We review Treloar's biaxial experiments and Kearsley's calculated instability in a square rubber sheet. Treloar's rubber is recognized as a Mooney-Rivlin material. It turns out that Treloar's test could not have anticipated Kearsley's stability analysis, since his loads were far below the critical load of bifurcation. We repeat Treloar's experiment but with much higher loads and confirm Kearsley's prediction.
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