Fatigue-Resistant elastomers

Abstract The resistance of a material to the growth of a crack is characterized by fracture toughness under monotonic load, and by fatigue threshold under cyclic load. The fatigue threshold of engineering elastomers is commonly limited to ∼50 J/m2, much below their toughness (103∼105 J/m2). Here we report fatigue-resistant elastomers with threshold beyond 500 J/m2. Such an elastomer is a composite of two elastomers: a lattice of a hard elastomer embedded in a matrix of soft elastomer. Both the hard and soft elastomers are elastically stretchable, with small hysteresis. At a crack front in the composite, the soft matrix shears greatly, which de-concentrates stress in the hard lattice. When the crack advances in the composite, the energy dissipated scales with the feature size of the lattice. By contrast, when a crack advances in a homogeneous elastomer, the energy dissipated scales with the mesh size of the polymer network. The fatigue-resistant elastomers open new opportunities for applications requiring stretchable materials.