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Evolution of Shore Hardness under Uniaxial Tension/Compression in Body-Temperature Programmable Elastic Shape Memory
Balasundaram Selvan Naveen1, Nivya Theresa Jose2, Pranav Krishnan3
1School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Polymers
|November 26, 2022
Summary
Body-temperature programmable elastic shape memory hybrids exhibit significant softening under cyclic loading. Hardness changes after programming are linked to micro-gap formation, with recovery upon heating.
Area of Science:
- Materials Science
- Polymer Science
- Biomaterials Engineering
Background:
- Elastic shape memory hybrids (SMHs) programmable at body temperature offer potential for comfortable wearable devices.
- Shore hardness is a standard metric for characterizing elastic materials, crucial for understanding material behavior under stress.
Purpose of the Study:
- To systematically investigate the evolution of shore hardness in body-temperature programmable elastic SMHs.
- To analyze hardness changes during cyclic loading and shape memory cycles.
- To elucidate the mechanisms behind observed hardness variations.
Main Methods:
- Characterization of elastic shape memory hybrids using shore hardness measurements.
- Application of cyclic loading to induce mechanical stress and strain.
- Programming of shape memory effects at body temperature.
- Analysis of hardness changes post-programming and post-cyclic loading.
Main Results:
- Cyclic loading above a critical strain induces significant softening, akin to the Mullins effect.
- Hardness generally increases with programming strain, but some surfaces show an initial decrease followed by a rapid increase.
- Micro-gap formation between inclusion and matrix explains the anomalous hardness decrease after programming.
- Heating to melt inclusions leads to substantial recovery of original hardness in all tested samples.
Conclusions:
- The shore hardness of body-temperature programmable elastic SMHs is sensitive to both cyclic loading and programming conditions.
- Understanding hardness evolution is key to optimizing SMHs for wearable applications.
- The observed phenomena are mechanistically explained by material deformation and microstructural changes, reversible upon heating.
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