| About this Abstract |
| Meeting |
2025 TMS Annual Meeting & Exhibition
|
| Symposium
|
Structure-Property Relationships in Molecular Crystal Deformation
|
| Presentation Title |
The onset of plasticity in molecular crystals during contact loading |
| Author(s) |
David F. Bahr, Hugh Grennan, Morgan Chamberlain |
| On-Site Speaker (Planned) |
David F. Bahr |
| Abstract Scope |
Complex bonding in molecular organic crystals leads to materials where dislocations may be hard to make but easy to move, or hard to move and easy to make. Experimental studies in energetic and pharmaceutical systems find that the yield point phenomena appears when the maximum applied shear stress reaches between 2-7% of the elastic modulus of the material. The activation volume does not directly correspond to crystallography across a broad range of space groups, suggesting that dislocation nucleation in molecular crystals exhibits more complicated behavior than in maximum stress models used for atomistic processes (e.g., nucleation in metallic or ionic systems). The activation of plasticity processes in energetic molecular crystals can be directly correlated to defect density, but these defects are not the sole contributors to subsequent dislocation motion. Unlike in many metals, larger tips appear to require larger, not smaller, shear stresses to initiate plasticity. |
| Proceedings Inclusion? |
Planned: |
| Keywords |
Characterization, Mechanical Properties, |