Delamination damage typically occurs at composite hole-exit as a result of Mode-I interlaminar opening fracture . The typical binary images of delamination damage in drilling of two composites are shown in Fig. and can be quantified by the delamination damage factor Fda . The regression function 𝑓𝑓 𝐷𝐷 of Fda can be calculated following Eq. ( ) and the values of coefficients are shown in Table . The R-Squared (R 2 ) values are higher than 0.85 which indicates a satisfactory performance of the proposed regression models . The prediction accuracy of the models will be further verified by experimental results.