scholarly journals The Impact of Technology on Poisson’s Ratio of Auxetic Polyurethane Foams

2018 ◽  
Vol 41 (1) ◽  
pp. 119-160
Author(s):  
Janusz Lisiecki ◽  
Dominik Nowakowski
Keyword(s):  
Polyurethane Foam ◽  
Air Force ◽  
Poisson’S Ratio ◽  
Polyurethane Foams ◽  
Poisson's Ratio ◽  
Institute Of Technology ◽  
Impact Of Technology ◽  
The Impact

Abstract The article presents a method for measuring Poisson’s ratio of the polyurethane foam, including shapes of the auxetic foam. The impact of technology applied in Air Force Institute of Technology, that is a method for processing the selected polyurethane foams, on the value of Poisson’s ratio of the auxetic foam shape was presented. In order to manufacture the auxetic foam shapes, two methods; mechanical-thermal and mechanical-chemical-thermal, were applied.

scholarly journals Sandwich panel with in-plane honeycombs in different Poisson's ratio under low to medium impact loads

2021 ◽  
Vol 60 (1) ◽  
pp. 145-157
Author(s):  
Yi Luo ◽  
Ke Yuan ◽  
Lumin Shen ◽  
Jiefu Liu
Keyword(s):  
Poisson’S Ratio ◽  
Sandwich Panel ◽  
Impact Force ◽  
Impact Resistance ◽  
Poisson's Ratio ◽  
Compression Performance ◽  
Post Impact ◽  
Local Impact ◽  
Collapse Behavior ◽  
The Impact

Abstract In this study, a series of in-plane hexagonal honeycombs with different Poisson's ratio induced by topological diversity are studied, considering re-entrant, semi-re-entrant and convex cells, respectively. The crushing strength of honeycomb in terms of Poisson's ratio is firstly presented. In the previous research, we have studied the compression performance of honeycomb with different negative Poisson's ratio. In this study, a comparative study on the local impact resistance of different sandwich panels is conducted by considering a spherical projectile with low to medium impact speed. Some critical criteria (i.e. local indentation profile, global deflection, impact force and energy absorption) are adopted to analyze the impact resistance. Finally, an influential mechanism of Poisson's ratio on the local impact resistance of sandwich panel is studied by considering the variation of core strength and post-impact collapse behavior.

Polyurethane Foam with a Negative Poisson's Ratio for Diabetic Shoes

2005 ◽  
pp. 677-0
Author(s):  
K.O. Park ◽  
Jong Chul Park ◽  
Jae Boong Choi ◽  
Sung Jae Lee ◽  
H.H. Choi ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Negative Poisson’S Ratio ◽  
Negative Poisson's Ratio

scholarly journals 4D Printing of NiTi Auxetic Structure with Improved Ballistic Performance

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 745
Author(s):  
Hany Hassanin ◽  
Alessandro Abena ◽  
Mahmoud Ahmed Elsayed ◽  
Khamis Essa
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Analytical Model ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
4D Printing ◽  
Auxetic Structures ◽  
Negative Poisson's Ratio ◽  
The Impact ◽  
Auxetic Structure

Auxetic structures have attracted attention in energy absorption applications owing to their improved shear modulus and enhanced resistance to indentation. On the other hand, four-dimensional (4D) printing is an emerging technology that is capable of 3D printing smart materials with additional functionality. This paper introduces the development of a NiTi negative-Poisson’s-ratio structure with superelasticity/shape memory capabilities for improved ballistic applications. An analytical model was initially used to optimize the geometrical parameters of a re-entrant auxetic structure. It was found that the re-entrant auxetic structure with a cell angle of −30° produced the highest Poisson’s ratio of −2.089. The 4D printing process using a powder bed fusion system was used to fabricate the optimized NiTi auxetic structure. The measured negative Poisson’s ratio of the fabricated auxetic structure was found in agreement with both the analytical model and the finite element simulation. A finite element model was developed to simulate the dynamic response of the optimized auxetic NiTi structure subjected to different projectile speeds. Three stages of the impact process describing the penetration of the top plate, auxetic structure, and bottom plate have been identified. The results show that the optimized auxetic structures affect the dynamic response of the projectile by getting denser toward the impact location. This helped to improve the energy absorbed per unit mass of the NiTi auxetic structure to about two times higher than that of the solid NiTi plate and five times higher than that of the solid conventional steel plate.

scholarly journals High Partial Auxeticity Induced by Nanochannels in [111]-Direction in a Simple Model with Yukawa Interactions

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2550 ◽  
Author(s):  
Konstantin Tretiakov ◽  
Paweł Pigłowski ◽  
Jakub Narojczyk ◽  
Mikołaj Bilski ◽  
Krzysztof Wojciechowski
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Poisson’S Ratio ◽  
Yukawa Potential ◽  
Poisson's Ratio ◽  
Debye Screening Length ◽  
Debye Screening ◽  
Screening Length ◽  
Narrow Channels ◽  
The Impact

