Large Strain and Fracture of Multiple Network Elastomers

Abstract : We investigated systematically the mechanical and fracture properties of multiple network elastomers synthesized by successive swelling/polymerization steps inspired by the molecular architecture of Gong’s double network gels. A more versatile synthesis method was used to vary continuously the isotropic degree of prestretching λ0 of the first network resulting in a wider range of mechanical behaviours, where λ0 controls the Young’s modulus at small strain and the strain hardening at large strain. If the first network is diluted enough (<10%) molecular bond breakage occurs in this prestretched network at high strain while avoiding sample failure. The degree of dilution controls the amount of damage and therefore the slope of the stress-strain curve. Finally, for the most diluted systems (<3%), a yield stress and a necking phenomenon was observed. Changing the degree of crosslinking of the first network or the monomers used led to the same qualitative mechanical behaviour. The fracture energy Γ was shown to be an increasing function of λ0 however different regimes could be distinguished with macroscopic fracture occurring before or after bulk damage was detected. Visualisation techniques such as Digital Image Correlation and embedded mechanoluminescent molecules were used to map a damage zone in front of the crack tip, the size of which increased with λ0. Finally, the toughening mechanism of the multiple network elastomers could be understood in a nearly quantitative way within the framework of Brown's model of fracture of double network gels.
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Submitted on : Friday, May 24, 2019 - 1:01:16 AM
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  • HAL Id : tel-02138641, version 1

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Pierre Michel Millereau. Large Strain and Fracture of Multiple Network Elastomers. Chemical Physics [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2017. English. ⟨NNT : 2017PA066082⟩. ⟨tel-02138641⟩

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