Torsion and bistability of double-twist elastomers

We investigate the elastic properties of anisotropic elastomers with a double-twist director field, which is a model for collagen fibrils or blue phases. We observe a significant Poynting-like effect, coupling torsion (fibril twist) and extension. For freely-rotating boundary conditions, we identify...

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Bibliographic Details
Published in:Soft matter 2023-08, Vol.19 (33), p.6376-6386
Main Authors: Leighton, Matthew P, Kreplak, Laurent, Rutenberg, Andrew D
Format: Article
Language:English
Subjects:
Bifurcations
Boundary conditions
Collagen
Elastic anisotropy
Elastic properties
Elastomers
Fibrils
Parameterization
Rotation
Shape effects
Torsion
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Summary:We investigate the elastic properties of anisotropic elastomers with a double-twist director field, which is a model for collagen fibrils or blue phases. We observe a significant Poynting-like effect, coupling torsion (fibril twist) and extension. For freely-rotating boundary conditions, we identify a structural bistability at very small extensional strains which undergoes a saddle-node bifurcation at a critical strain - at approximately 1% strain for a parameterization appropriate for collagen fibrils. With clamped boundary conditions appropriate for many experimental setups, the bifurcation is not present. We expect significant helical shape effects when fixed torsion does not equal the equilibrium torsion of freely-rotating boundary conditions, due to residual torques. We study the mechanical properties of double-twist elastomers, a model for collagen fibrils. We find that fibril extension is coupled to torsion, leading to a structural bistability and bifurcation.
ISSN:1744-683X
1744-6848
DOI:10.1039/d3sm00554b