Experimental survey of the strain energy density function of isoprene rubber vulcanizate

Abstract

An experimental survey of the strain energy density function of an isoprene rubber vulcanízate is carried out by biaxial extension of a sheet specimen. The first derivatives of the strain energy density function with respect to Ix and I2 are obtained from the biaxial stress-strain measurement, where Ix and 12 are the first and the second invariants of Green's deformation tensor, respectively. The measurement of these derivatives is done over a wide range of biaxial deformation, 3.005 < Ix < 20 and 3.005 < I2< 90, in the temperature range 273-353 K. Special care has been taken with the stress and strain measurements in the relatively small deformation region in order to prevent error in the derived values of the derivatives of the strain energy density function. From the result, it is concluded that the strain energy density function should be given by the sum of the two separate terms: W = CT(IX -3) + 6(IXJ2). It has been found that both 9ß/ and ßß/3 2 are more sensitive to changes in I2 than in Ix and the value of ß( ^accounts for, in the case of Ix = I2 = 10, for example, 32.5% of the whole strain energy density W.

Comparison of Hyperelastic Models for Rubber-Like Materials

“…As mentioned in the introduction, it is now well-established that a unique experiment is not sufficient to characterize a rubber-like material even assuming that it is elastic [59][60][61] . Even if the fitting procedure converges for a given mechanical test, it is not ensured that other loading conditions will be well-reproduced with the same set of parameters.…”

“…The second data set is due to Kawabata et al 59 ; it was obtained using an experimental apparatus for general biaxial extension testing. In terms of stretch ratios, unfilled polyisoprene specimen were stretched from 1.04 to 3.7 in the first direction (λ 1 ) and from 0.52 to 3.1 in the perpendicular direction (λ 2 ).…”

“…This ranking is established in regards with the ability of the models to reproduce two given sets of experimental data, i.e. those of Treloar 14 and Kawabata et al 59 , obtained with two similar unfilled natural rubbers. Nevertheless, considering the various loading conditions covered by these two sets, results can be extended to other elastomers and the following ranking should be seen as a decision tool for engineers who deal with finite element simulation of rubber parts.…”

Experiment Which is Done in Rubber Mechanics

“…Numunenin bir kenarı 5 adet çekme çubuğu ile tahrik edilmiş ve bu çekme çubuklarının uyguladığı toplam kuvvet ise bir yük hücresi vasıtasıyla ölçülmüştür. Kauçuk mekaniğinde önemli çalışmalardan birisi de Kawabata ve arkadaşlarının [34][35][36][37][38][39] Literatürde bu tür deneysel çalışma ilk olarak Boonstra tarafından yapılmıştır [47]. Boonstra, 1950 yılına kadar kauçuk türü malzemelerin dikdörtgen formda numune kullanarak iki eksenli çekme deneyinin Ariano [20] Çalışmalarının sonunda lineer gerilme-şekil değiştirme bağıntısı kullanılarak yapılan analitik çözümün problemin davranışını modellemeden uzak olduğu buna karşılık araştırmacının kendisi tarafından önerilen şekil değiştirme enerji fonksiyonu kullanılarak yapılan çözümlerin ise kararsız bölge haricinde, deneysel verilerle uyumlu olduğu ifade edilmiştir.…”

An experimentalist's view of the physics of rubber elasticity

“…The biaxial data (k 1 , k 2 , r 1 , and r 2 ) provide a definite basis for determining the true form of F el . Such biaxial experiments with k 1 = k 2 are, however, quite few, 1,3,7,8 despite their significance.…”