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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Tough, aorta-inspired soft composites
Spatial variations in fiber alignment (and, therefore, in mechanical anisotropy) play a central role in the excellent toughness and fatigue characteristics of many biological materials. In this work, we examine the effect of fiber alignment in soft composites, including both “in-plane” and “out-of-plane” fiber arrangements. We take inspiration from the spatial variations of fiber alignment found in the aorta to three-dimensionally (3D) print soft, tough silicone composites with an excellent combination of stiffness, toughness, and fatigue threshold, regardless of the direction of loading. These aorta-inspired composites exhibit mechanical properties comparable to skin, with excellent combinations of stiffness and toughness not previously observed in synthetic soft materials.
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- Award ID(s):
- 1720530
- NSF-PAR ID:
- 10414971
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 119
- Issue:
- 28
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2123497119
