Improvement and validation of residual stress measurement in composite laminates using the incremental hole-drilling method

Abstract In this paper, the incremental hole-drilling (IHD) method has been improved by attaching strain gauge rosettes on both top and bottom surfaces, and changing the calculation algorithm for solving the ill-conditioned problem. In order to assess the feasibility and accuracy of the improved IHD method, an experiment of measuring the in-plane stress distribution in a composite laminate under bending was proposed. The composite laminate, which is bended by an external pure bending moment and fixed in a stable state, contains an in-plane stress distribution with obvious gradients in thickness direction, which is essentially similar to residual stresses. A plain woven T800H/803 specimen was tested in the proposed experiment with the improved IHD method. The results calculated using both top-surface and bottom-surface measured strains, and by iteration algorithm, showed good agreement with the finite element method (FEM) simulation and high calculation efficiency.