International audienceIn this paper, experimental analysis has been done to study delamination phenomenon when drilling 4 shaft satin weave carbon fiber and epoxy matrix using twist drill. The composite is exposed to generate damage during processing due to delamination phenomenon. It was found that the increase of the feed rate was related to the apparition of superficial defects. Indeed, this increase gave birth to new types of drilling defects

Bouami, Souhail,

Bouaziz, Zoubeir

Habak, Malek

Mahdi, Amani

Turki, Yosra

English

Archive Ouverte en Sciences de l'Information et de la Communication

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Experimental analysis of the defects of drilling woven
CFRP
Amani Mahdi, Yosra Turki, Zoubeir Bouaziz, Malek Habak, Souhail Bouami
To cite this version:
Amani Mahdi, Yosra Turki, Zoubeir Bouaziz, Malek Habak, Souhail Bouami. Experimental analysis
of the defects of drilling woven CFRP. International Conference on Mechanics and Energy ICME’2018,
Dec 2018, Hammamet, Tunisia. ￿hal-02168949￿
International Conference on Mechanics and Energy 
December 20-22, 2018, Hammamet, TUNISIA                                                            ICME'2018 
 
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Experimental analysis of the defects of drilling woven CFRP 
Amani Mahdi1*, Yosra Turki1, Zoubeir Bouaziz1, Malek Habak2, Souhail El Bouami2 
1 Laboratory of Applied Fluid Mechanics, Environment and Process Engineering, National School of Engineers of Sfax, Route Soukra 
Km 3.5, 3035 Sfax, Tunisia 
2 Laboratory of Innovative Technology, IUT of Amiens, GMP Department, University of Picardie Jules Verne, Avenue des Facultés Le 
Bailly, 80001 Amiens Cedex 1, France 
 
 Abstract: In this paper, experimental analysis has been done to study delamination phenomenon when drilling 4 shaft satin weave 
carbon fiber and epoxy matrix using twist drill. The composite is exposed to generate damage during processing due to delamination 
phenomenon. It was found that the increase of the feed rate was related to the apparition of superficial defects. Indeed, this increase 
gave birth to new types of drilling defects.  
 
Keywords: drilling, delamination, woven CFRP. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Graphical abstract 
 
                                                          
*Corresponding author: Amani Mahdi 
E-mail: amani.mahdi@enis.tn. 
International Conference on Mechanics and Energy 
December 20-22, 2018, Hammamet, TUNISIA                                                            ICME'2018 
 
2 
 
1. Introduction 
Nowadays, composite materials are more and more 
used in many fields especially in aeronautic and 
aerospace industry. It has specific proprieties such as 
low density, high mechanical characteristics, easy 
manufacture of composite parts and zero thermal 
expansion coefficient [1]. Woven carbon fiber 
reinforced polymer (CFRP) has been used in hot parts 
of structures such as engines and nacelles in aerospace 
industry due to its high thermal protection [2]. The 
study of delamination phenomenon generated by 
drilling CFRP has a big importance because those types 
of superficial defects reduce the life of composite 
components. Indeed, delamination has spread in 
aeronautical structures during their service life. They 
are submitted to fatigue phenomenon because of 
aerodynamic turbulent flow [3]. Several researchers 
have studied the delamination phenomenon of 
unidirectional CFRP analytically, numerically and 
experimentally. Qui et al. [4] have studied the impact 
of machining parameters and tool structure on 
delamination phenomenon. They have used a 
unidirectional CFRP whose plies were in the same 
direction. Two types of tool geometry were utilized: 
twist and spur drills. They have noted that the bigger 
feed rate was applied, the more defects were appeared. 
The same results were obtained in many other 
researches works such as Li et al. [5] and Turki et al. 
[6]. Delamination obtained by the drilling of woven 
CFRP has been the current theme of research. There are 
many types of woven CFRP. The most popular one is 
based on 4 shaft satin weave (AS-4) carbon fiber and 
epoxy matrix because it is commonly used in aerospace 
industry. Feito et al. [7] have studied the effect of tool 
geometry on drilling AS-4 woven CFRP using brad, 
reamer and stepped drills. They have noted that 
delamination phenomenon was related to the tool 
structure. Brad drill caused more drilling defects than 
the other geometries. From the mentioned study, it 
appears that the study of delamination of woven CFRP 
have been poorly developed. So, it is still a challenge 
understand this phenomenon. In this paper, we are 
interested on the study of the defects of drilling AS-4 
woven CFRP using twist drill. The delamination at the 
entrance and the exit of the hole is also evaluated.     
2. Experimental work 
2.1 Workpiece material and drill 
The material studied in this work and shown in the 
figure 1 is a AS-4 woven CFRP composite based on 4 
shaft satin weave carbon fiber and epoxy matrix and 
composed of 18 plies with the same orientation. It was 
manufactured by Hexcel composites and it was made 
in plate of 100 mm x 100 mm x 4.6 mm thick by Zodiac 
aerospace. Uncoated twist carbide drill was utilized in 
this study. It has two sides and it was shown in the 
figure 2. Its nominal diameter is equal to 6.3 mm. It has 
150° tip angle, 5° cutting angle, 11° draft angle and 30° 
helix angle. 
 
