Evaluation of Young's modulus of polymers from Knoop microindentation tests

The Young's modulus to hardness ratio of small-scale polymer specimens is measured by means of a Knoop indentation procedure. The technique assumes that the extent of elastic recovery of a Knoop indent is linearly related to the modulus to hardness ratio. A semiempirical linear relationship is proposed for the elastic recovery of the small diagonal of a Knoop indenter as a function of the modulus to hardness ratio for polymer materials, provided that indenting loads of at least 4 N are used. The major benefit of the procedure is that measurements of Knoop microhardness and indentation recovery enable the evaluation of Young's modulus of small-scale polymer specimens. (C) 1998 Elsevier Science Ltd. All rights reserved.