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Blocked Shape Memory Effect in Negative Poisson's Ratio Polymer Metamaterials
Katarzyna Boba1, Matteo Bianchi1, Greg McCombe1
1Advanced Composites Centre for Innovation and Science (ACCIS), University of Bristol , BS8 1TR Bristol, United Kingdom.
ACS Applied Materials & Interfaces
|July 6, 2016
Summary
Researchers developed new polymer foams with a permanent negative Poisson
Area of Science:
- Materials Science
- Polymer Chemistry
- Mechanics of Materials
Background:
- Traditional negative Poisson's ratio (NPR) foams exhibit a temporary auxetic behavior, reverting to their original shape after reheating.
- This reversibility limits the practical application of conventional auxetic foams in various technological fields.
- Shape memory effects in polymers are typically utilized for reversible shape transformations.
Purpose of the Study:
- To create a novel class of open-cell polymer foams with a permanent negative Poisson's ratio (NPR) behavior.
- To overcome the limitations of temporary auxeticity in existing NPR materials for broader technological applications.
- To investigate the role of shape memory effects in achieving stable auxetic properties in polymer foams.
Main Methods:
- Development of open-cell polyurethane-polyethylene (PU-PE) foams.
- Application of multiple shape memory (mSM) treatments to induce permanent NPR behavior.
- Fixation of the foam's cellular topology through mSM treatments.
- Characterization of mechanical properties, including Poisson's ratio and compressive stress-strain behavior.
Main Results:
- Successfully produced a new class of PU-PE foams exhibiting a permanent negative Poisson's ratio.
- The mSM-NPR foams maintain auxetic properties without reverting to their conventional phase after thermal cycling.
- These foams display Poisson's ratio values comparable to auxetic foams before reheating, but with compressive stress-strain curves similar to conventional foams.
Conclusions:
- Manipulating shape memory effects in polymer microstructures enables the creation of materials with stable, unusual deformation mechanisms.
- The developed mSM-NPR foams offer a permanent auxetic behavior, expanding their potential for advanced technological applications.
- This work demonstrates a novel pathway to engineer materials with fixed topological characteristics and desirable mechanical responses.
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