Errors matter when measuring Poisson's ratio of nearly incompressible elastomers

Poisson's ratio (ν) is a materials property that quantifies the compressibility of a material. Measurements of this property become important for soft elastomers which display nearly incompressible behavior (ν > 0.495). Small differences in this property can lead to large differences in the stresses that develop during hydrostatic loadings such as those observed in gaskets, o-rings, and thin films. While there are multiple methods that can be used to quantify ν, many methods were developed for compressible materials which require less precision than nearly incompressible materials. Here an experimental survey of three methods of characterizing ν of a nearly incompressible elastomer is performed. These methods include direct measurement via digital image correlation, indirect measurement from the bulk modulus and Young's modulus, and a recently proposed method of indirect measurement from the shear modulus and Young's modulus. Particular care is paid towards understanding how experimental errors impact both the precision and accuracy of each method. It is found that indirectly measuring ν from the bulk modulus and Young's modulus is the most appropriate method for distinguishing nearly incompressible behavior from the incompressible limit (ν = 0.5).