Crack-tip stress in gels

Calculations of drying stresses have previously been presented in terms of the total stress, which is the sum of the stresses in the liquid and solid phases. However, the criterion for fracture involves the stress on the solid phase. In this note, the stress on the network at the crack tip is given explicitly. It is shown that the stress at the tip of a flaw can be tensile, even though the solid network is in compression elsewhere.