Nonlinear displacement field in the vicinity of notch-tip in rubber toughened PMMA

Displacement field in the vicinity of notch-tip in a rubber toughened PMMA was measured at different levels of load using moiré interferometry. The displacement field obtained was then compared with the analytical fields calculated on the basis of the linear elastic fracture mechanics and obtained from nonlinear finite element analysis that was based on the deformation theory of plasticity. The displacement field experimentally measured at about 90% of the maximum load exhibited nonlinearity. There were both similarity and difference between the measured and the analytical displacement fields. The nonlinearity of the displacement field is also discussed on the basis of the microscopic damage formation in the notch-tip region.