Investigation of the Near Surface Mechanical Properties of Ammonium Perchlorate by Nanoindentation

Abstract

The mechanical response of crystalline energetic solids to force loading is known to play a role in thermal decomposition, and also contributes to the overall mechanical behavior of the composite solid propellant. Ammonium perchlorate (AP) is the most widely used crystalline oxidizer.The near surface mechanical properties and mechanical behavior of the two cleaved surfaces of AP {001} and {210} have been investigated using nanoindentation in combination with atomic force microscopy (AFM). Multiple discontinuities in load vs. penetration depth curves were observed in all the indentations. The hardness exhibited the indentation size effect. The measured hardness was higher than the previously reported for deeper Vickers indentations. The average value of the reduced modulus found for the {001} plane was 22.2�1.0GPa and 19.9�1.1GPa for the {210} plane.AFM was used to study the surface topography and identify the probable slip planes responsible for slip step formation around indentations.