Residual stress measurement of fiber metal laminates using incremental hole-drilling technique in consideration of the integral method

• The non-uniform residual stresses of FML using integral method have been determined.
• Calibration factors of developed integral method using FEM have been calculated.
• Experimental results were compared with the theoretical predictions from CLPT.
• The residual stresses in the thickness of FML are non-uniform and remarkable.
• For each metal and lamina ply of FML a matrix of calibration coefficient is needed.

In this manuscript, integral method was used for the approximation of residual stresses field in fiber-metal laminates (FMLs). Initially, calibration coefficients matrix for the integral method were determined numerically by the finite element program using ANSYS software. The calibration coefficients were used to relate the measured strains relaxation field with the existing residual stresses prior to the IHD process. Subsequently, FML specimens with symmetric stacking sequence of [AL/02°/902°]S were manufactured. Next, the IHD experiment by high speed drilling machine were performed and released strains caused by the change in hole-geometry have been obtained. Finally, experimental results from IHD experiment were compared with the theoretical predictions from classical lamination theory. Very good agreements with the experimental and theoretical results show that, the IHD technique can be successfully applied for measuring residual stresses in FML composites.