A new theoretical-experimental model deriving from the contactless measurement of the thickness of bulge-tested elastomeric samples

In this paper, an ultrasound measurement method was applied to bulge test on carbon black-filled SBR specimens, in order to determine their thickness at the top of the dome. This method consists in measuring first the variation in the ultrasonic velocity as a function of the deformation in the uniaxial state and subsequently obtaining the thickness value in the equibiaxial state, assuming the congruence of velocity in uniaxial and equibiaxial stress states, respectively. The comparison between experimental data and the thickness values deriving from the most reliable theoretical criteria for both metallic and rubbers-like materials was shown. A new theoretical approach taking into account the slight compressibility of elastomers to estimate the thickness at the dome apex was proposed. Such an approach provided a general equation to define the thickness of the dome in bulge-tested SBR+20Ë as a function of the Poisson ratio.