Materials such as glacial ice can deform viscously over long timescales while also experiencing brittle fracture. We seek to answer how a viscous flow connects to classical elastic fracture mechanics by constructing the disturbance fields using a viscoelastic correspondence principle and asymptotic methods to identify their underlying structure. We focus on two different viscoelastic rheologies: the Kelvin-Voigt solid, which introduces viscosity to an elastic material, and the linear Maxwell fluid, which exhibits viscous flow over long time scales.

For a Kelvin-Voigt solid, we explore the effects of confinement on a propagating crack in a strip geometry. We identify a two-deck asymptotic structure in the limits where the strip width is large or small compared to the characteristic viscoelastic length scale, revealing different balances in elastic and viscous stresses.

For the Maxwell fluid, we recover viscous behaviour far from the crack and a classical mode-I elastic fracture field near the crack tip. We identify a universal viscoelastic region that connects these limits, providing a relationship between the stress intensity factors of the outer viscous and inner elastic solutions.