Dynamic behavior and damping capacity of auxetic foam pads

Abstract

A novel set of auxetic (negative Poisson's ratio) open cell polyurethane foam has been developed and tested under dynamic loading conditions to assess the viscoelastic response under white noise random excitation and compressive cycling. Foam pads normalized to standard ISO 13753 have been tested at room temperature and frequency bandwidth 10-500 Hz to assess transmissibility characteristics for possible antivibration glove applications. The results show that the ISO 13753 normalized transmissibility for these foams falls below 0.6 above 100 Hz, with lower peak maximum stresses under indentation compared to conventional open cell solids. These results suggest possible use of the auxetic foam for pads or linens against « white fingers« vibration applications. Further tests have been conducted on cyclic compressive loading up to 3 Hz and loading ratios of 0.95 for loading histories up to 100000 cycles. The damping capacity of the auxetic foams showed and increase by a factor 10 compared to the conventional foams used to manufacture the negative Poisson's ratio ones, and stiffness degradation stabilized after few tens on cycles. [4]. The large number of applications is related to the peculiar deformation mechanisms of auxetic configurations. In fact, and auxetic (negative Poisson's ratio) materials expand in all directions when pulled in only one, leading to an unusual volume change of the solid itself. The negative Poisson's ratio behaviour does not contradict the classical theory of elasticity. A homogeneous, isotropic, thermodynamically correct 3D solid has a potential Poisson's ratio range between -1.0 and 0.5, while the magnitude of the Poisson's ratio can be even larger in the case of anisotropic solids. The dynamic behaviour of auxetic materials has been investigated by several authors [5,6,7,8]. The possible use of auxetic materials for viscoelastic damping applications has been examined in [9], where biphasic auxetic composite showed loss tangent exceeding lower Voigt limit, and close to Hashin upper bound. In recent papers [10,11] increases in loss factor and storage moduli have been shown for auxetic PU foams manufactured using a modified route from the classical production layout. In the field of vibration absorber pads, testing of antivibration glove cushioning materials has been the subject of several research studies [12,13] which have lead to the establishment ISO standard 13753:1999 [14], which defines a method for measuring the mechanical transmissibility of glove cushioning materials. The method determines the impedance of the material when loaded by a mass providing a compression force equivalent to that found when the material is gripped by the hand. This is done by measuring the transfer function of the mass-loaded material at all the required frequencies. The vibration transmission when loaded by the hand is computed using standard values of hand-arm impedance and the measured values of the material impedance. The impedances used in this International Standard are for the palm of the...

Elastyczne Pianki Auksetyczne - Wytwarzanie, Właściwości I Potencjalne Zastosowania

“…Z przedstawionych na rys. 16 badań tłumienności pianki (wg ISO 13753) wynika, że przy czę-stotliwościach w zakresie 10÷31,5 Hz pianki auksetyczne nie wykazują właściwo-ści tłumiących drgania, natomiast w zakresie częstotliwości powyżej 31,5 Hz zdolność do tłumienia drgań zależy od objętościowego współczynnika kompresji zastosowanego przy wytwarzaniu pianki auksetycznej [17]. Niższe wartości tłu-mienności drgań osiągnięto przy mniejszych współczynnikach kompresji objęto-ściowej, np.…”

“…16. Tłumienność drgań próbek o różnych współczynnikach kompresji objętościowej [17] Pianki poddane wstępnemu ściskaniu, z ujemnym współczynnikiem Poissona, wykazują większą zdolność do tłumienia drgań niż pianki w stanie wyjścio-wym, szczególnie dla większych poziomów odkształceń.…”

Metamaterial computation and fabrication of auxetic patterns for architecture.

“…In literature, auxetic structures are classified into several macro groups: re-entrant structures, chiral structures, rotating rigid units, angle-ply laminates, molecular auxetic structures, polymer models, origami-like structures and others (Mir, 2014). Scientific literature already tackled the topic of 3D origami-like auxetics and their potential applications in lightweight architectural structures (Schenk, 2010). Our research, on the other hand, focuses on twodimensional auxetics whose architectural potentialities have not been yet fully explored.…”

On the Damped Beams with Hysteresis

“…We determine the best form for ( ) cx ξ − so that the variation of the energy loss per unit volume with respect to the number of compressive cyclic loadings is the closest to the experimental data [36,37]. The polyurethane sample is obtained from cylinders having the diameter of 30 mm and length of 170 mm.…”

“…In the auxetic materials the shear modulus is significantly greater then the elastic Young modulus It is well known that all major classes of materials (polymers, composites, metals and ceramics) can exist in auxetic form. A specific feature exhibeted by auxetic materials in comparison with other foams is their significant damping capacity at various loading levels, with increase up to 16 times compared to conventional foams [11][12][13]. The size-dependent theories of the damping capacity of auxetic foams have received increasing attention in recent years due to the need to model and analyse very small-sized mechanical interactions inn the rapid developments of micro-nanotechnologies [14][15][16].…”