Quality assessment and delamination force evaluation in drilling glass fibre-reinforced plastic laminates - a finite element analysis and linear elastic fracture mechanics approach

Drilling experiments were conducted on bidirectional glass fibre- reinforced plastic (GFRP) composite laminates using high-speed steel drill tools in order to verify the effect of machining parameters and fibre concentration on the surface finish, hole quality and delamination. The experimental results revealed that the surface roughness (SR) value and hole diameter variation can be correlated with the drill speed, feed rates and fibre content. A finite element analysis (FEA) model is used to predict the effect of fibre percentage on the thrust force causing delamination. A modified simple plate bending equation derived from linear elastic fracture mechanics (LEFM) is used to validate the FEA results. The predicted FEA results are shown to agree reasonably well with LEFM model results.