The determination of Poisson's ratio compliances for polyethylene terephthalate sheets using a Michelson interferometer

Two of the Poisson's ratio compliances have been determined for oriented polyethylene terephthalate (PET) sheet. The method adopted was to determine the fringe shift under load when the specimens were placed in one arm of a Michelson interferometer operating in a vertical fringe mode. Data obtained for the specimens in air and in a water bath, with two polarization directions, can be used to provide two independent measurements of each compliance. Good agreement was shown between these measurements, and the values for the compliance constants are reasonable on physical grounds, as well as being consistent with previous work on PET fibres.