Mechanical properties of pentaerythritol tetranitrate(PETN) single crystals from nano‐indentation: Depth dependent response at the nano meter scale

Abstract

The current work presents the results from an investigation of the mechanical behavior of single crystals of the energetic material pentaerythritol tetranitrate (PETN) using a nano‐indentation technique. The indentation tests have been performed on the maximum growth habit face (110) of the PETN, using a spherical, Berkovich and an anisometric (wedge‐shaped) tip. The load displacement curves along with analysis have been used to extract the mechanical properties and identify the anisotropic indentation modulus for the PETN. The indentation moduli of the PETN single crystal were found to decrease as indentation depth increases and become independent of indentation depth for depths greater than 200 nm for the spherical indenter and 300 nm for the anisometric wedge indenter and Berkovich tip. The indentation modulus obtained from spherical tip indentation is compared with the results calculated by using literature values of the elastic constants. The wedge indenter measurements and Berkovich indentation at various tip orientations are different due to the anisotropy of the PETN. The yield behaviors of the PETN single crystal were also explored using both spherical and wedge tip indentation and the differences are discussed.