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 (sigma(c) =37.3 MPa, sigma(offset) =6.0 MPa and sigma(c) =20.1 MPa, sigma(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.

Automated summary

Commercial copy paper behaves like Al foils in terms of orthotropic constitutive behavior, with mode I crack tips developing quasistatic, fully plastic, steady-state conditions, including a positive offset stress due to fiber bridging. Reversed plastic zones dependent on orientation were observed in the crack wake, while transverse necking fracture processes were absent.