Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity
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 ind...
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| Format: | Article |
| Language: | English |
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MDPI AG
2017-11-01
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| Series: | Crystals |
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| Online Access: | https://www.mdpi.com/2073-4352/7/11/335 |
| _version_ | 1797999398909640704 |
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| author | Alexandra C. Burch John D. Yeager David F. Bahr |
| author_facet | Alexandra C. Burch John D. Yeager David F. Bahr |
| author_sort | Alexandra C. Burch |
| collection | DOAJ |
| description | 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 demonstrate the need for further refinement in relating toughness to orientation in these materials with relatively complex slip systems and crystal structures. |
| first_indexed | 2024-04-11T11:04:03Z |
| format | Article |
| id | doaj.art-56b7b95bfe4140f9b6b9a7bb256213e1 |
| institution | Directory Open Access Journal |
| issn | 2073-4352 |
| language | English |
| last_indexed | 2024-04-11T11:04:03Z |
| publishDate | 2017-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Crystals |
| spelling | doaj.art-56b7b95bfe4140f9b6b9a7bb256213e12022-12-22T04:28:26ZengMDPI AGCrystals2073-43522017-11-0171133510.3390/cryst7110335cryst7110335Nanoindentation of HMX and Idoxuridine to Determine Mechanical SimilarityAlexandra C. Burch0John D. Yeager1David F. Bahr2School of Materials Engineering, Purdue University, West Lafayette, IN 47907, USAExplosive Science and Shock Physics, Los Alamos National Laboratory, Los Alamos, NM 87545, USASchool of Materials Engineering, Purdue University, West Lafayette, IN 47907, USAAssessing 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 demonstrate the need for further refinement in relating toughness to orientation in these materials with relatively complex slip systems and crystal structures.https://www.mdpi.com/2073-4352/7/11/335nanoindentationmolecular crystalsmechanical propertieshardnesselastic modulusfracture |
| spellingShingle | Alexandra C. Burch John D. Yeager David F. Bahr Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity Crystals nanoindentation molecular crystals mechanical properties hardness elastic modulus fracture |
| title | Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity |
| title_full | Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity |
| title_fullStr | Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity |
| title_full_unstemmed | Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity |
| title_short | Nanoindentation of HMX and Idoxuridine to Determine Mechanical Similarity |
| title_sort | nanoindentation of hmx and idoxuridine to determine mechanical similarity |
| topic | nanoindentation molecular crystals mechanical properties hardness elastic modulus fracture |
| url | https://www.mdpi.com/2073-4352/7/11/335 |
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