Title: Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity

Abstract

Assessing the mechanical behavior (elastic properties, plastic properties, and fracture phenomena) of molecular crystals is often complicated by the difficulty in preparing samples. Pharmaceuticals and energetic materials in particular are often used in composite structures or tablets, where the individual grains can strongly impact the solid behavior. Nanoindentation is a convenient method to experimentally assess these properties, and it is used here to demonstrate the similarity in the mechanical properties of two distinct systems: individual crystals of the explosive cyclotetramethylene tetranitramine (HMX) and the pharmaceutical idoxuridine were tested in their as-precipitated state, and the effective average modulus and hardness (which can be orientation dependent) were determined. Both exhibit a hardness of 1.0 GPa, with an effective reduced modulus of 25 and 23 GPa for the HMX and idoxuridine, respectively. They also exhibit similar yield point behavior. This indicates idoxuridine may be a suitable mechanical surrogate (or “mock”) for HMX. While the methodology to assess elastic and plastic properties was relatively insensitive to specific crystal orientation (i.e., a uniform distribution in properties was observed for all random crystals tested), the indentation-induced fracture properties appear to be much more sensitive to tip-crystal orientation, and an unloading slope analysis is used to demonstratemore » the need for further refinement in relating toughness to orientation in these materials with relatively complex slip systems and crystal structures. View Full-Text« less

Authors:

Burch, Alexandra ^[1]; Yeager, John ^[2]; Bahr, David ^[1]

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+ Show Author Affiliations

1. Purdue Univ., West Lafayette, IN (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Publication Date:

2017-11-01

Research Org.:

Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1412909

Report Number(s):

LA-UR-17-28625
Journal ID: ISSN 2073-4352; CRYSBC

Grant/Contract Number:  

AC52-06NA25396

Resource Type:

Accepted Manuscript

Journal Name:

Crystals

Additional Journal Information:

Journal Volume: 7; Journal Issue: 11; Journal ID: ISSN 2073-4352

Publisher:

MDPI

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE