The role of patch-parent configurations on the tensile response of patch repaired carbon/epoxy laminates

This work investigated the individual and associated effects of parent laminate and patch orientations with stacking sequence on the tensile response of adhesively bonded external patch repaired carbon/epoxy laminates. Four kinds of parent laminates ([0]₄, [45]₄, [0/45]_s, [45/0]_s) were repaired with double sided external patches of four different configurations ([0]₂, [45]₂, [45/0], [0/45]), having two laminae on each side. Real time Digital Image Correlation (DIC) was employed to capture the two dimensional strain field, damage onset and damage growth of the repaired specimens during the tests. The results reveal that the angle of orientation of plies of both the patch and the parent laminate is a key design parameter which affects the performance after the repair. The results reveal that the repair of main load bearing plies (0°) of parent laminate with [45]₂ patches presented the most favourable residual tensile behaviour by effectively releasing the stress concentration in the damaged area. The maximum residual strength after repair with [45]₂ patch for [0]₄, [45]₄, [0/45]_s, [45/0]_s laminates was approximately 70%, 115%, 90% and 80% respectively.