Damage reduction in the drilling of carbon fibre composites
Aniruddha Gupta (Aniruddha.Gupta@Warwick.ac.uk), Supervisor: Dr. Stuart Barnes
1. Introduction- drilling of CFRP
 Mechanical drilling is one of the final processes in many
industries particularly in Aircraft and Aerospace industries for
riveted and bolted joints
 Drilling of CFRPs has been difficult due to the shorter tool life
and damages like delamination and chip out
 According to a study, 60% of all the part rejections in air craft
industry is associated to delamination in the drilling
 Inhomogeneous and anisotropic nature of CFRP differs it from
metal drilling e.g. different matrix and fibre properties and
mechanism of chip removal
3. Approach to solve the problem – Ultrasonic
assisted drilling
5. Methodology and design of experiments
Any single process is not sufficient
Optimize tool Geometry
(shear inserts, diamond
coatings)
Conventional
drilling
Taguchi orthogonal
Ultrasonic
assisted
drilling
arrays, Response surface
X-Ray micro CT scanning
methodology for
and image processing for
Improved
experiments
damage identification
Hole
Ultrasonic
vibrations
Quality
Optimise UAD parameters
Use of Cutting Fluid
(Vibration frequency,
2. Problems in the current available processes
 Conventional drilling
(Conventional, liq.N2,
amplitude, cutting speed
UAD has shown improvement in surface
finish and lesser thrust force in metal machining
CO2 coolants)
and feed rate
6. Studies performed
 Comparison of the conventional drilling and the ultrasonic assisted drilling
 Laser
Matrix burns
At high melting
point of carbon
fibres
0.05, 67.2
65
0.02, 64.63
60
0.02, 60.87
75
0.08, 76.62
0.05, 71.55
70
65
0.02, 62.335
60
0.02, 58.555
55
55
0.01
0.03
0.05
0.07
0.09
0.01
0.03
Feed Rate (mm/rev)
With Ultrasonic
100, 70.96
80, 71.04
100, 67.31
80, 67.26
70
80
90
100
110
Cutting speed (m/min)
With Ultrasonic
120, 66.77
Without Ultrasonic
0.07
0.09
0.08, 80.62
0.02, 58.065
0.01
0.03
Without Ultrasonic
130
0.05, 71.59
0.02, 63.77
0.02
0.08, 75.12
0.05, 67.06
0.04
0.06
Feed rate (mm/rev)
With Ultrasonic
0.08
0.07
0.09
Without Ultrasonic
Average effect of vibration
amplitude
0.02, 59.16
0
0.05
Feed Rate (mm/rev)
With Ultrasonic
0.08, 78.93
80
75
70
65
60
55
50
0.08, 75.02
0.05, 71.895
0.05, 67.225
0.02, 64.35
Average effect of feed rate
120, 72.29
120
0.05
Feed Rate (mm/rev)
With Ultrasonic
Without ultrasonic
Average effect of cutting speed
80
75
70
65
60
55
50
0.05, 66.76
Thrust Force (N)
70
Thrust Force (N)
0.05, 71.32
85
80
75
70
65
60
55
0.1
Thrust force (N)
Exit
0.08, 77.18
0.08, 73.71
75
Cutting speed = 120 m/min
0.08, 78.98
80
Thrust force (N)
Entrance
 Develop a thorough understanding of ultrasonic assisted drilling
for carbon fibre composite material
 Minimize the damages in the drilling of carbon fibre composite
material through ultrasonic assisted drilling
 Process parameters –
• Cutting speed
• Feed rate
• Vibration amplitude
• Vibration frequency
• Tool geometry
• Cutting fluid (Conventional & cryogenic coolants)
Thrust Force (N)
entrance and exit
& some internal
damages
4. Problem definition
Cutting speed = 100 m/min
Cutting speed = 80 m/min
Thrust force (N)
Delamination at
80
75
70
65
60
55
50
60, 71.43
20, 71.84
0
20
Without Ultrasonic
100, 71.03
40
60
80
Amplitude (%)
100
120
o Ultrasonic assistance helps in reducing the thrust force at all cutting speeds.
o Higher the amplitude, lower the thrust force at higher cutting speeds.
o Feed rate is the most effective parameter for thrust force.
 AWJM
Irregular dimensions,
kerf width and washed
out matrix
References
o Liu, D.F., Y.J. Tang, and W.L. Cong, A review of mechanical drilling for composite laminates.
Composite Structures, 2012. 94(4): p. 1265-1279
o Liao, Y.S., Y.C. Chen, and H.M. Lin, Feasibility study of the ultrasonic vibration assisted drilling of
Inconel superalloy. International Journal of Machine Tools & Manufacture, 2007. 47(12-13): p.
1988-1996.
o Makhdum, F., et al., Cutting forces in ultrasonically assisted drilling of carbon fibre-reinforced
plastics. Modern Practice in Stress and Vibration Analysis 2012 (Mpsva 2012), 2012. 382
o Farrukh Makhdum et al., Ultrasonically Assisted Drilling of Carbon Fibre Reinforced Plastics,
2012, Solid State Phenomena, 188, 170
 USM
NO DELAMINATION
But very slow process
maximum MRR = 12 𝑚𝑚3 /𝑠
Collaborators
Material :
Machine :
7. Further studies planned
 Variation of the ultrasonic parameters to minimize the damage
 Variation in the tool geometry with the optimized parameters to minimize the
damages further and propose a new tool design
 Use of cryogenic coolant like CO2 and liq. N2 to minimize the damages further
Drills :