Effect of interactions of two holes on tensile behavior of patch repaired carbon/epoxy woven laminates

Abstract

The conventional case of patch repair involves bonding a patch over single damage/hole in the laminate. This work investigates the effect of interaction of two holes on the tensile behavior patch repaired carbon epoxy woven laminates. The specimens of [0°/45°/45°/0°] laminates were repaired with adhesively bonded two-ply [45°]2 external patches. Three different cases of drilled specimens were produced with different hole arrangements viz. specimens with single central hole (SH), with two holes aligned along the longitudinal axis (LH) and with two holes along transverse axis (TH). The two-hole specimens were repaired with two different types, i.e. single large patches (SP) and with the two smaller patches (DP) of combined bonding area equal to the single large patches. Digital image correlation (DIC) was employed to capture strain contours. The results reveal the difference in the load transfer through the patches depending upon the arrangement of holes. The TH repaired specimen exhibit significant load recovery (SP-32.75%, DP-34.62%) while the LH specimens result in very marginal (SP- 6.11%, DP-4.10%) recovery compared to their drilled case. The TH specimen failed by crack growing through both the holes beneath the patch, while the LH specimens failed by the failure through only one hole. The use of single large patch over multiple holes and multiple small patches individually over each hole has no significant influence on load recovery.