Multiscale stress deconcentration amplifies fatigue resistance of rubber

Jason Steck; Junsoo Kim; Yakov Kutsovsky; Zhigang Suo

doi:10.1038/s41586-023-06782-2

Multiscale stress deconcentration amplifies fatigue resistance of rubber

Nature. 2023 Dec;624(7991):303-308. doi: 10.1038/s41586-023-06782-2. Epub 2023 Dec 13.

Authors

Jason Steck^#¹, Junsoo Kim^#^{1

2}, Yakov Kutsovsky³, Zhigang Suo⁴

Affiliations

¹ John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, MA, USA.
² Department of Mechanical Engineering, Northwestern University, Evanston, IL, USA.
³ Office of Technology Development, Harvard University, Cambridge, MA, USA. yakov@materiax.ai.
⁴ John A. Paulson School of Engineering and Applied Science, Harvard University, Cambridge, MA, USA. suo@seas.harvard.edu.

^# Contributed equally.

PMID: 38092910
DOI: 10.1038/s41586-023-06782-2

Abstract

Rubbers reinforced with rigid particles are used in high-volume applications, including tyres, dampers, belts and hoses¹. Many applications require high modulus to resist excessive deformation and high fatigue threshold to resist crack growth under cyclic load. The particles are known to greatly increase modulus but not fatigue threshold. For example, adding carbon particles to natural rubber increases its modulus by one to two orders of magnitude^1-3, but its fatigue threshold, reinforced or not, has remained approximately 100 J m^-2 for decades^4-7. Here we amplify the fatigue threshold of particle-reinforced rubbers by multiscale stress deconcentration. We synthesize a rubber in which highly entangled long polymers strongly adhere with rigid particles. At a crack tip, stress deconcentrates across two length scales: first through polymers and then through particles. This rubber achieves a fatigue threshold of approximately 1,000 J m^-2. Mounts and grippers made of this rubber bear high loads and resist crack growth over repeated operation. Multiscale stress deconcentration expands the space of materials properties, opening doors to curtailing polymer pollution and building high-performance soft machines.