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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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Fiber‐Reinforced Viscoelastomers Show Extraordinary Crack Resistance That Exceeds Metals
Abstract Soft fiber‐reinforced polymers (FRPs), consisting of rubbery matrices and rigid fabrics, are widely utilized in industry because they possess high specific strength in tension while allowing flexural deformation under bending or twisting. Nevertheless, existing soft FRPs are relatively weak against crack propagation due to interfacial delamination, which substantially increases their risk of failure during use. In this work, a class of soft FRPs that possess high specific strength while simultaneously showing extraordinary crack resistance are developed. The strategy is to synthesize tough viscoelastic matrices from acrylate monomers in the presence of woven fabrics, which generates soft composites with a strong interface and interlocking structure. Such composites exhibit fracture energy,Γ, of up to 2500 kJ m−2, exceeding the toughest existing materials. Experimental elucidation shows that the fracture energy obeys a simple relation,Γ = W · lT, whereWis the volume‐weighted average of work of extension at fracture of the two components andlTis the force transfer length that scales with the square root of fiber/matrix modulus ratio. SuperiorΓis achieved through a combination of extraordinarily largelT(10–100 mm), resulting from the extremely high fiber/matrix modulus ratios (104–105), and the maximized energy dissipation density,W. The elucidated quantitative relationship provides guidance toward the design of extremely tough soft composites.
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- Award ID(s):
- 1903308
- PAR ID:
- 10455341
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 32
- Issue:
- 31
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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