Polyurethane (PU) elastomers are among the most used rubberlike materials due to their combined
merits, including high abrasion resistance, excellent mechanical properties, biocompatibility, and good
processing performance. A PU elastomer exhibits pronounced hysteresis, leading to a high toughness on
the order of 104 J/m2. However, toughness gained from hysteresis is ineffective to resist crack growth
under cyclic load, causing a fatigue threshold below 100 J/m2. Here we report a fatigue-resistant PU
fiber–matrix composite, using commercially available Spandex as the fibers and PU elastomer as the
matrix. The Spandex fibers are stiff, strong, and stretchable. The matrix is soft, tough, and stretchable.
We describe a pullout test to measure the adhesion toughness between the fiber and matrix. The test
is highly reproducible, showing an adhesion toughness of 3170 J/m2. The composite shows a maximum
stretchability of 6.0, a toughness of 16.7 kJ/m2, and a fatigue threshold of 3900 J/m2. When a composite
with a precut crack is stretched, the soft matrix causes the crack tip to blunt greatly, which distributes
high stress over a long segment of the Spandex fiber ahead the crack tip. This deconcentration of stress
makes the composite resist the growth of cracks under monotonic and cyclic loads. The PU elastomer
composites open doors for realistic applications of fatigue-resistant elastomers
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This content will become publicly available on December 14, 2024
Multiscale stress deconcentration amplifies fatigue resistance of rubber
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 magnitude1,2,3, but its fatigue threshold, reinforced or not, has remained approximately 100 J m−2 for decades4,5,6,7. 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.
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- Award ID(s):
- 2011754
- NSF-PAR ID:
- 10500452
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Nature
- Volume:
- 624
- Issue:
- 7991
- ISSN:
- 0028-0836
- Page Range / eLocation ID:
- 303 to 308
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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