Investigation of Important Parameters in Residual Stress Determination in Isotropic Plates and Laminated Composites by Slitting Method

In the slitting method, a small width slit is created incrementally through the thickness of the stressed specimen and the released strains in each increment are recorded by a strain gauge. Compliance coefficients relate the measured strains to the residual stresses. This paper investigates the important parameters influencing the calculation of compliance coefficients for isotropic plates and laminated composites by finite element analysis. First, the process of slitting in isotropic materials is simulated using two and three-dimensional finite element models. The results show complete agreement between these two models. Calculation of average strain at the strain gauge location is necessary for the calculation of compliance coefficients. For this purpose, strain-based and displacement-based methods are used. In addition, the effect of slit width on compliance coefficients is checked. Then, released strains by strain gauges with different gauge-lengths are compared with each other. The results show that the strain gauges with smaller gauge-lengths can record higher values of released strain and consequently increase the precision of measurements. Lastly, compliance coefficients for two glass/epoxy and carbon/epoxy laminates are calculated using the proposed three-dimensional model.