Influence of artificial notch length in composite material on damage indicator values

Novel experimental method, which provides visualization of interference fringe patterns caused by inserting of artificial notch of prefixed length in composite material, is developed. Deformation response to local material removing is measured by electronic speckle-pattern interferometry. Interferogram interpretation in terms of in-plane displacement components produces determination of two deformation parameters. These parameters represent current damage indicators, which are essential for quantitative description of damage accumulation inherent in fatigue loading of specimens with stress concentrators. Both damage indicators are derived on a base of direct physical measurements by fringe order counting. Analysis of uncertainties in damage indicators determination, which are connected with incorrect prescribing of artificial notch length, is presented.