Applications of the Incremental Hole-Drilling Method for Measurement of Non-Uniform Residual Stresses in Fiber Metal Laminates.

In this paper, the incremental hole-drilling method is used to measure experimentally with accuracy non-uniform residual stresses in each ply of fiber metal laminate (FML) composites. Integral method was used for the approximation of residual stress. This method is considered a constant and uniform residual stress analysis at each hole-drilling depth increment. First, finite element method is used to calculate the calibration coefficients matrix of the incremental hole drilling process. The calibration coefficients matrix determined by finite element analysis can be used directly in the experiment. Calibration coefficients matrix is used to relate the measured strain relaxation field with the existing residual stresses prior to the hole-drilling process. Also, for the experimental determination, released strains induced by high speed drilling process on FML composites with a stacking sequence of [AL/0₂ ° /90₂ °]_S have been quantified. Finally, the experimental measurements are compared with the theoretical predictions of the classical laminate theory. Good agreement between the experimental data and theoretical prediction show that, incremental hole-drilling technique can be proved to be successfully applied for measuring non-uniform residual stresses in FML composites. [ABSTRACT FROM AUTHOR]