Necking of double-network gels: Constitutive modeling with microstructural insight

Area of Science:

• Polymer Science
• Materials Science
• Mechanics of Materials

Background:

• Double network (DN) gels exhibit complex mechanical behavior under large deformations.
• Previous models focused on the first network's role in pre-necking inelasticity.
• The role of the second network during necking and post-necking stages requires further elucidation.

Purpose of the Study:

• To propose a constitutive model for DN gels that describes necking behavior.
• To elucidate the role of the second network in the necking and post-necking stages.
• To challenge the assumption of a purely elastic second network in DN gel modeling.

Main Methods:

• Development of a constitutive model based on statistical micromechanics of interpenetrating polymer networks.
• Division of DN gel response into prenecking, necking, and postnecking zones.
• Incorporation of three competing mechanisms governing network rearrangement during necking.

Main Results:

• The second network's chains contribute to energy dissipation by connecting fragments of the first network.
• The model accurately predicts DN gel behavior across all three deformation stages.
• Finite-element implementation visualizes necking instability initiation and propagation.

Conclusions:

• The proposed model provides a comprehensive description of DN gel necking behavior.
• The second network plays a crucial role in energy dissipation and material stability.
• This work advances the understanding and modeling of soft materials with complex architectures.