Effect of seawater immersion on the drill induced delamination failure in glass fiber reinforced polymer composites – Experimental and statistical analysis

•Marine glass fiber reinforced composites are drilled.•The effects of seawater treatment on the increase in drill-induced delamination failure are investigated.•Different material thicknesses (6, 8, and 10 mm) and immersion times (20, 40, and 60 days) were examined.•The significance of spindle speed as an input deciding parameter is emphasized.•The increase in peel up delamination failure seen after 60 days of seawater immersion was 290.22, 305.86 and 250.81 %.•The increase in the push down delamination failure seen after 60 days of seawater immersion was 69.48, 76.38 and 64.28 % in 6, 8 and 10 mm composites.