부산대학교 도서관

Drilling is an inevitable process for component assembly which need appropriate control aiming damage reduction. To study such drill-induced damages, Glass and Natural fiber composites with unidirectional (11) and cross-ply lay-up (12) were drilled using Twist and Annular Core drill tool of varying diameters (6 and 8 mm). The derivative of modal analysis (natural frequency, damping) and delamination are the factors considered for the analysis. In the chosen laminates, maximum variation in the natural frequency was observed to be 8.98% in N12 and 8.60% in G12 for twist drill of 8 mm, whereas the core drill of 8 mm contributes to 0.51% and 0.54%. A similar trend was observed in damping factor showing a maximum variation of 26.98% (N12) and 11.30% (N12) with 8 mm twist and core drill, respectively. Similarly, the maximum delamination factor was observed to be 1 .62 and 1.30 with 8 mm core drill in G12 and N12 which is lower than the 6 and 8 mm twist drills. Further, twist drilling experiences both peel-up and push down delamination in N12, N11 which was eliminated by the core drill. Thus, core drill exhibits distinct advantages with reduced damage and retained structural properties.