11  
 
Fig. 1 AS-4 woven CFRP 
 
 
Fig. 2 Twist carbide drill 
2.2 Machining Tests 
The drilling operation was performed on a numerical 
controlled Charlyrobot CPR0705 machine. The used 
drilling mode in this study was without support and 
lubrification. So, the use of vacuum cleaner is 
necessary. Concerning the cutting conditions, the 
cutting parameters were summarized in table 1. 
Mahdi et al./ ICME’2018, December 20-22, 2018 
 
3 
 
Macroscopic observations of the drilling holes were 
made with Leica binocular loupe. The position of the 
drilling hole related to the textile float may influence 
the delamination phenomenon. However, Feito et al. 
[8] have indicated that this influence does not have a 
remarkable effect.  
 
Table 1 Cutting parameters used in drilling tests 
f [mm/rev] N [rpm] 
0.05 2000 
0.2 3500 
0.35 5000 
 
3. Results and discussion 
The hole quality was evaluated in terms of visual 
observation of delamination phenomenon at the 
entrance and the exit of the hole. We have noted, using 
the naked eye, that the increase of the feed rate f 
increases drilling defects. However, the increase of 
spindle speed N does not have a remarkable effect. The 
best quality obtained of the hole corresponds at f = 0.05 
mm/rev. Figure 3 shows macroscopic observations of 
the delamination phenomenon in entrance holes at N = 
3500 rpm using a scale of 2 mm. The effect of N on 
delamination is presented in the figure 4 at f = 0.2 
mm/rev using a scale of 2 mm. The use of twist drill 
causes also damages. We can see uncut fibers, chipping 
which is a mark made by the drilling operation and 
spalling which is a delamination accompanied by 
tearing of a piece of ply. These drilling defects are 
similar to results obtained in the case of drilling 
unidirectional CFRP composite [9].  
 
(a) Entrance defects 
  
f = 0.05 mm/rev f = 0.2 mm/rev 
 
f = 0.35 mm/rev 
(b) Exit defects 
  
f = 0.05 mm/rev f = 0.2 mm/rev 
 
f = 0.35 mm/rev 
                   delamination 
                    spalling  
                   chipping                    
                   uncut fibers 
Fig. 3 Macroscopic observations of the delamination 
phenomenon at N = 3500 rpm 
 
  
N = 2000 rpm N = 3500 rpm 
Fig. 4 The effect of spindle speed N on delamination 
phenomenon 
6. Conclusions 
An experimental analysis of the defects of drilling 
woven CFRP has been developed in this paper. It has 
been noted that the feed rate f is the most responsible 
one of delamination phenomenon. Also, the increase of 
f has given birth to several types of drilling defects. In 
further works, it will be important to calculate the 
Mahdi et al./ ICME’2018, December 20-22, 2018 
 
4 
 
delamination factor and to compare delamination in 
CFRP and woven CFRP.  
Acknowledgments 
This work is partially supported by Laboratory of 
Applied Fluid Mechanics. The authors also gratefully 
acknowledge the helpful comments and suggestions of 
the reviewers, which have improved the presentation. 
References 
[1] Nagaraja, Mervin AH, Divokara S et al. (2013) Effect of 
process parameters on delamination, thrust force and 
torque in drilling of carbon fiber epoxy composite, 
Research journal of recent sciences, vol. 2 (8), 47-51. 
[2] Laurent G. (2008) Généralités sur les matériaux 
composites. Ecole d’ingénieurs. < cel-00470296v1 > 
[3] Maillet I. (2013) Delamination propagation in composite 
material under vibratory fatigue, Institut supérieur de 
l’aéronautique et de l’espace, Theses book. 
[4] Qui X, Li P Niu Q et al. (2018) Influence of machining 
parameters and tool structure on cutting force and hole 
wall damage in drilling CFRP with stepped drills, The 
international journal of advanced manufacturing 
technology. doi: 10.1007/s00170-018-1981-2 
[5] Li M, Leung Soo S, Aspinwall DK et al. (2018) Study on 
tool wear and work piece surface integrity following 
drilling of CFRP laminates with variable feed rate strategy, 
Science di-rect procedia CIRP 71, 407-412. 
[6] Turki Y, Habac M, Velasco R et al. (2014) Experimental 
investigation of drilling damage and stitching effects on 
the mechanical behavior of carbon/epoxy composites, 
International journal of machine tools and manufacture 87, 
61-72. 
[7] Feito N, Diaz-Alvarez J, Cantero JL et al. (2015) Influence 
of special tool geometry in drilling woven CFRPs 
materials, Science direct procedia engineering 132, 632-
638. 
[8] Feito N, Diaz-Alvarez J, Diaz-Alvarez A et al. (2014) 
Experimental analysis of the influence of drill point angle 
and wear on the drilling of woven CFRPs, Materials 7, 
4258-4271. doi: 10.3390/ma7064258. 
[9] Turki Y, Habak M, Velasco K et al. (2014) Influence of 
cutting forces and damage on 2D and 3D carbon/epoxy 
composite in drilling.  
doi: 10.4028/www.scientif.net/KEM.611-612.1217. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


Experimental analysis of the defects of drilling woven CFRP

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Experimental analysis of the defects of drilling woven CFRP

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