Indentation of an Oriented Transparent Polyamide

In this study, the effect of orientation on the indentation hardness and energy absorption of an oriented transparent Trogamid polyamide was investigated with a spherical indentation methodology. It was found that the orientation significantly improved the indentation hardness and energy absorbed by plastic deformation. From the indentation hardness measurement, the elastic modulus, yield stress, and strain hardening exponent were derived from both the elastic and plastic regions of the indentation load-displacement curves. The elastic modulus Was found to remain the same with orientation; the yield stress and the strain hardening exponent increased with orientation. The increase in the strain hardening exponent was the primary reason for the improved indentation hardness and energy absorption in the oriented samples. The mechanical properties from indentation measurements were compared to values obtained from tension true stress/true strain measurements. Good agreement was observed between the results from the indentation and tension tests. The effect of temperature oil the mechanical properties was also studied. It was found that the modulus and yield stress were higher at a lower temperature; however, the strain hardening exponent remained unaffected. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 112: 163-172, 2009