Elastic displacements along the flanks of internal cracks in rubber

Biaxial tensile experiments with thin rubber sheets, containing an internal crack, reveal the possibility to simulate and readily check the exact linear-elastic crack-flank displacements. The resulting deformed shape and the final position during loading of an internal inclined crack in an infinite, biaxially loaded elastic plate, was defined by measuring the crack-flank displacements, and the deformation features of the internal crack in rubber sheets. The results were compared with the linear-elastic displacements and the respective features, which have been obtained from an infinitesimal elasticity theory.The calculation of these displacement and deformation properties for a given crack presupposes the determination of two parameters, which characterize the loading conditions of the boundaries of the elastic cracked plate. These parameters have been determined as Lagrangian or Eulerian ones from the homogeneous strains at the boundaries of the elastic sheet, assuming either a Hookean, or a neo-Hookean or a Mooney material behavior for the elastic sheet.It has been shown that, except for the vicinities of the crack tips and for the regions of the imposed boundary strains in the experiments, the observed crack-flank displacements agree satisfactorily with the respective displacements obtained from the infinitesimal theory, if the material behavior is assumed as a neo-Hookean one, and the boundary-loading parameters are calculated as Eulerian ones.