et al., 1999). There are many works on this topic.

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Maria Nienartowicz

Papers

Dynamic response of sandwich panels with auxetic cores

Computational analysis of sandwich‐structured composites with an auxetic phase

Finite Element Analysis of Dynamic Properties o f Thermally Optimal Two - Phase Composite Structure

Topology optimization of the effective thermal properties of two-phase composites

Identification of Thermal Conductivity of Modern Materials Using the Finite Element Method and Nelder-Mead's Optimization Algorithm