Steady-state crack growth in heterogeneous fiber network thin sheets.

Commercial copy paper is a thin sheet material that has orthotropic constitutive behavior reminiscent of Al foils. Similar to Al foils, mode I crack tips in paper developed quasistatic, fully plastic, steady-state conditions even though plastic deformation in paper is not isochoric. The characteristic steady-state stress for crack growth depended on specimen orientation and contained a positive offset stress due to fiber bridging ( σ c = 37.3 MPa, σ offset = 6.0 MPa and σ c = 20.1 MPa, σ offset = 2.9 MPa for the machine and cross direction orientations, respectively). Orientation-dependent, reversed plastic zones were observed in the crack wake and transverse necking fracture processes were not present. • Steady-state, mode I crack growth was observed in single-edge notched specimens. • Steady-state process zone sizes were directly measured from full-field strain maps. • The crack growth was controlled by a characteristic steady-state stress. • The characteristic steady-state stress was offset because of fiber bridging. [ABSTRACT FROM AUTHOR]