Experimental Analysis of the Influence of Drill Point Angle and Wear on the Drilling of Woven CFRPs

Abstract

This paper focuses on the effect of the drill geometry on the drilling of woven Carbon Fiber Reinforced Polymer composite (CFRPs). Although different geometrical effects can be considered in drilling CFRPs, the present work focuses on the influence of point angle and wear because they are the important factors influencing hole quality and machining forces. Surface quality was evaluated in terms of delamination and superficial defects. Three different point angles were tested representative of the geometries commonly used in the industry. Two wear modes were considered, being representative of the wear patterns commonly observed when drilling CFRPs: flank wear and honed cutting edge. It was found that the crossed influence of the point angle and wear were significant to the thrust force. Delamination at the hole entry and exit showed opposite trends with the change of geometry. Also, cutting parameters were checked showing the feed’s dominant influence on surface damage.

Drilling optimization of woven CFRP laminates under different tool wear conditions: a multi-objective design of experiments approach

“…Peel-up decreases with choosing medium point angles (90°-116°) and low cutting speeds (25 m/min). The opposite effect was found for push-out where higher point angles (107°-113°) and higher cutting speeds (69 m/min-98 m/min) would improve the results; this observation is also in alignment with the earlier reports (Heisel and Pfeifroth 2012;Feito et al 2014b) and suggest that depending on the wear type and/or a particular design objective, the cutting parameters can be changed to maximize the process quality. However, this may be viewed as a complex paradigm for practical applications, leading to the following multi-objective/overall optimization results.…”

“…The raw experimental data for thrust force, in-and out-delaminations under tested drilling configurations were previously published in the study (Feito et al 2014b). This work is directly focused on statistical evaluation of main and interaction factor effects as well as the multi-objective optimization process under different tool wear levels.…”

“…It is interesting that for the worn tools, this factor contribution increases by~25 % for the flank wear tool and~65 % for the honed edge tool, compared to the new tool. This suggests that as the drill bit is worn, the same feed rate can cause less entry delamination in the CFRP laminate (or in a different way, to avoid excessive delamination, the feed rate should be low for new tools); see also (Feito et al 2014b). Regarding the rest of parameters, the new and flank wear tools have almost the same sensitivity to the point angle (29.02 vs. 21.91 %) followed by the cutting speed (15.42 vs. 17.62 %).…”

“…3 Fig. 7 Overall variation of the CFRP drilling quality with the drill point angle, cutting speed and feed rate, under different wear conditions (trends have been plotted based on test data in (Feito et al 2014b)) …”

The Effect of Drilling Parameters on Strength of Glass Fibre-Epoxy Laminates by Produced Hand Lay-Up

“…The delamination was occurred at the entrance and exit of the hole [14]. This factor (Fd) is defined as the ratio to nominal diameter of the hole of maximum diameter in the delaminated area ( Figure 2) [15]. The delamination factor (Fd) around the hole can be determined as empirical.…”