Computer simulations using Monte Carlo method in the isobaric-isothermal ensemble were used to investigate the impact of nanoinclusions in the form of very narrow channels in the [ 111 ] -direction on elastic properties of crystals, whose particles interact via Yukawa potential. The studies were performed for several selected values of Debye screening length ( ( κ σ ) − 1 ). It has been observed that introduction of the nanoinclusions into the system reduces the negative value of Poisson’s ratio towards [ 110 ] [ 1 1 ¯ 0 ] , maintaining practically constant values of Poisson’s ratio in the directions [ 100 ] and [ 111 ] . These studies also show that concentration of particles forming the nanoinclusions in the system has a significant effect on the value of Poisson’s ratio in the [ 110 ] [ 1 1 ¯ 0 ] -direction. A strong (more than fourfold) decrease of Poisson’s ratio in this direction was observed, from − 0.147 ( 3 ) (system without inclusions) to − 0.614 ( 14 ) (system with nanoinclusions) at κ σ = 10 when the inclusion particles constituted about 10 percent of all particles. The research also showed an increase in the degree of auxeticity in the system with increasing concentration of nanoinclusion particles for all the screening lengths considered.

Mechanical Properties of Thin Film Silicon Carbide

2001 ◽  
Vol 687 ◽  
Author(s):  
Kamili M. Jackson ◽  
Richard L. Edwards ◽  
Guy F. Dirras ◽  
William N. Sharpe
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Massachusetts Institute Of Technology ◽  
Preliminary Results ◽  
High Temperature Electronics ◽  
Microtensile Testing ◽  
Institute Of Technology

AbstractSilicon carbide is a very attractive material for a variety of applications. Originally considered for use in high power and high temperature electronics because of its large bandgap, designers of MEMS are now considering use of silicon carbide because of its stability at high temperatures, resistance to corrosives, high stiffness, and radiation resistance. However, as with any new structural material, its mechanical properties must be measured for design information. This research measures the elastic modulus, strength, and Poisson's ratio of two different silicon carbides using microtensile testing. One material is a 0.5-1νm thick film from Case Western Reserve University. Preliminary results give an average of 420 GPa for elastic modulus, a strength of 1.2 GPa, and a Poisson's ratio of 0.19. The second material is from Massachusetts Institute of Technology with an average thickness of 30 microns. Preliminary results show an elastic modulus of 430 GPa, a strength of 0.49 GPa, and a Poisson's ratio of 0.24. In addition to the most recent results, techniques used to obtain these results, microstructure investigations, and a comparison of the materials are detailed.

Exploring the impact of hydrostatic pressure on the structural, electronic and mechanical properties of ZrNiPb half-Heusler alloy: A DFT approach

2018 ◽  
Vol 32 (23) ◽  
pp. 1850248
Author(s):  
M. I. Babalola ◽  
B. I. Adetunji ◽  
B. E. Iyorzor ◽  
A. Yaya
Keyword(s):  
Mechanical Properties ◽  
Heusler Alloy ◽  
Poisson’S Ratio ◽  
Density Functional ◽  
Energy Gap ◽  
Poisson's Ratio ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Impact

The structural, electronic, elastic and mechanical properties of ZrNiPb half-Heusler alloy under pressure ranging from 0 to 25 GPa have been studied using the density functional theory within the generalized gradient approximation (GGA). The results of ambient condition were in good agreement with the available theoretical and experimental data. Our electronic structure and density of state results show that ZrNiPb is an indirect bandgap semiconductor half-Heusler alloy with a narrow energy gap of 0.375 eV. Based on the calculated elastic constants (C[Formula: see text], C[Formula: see text] and C[Formula: see text]), Young’s modulus (E), Poisson’s ratio ([Formula: see text]), Shear modulus (G), Zener anisotropy factor (A) and brittle-ductile behaviors under pressure have been discussed. The calculated Poisson’s ratio shows that ZrNiPb undergoes a relatively small volume change during uniaxial deformation. We show that the chemical bonds in ZrNiPb are stronger due to the high value of C[Formula: see text].

An Application of the Interferometer Strain Gage in Photoelasticity

1935 ◽  
Vol 2 (3) ◽  
pp. A99-A102
Author(s):  
R. W. Vose
Keyword(s):  
Strain Gage ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Massachusetts Institute ◽  
Massachusetts Institute Of Technology ◽  
Lateral Deformation ◽  
Principal Stresses ◽  
Photoelastic Analysis ◽  
The Difference ◽  
Institute Of Technology

Abstract This paper was written at the suggestion of Mr. Mieth Maeser, in response to numerous inquiries concerning the methods of photoelastic analysis in use at the Massachusetts Institute of Technology. By the use of any of the usual photoelastic methods the difference of the principal stresses and their direction at any point in a suitable loaded specimen are determined, and through a knowledge of Poisson’s ratio their sum is obtained (and a solution made possible) by a measurement of the lateral deformation of the specimen by means of an interferometer strain gage. This instrument, together with its accessories and their use, is illustrated and described in the paper. Examples of the problems solved by the use of the instrument show its accuracy and the consistency of the results obtained by the method.

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