This paper describes a strain tester that stretches a knitted fabric or other low-modulus material such that the strain at any point in the specimen is uniform in any planar direction. Radial strain is produced by expanding the perimeter of a circular sample radially. Uniform radial strain is of interest in testing the effects of chemical or other treatments on knitted materials which undergo minimal yarn-loop sliding during use. The apparatus is attachable to a standard tensile tester which records the cumulative stress-strain curve. Force-deformation curves and unrecovered-strain data are given for three patterned jersey knits.
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