Session: 13-15-01: Mechanics of Soft Materials I

Paper Number: 173150

Supersonic Crack Propagation in Polymer-Like Networks 

Polymers, as a subset of soft materials, are well known to exhibit highly nonlinear mechanical behavior, often characterized by large deformations and strain-stiffening responses. These phenomena are effectively captured by hyperelastic constitutive models, which offer a robust framework for describing the complex stress-strain relationships inherent to such materials. However, in the context of fracture, these nonlinearities give rise to unconventional fracture dynamics that diverge significantly from the assumptions of classical linear elastic fracture mechanics (LEFM). In particular, crack propagation speeds in soft polymers deviate significantly from classical predictions, including instances of supersonic fracture that appear to defy traditional thermodynamic constraints. These observations challenge established theories and motivate a re-examination of the mechanics governing fracture in nonlinear soft materials.

In this work, we present a computational study of dynamic fracture in polymer-like networks, defined here as stretchable lattices composed of nonlinear strands with mechanical responses analogous to those of entropic polymer chains. These strands are modeled to capture essential features such as pronounced strain-dependent stiffness and large-deformation behavior. The resulting network serves as a simplified yet representative platform for studying the fracture behavior of a broad range of soft materials, including elastomers and stretchable metamaterials. Within this framework, we observe crack propagation speeds that eclipse the Rayleigh wave speed and are strongly influenced by both material and geometric nonlinearities.

Based on these findings, we propose a scaling law that links crack speed to key material and structural parameters, including strand stiffness and lattice topology. This provides not only insight into the mechanisms driving supersonic fracture but also a predictive framework for understanding and controlling fracture dynamics in polymer-like networks.

To perform the numerical analysis, we developed a mathematical model for the dynamic response of hyperelastic strands and implemented a dynamic fracture simulation tailored to the discrete lattice architecture—accounting for inertia, nonlinear force-extension relationships, and rupture criteria based on critical stretch. To validate our computational findings, we fabricated physical prototypes of the lattice structures using a stretchable architected material with polymer-like behavior and conducted dynamic fracture experiments under high-speed imaging. The experimental observations show good qualitative agreement with the numerical predictions, supporting the predictive capability of the model.

Overall, this study contributes to a deeper understanding of the mechanisms behind supersonic crack propagation in polymers and polymer-like networks, and establishes a foundation for the design of stretchable architected materials with tailored fracture responses—advancing the broader field of fracture mechanics in soft materials.

Presenting Author: Victor Riera Naranjo Georgia Institute of Technology

Presenting Author Biography: PhD student in Aerospace Engineering at Georgia Tech under Prof. Bolei Deng. Research focuses on computational study of metamaterials and nonlinear mechanics.

Authors:

Victor Riera Naranjo Georgia Institute of Technology
Chase Hartquist University of Florida
Leonid Sopizhenko Georgia Institute of Technology
Saahil Gaonkar Georgia Institute of Technology
Bolei Deng Georgia Institute of Technology