The document is a project seminar submitted by Mr. Rahul Raju Kundiya on the topic of experimental analysis and modelling in micro drilling of CFRP-Ti6Al4V stacked composite materials. It discusses micro drilling, the objectives of the study, experimental setup, design of experimentation, results and discussion. The study aims to design experiments to analyze the effect of drilling parameters on hole quality and develop a mechanistic force model. It presents results on hole taper, radial overcut, delamination factor and burr formation when drilling the composite material stack at different speeds and feed rates.

1. A
Project seminar
On
Experimental Analysis and Modelling in Micro drilling of
CFRP-Ti6Al4V Stacked Composite
Submitted By
Mr. Rahul Raju Kundiya (2030332608001)
Under the Guidance of
Dr. R. S. Pawade
1
DEPARTMENT OF MECHANICAL ENGINEERING
Dr. Babasaheb Ambedkar Technological University, Lonere
1

2. Contents
 Introduction
 Literature Survey
 Objectives
 Micro Drilling
 Tooling and Work material
Theme of Experimentation
 Experimental Setup
 Design of Experimentation
 Mechanistic Force model
 Result and Discussion
 Conclusion
 Future Scope
2

3. Introduction
 Cowling is a covering on vehicle's engine, mostly found on highspeed sports
automobiles and aircraft vehicles. Cowling is used to reduce active
aerodynamic drag and cool engine by directing airflow as an air intake for jet
engines, also cover is used for decorative purposes of outboard motor.
 Ti6Al4V/CFRP stack used in airspace industry for engine cowlings, wings
connection, wing panels, nacelles.
 CFRP/Ti alloy stack of about 0.8 mm thick sheet is used for cowling of high
performance engine of 757 Dreamliner, Falcon 900 business jet, Airbus A320,
F-16XL aircraft.
3

4. Micro Drilling
 Micro drilling is one of the most fundamental micro machining techniques and
is generally defined as the drilling of diameters between 1 micron and 1 mm.
Different researchers and manufacturers define micro drilling differently.
Sphinx, the Swiss micro drill manufacturer, defined micro drilling as having a
starting diameter of 0.05 mm and ranging to 2.5 mm.
 Micro drills are typically made of either cobalt steel or micro grain tungsten
carbide. The drill point angle is based on the material to be drilled. The normal
point angle is 118 degrees and 140 degrees is used for hard materials. The
larger included point angle provides more strength at the drill point.
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5. Summary of Literature Survey
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6. Continue
 Delamination- Delamination factor decreased with decreasing feed. It
resulted due to the influence of micro-drilling size effect where specific
cutting forces increased non-linearly on downscaling of feed in CFRP
composite material.
 Tool Wear- Smaller drill bit always face a problem of dissipating heat slower
than larger drill bits. At substantial speeds, there was a possibility of very high
temperature development. It produced micro-fractures and increased tool
wear.
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7. Continue
 Hole Quality- Higher feed rate increased induce higher dynamic vibrations in
the machining zone. Due to length of the uncut chip thickness increased in
turn increased the ploughing component of the cutting force. This increased
ploughing component increases the circularity error.
 Burr formation- material deformed due to the effect of the point angle. The
distance between deformation starts and exit surface was affected by the thrust
force. Depending on the increased in thrust force which caused burrs to
increased at the exit point. Burr height increased at exit surface parallel to the
increased in feed rate. increased in spindle speed caused to chip height to
decreased at both entry and exit points
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8. Continue
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Thrust force- rise in feed rate caused an increased in chip section lifted in unit
time. This caused an increased in load affecting the cutting tool.
Torque- friction and chips sticking to the tool caused the chip to jam inside the hole
which affect higher torque value.
In addition to the size requirements, the micro holes require no taper or minimum
taper. When the diameter of the entrance hole is greater than exit hole. thus, taper
were positive.

9. Objectives
 To design the experimentation using RSM CCD customize design for
mechanical micro drilling of Ti6Al4V/CFRP Stack Composite.
 To study the effect of drilling parameters on hole quality in term of
delamination factor, hole taper, radial overcut and burr characteristics.
 To develop mechanistic force model to determine the lateral, thrust and
cutting forces.
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10. Tooling and Work material
 Ti6Al4V (X ray- Spectroscopy Titanium Gr.5) 0.5mm thick
 Chemical Composition- Ti-89.46%, Al-6.01%, V-4.06%, Fe- 0.24%
 CFRP 16 fibric plies of ‘sigratex CE 8204-65-42’ prepregs. Woven with
twill 2/2 wave and epoxy resin.
 Composition - Fiber volume 53.5- 54.7% and rest is epoxy resin.
 Tool Material T5401 grade – TiN coated Tungsten carbide (Coating
thickness 0.2-0.5 micron)
 Twist Drill- Dia-400µ, Helix angle 30 degrees, Clearance angle- 10
degrees, Web thickness 26µ, chisel edge angle 140 degrees, Tool edge
radius 2-2.5µ
9

11. Theme of Experimentation
10
 The drilling parameters are spindle Speed, feed Rate (variable),diameter and
drill steps (fixed). The quality of holes was determined in terms of hole taper,
radial overcut and delamination factor. In addition the burrs formed while micro
drilling was measured.

12. Design of Experimentation
 Design of Experiments is used to determine the appropriate number of tests
and the experimental conditions necessary to obtain the desired goal of
analyzing which factors of the process influence the response variable.
Table 1. Experimental design factor
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13. Design of Experimentation
 RSM CCD Method
 A simple function, such as linear or quadratic polynomial, fitted to the data
obtained from the experiments is called response surface, and the approach is
called the response surface method.
 It is a collection of statistical and mathematical techniques useful for
developing, improving, and optimizing processes. It is a method for
constructing global approximations to system behavior based on results
calculated at various points in the design space.
 A CCD is an experimental design, useful in response surface methodology, for
building a second order model for the resposnse variable without needing to
use a complete three level factorial experiment.
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14. Continue
 Customized Multilevel multifactorial screening design is used to identify
main effects under consideration of average levels of other factors.
 Mixed multilevel screening design suggested 20 runs for 3 factors and mixed
2,3,4 levels. Screening orthogonal arrays analysts simplifies the analysis and
interpretation of results.
 They obtain a lot of information about the main effects in a relatively few
number of runs. It can test whether non-linear terms are needed in the model,
at least as far as the three-level factors are concerned.
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15. Experimental Setup
 The experimental setup was used for performing the experiments is CNC
Micromachining station made by Interface design associates pvt. limited.
 Aerostatic spindle provided 6001 rpm to 60000 rpm capacity. Preliminary
micro hole making operations are performed by varying various spindle speed
and result limited to higher rpm of varying from 25000, 35000 and 45000 rpm
due to insufficient longitudinal strength and breakability of tools.
 Experimentation is planned in these section of Ti6AlV4 & CFRP and
CFRP/Ti6AlV4 stack due to its anisotropic property in application.
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16. Continue
Fig. Interface, SMD10B
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17. Continue
 Optical 3D surface measurement device and a form measurement device.
 Form and roughness measurement.
 Measurement of materials with varying reflection properties.
 Measurement of areas and volumes in a vertical resolution of up to 10nm.
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18. Result and Discussion
 In this work, micro drilling of CFRP-Ti stacked composite was carried out. In
particular the quality of holes drilled have been examined in terms of hole
taper, radial overcut and delamination factor by using statistical design of
experiments. In addition burr formed were characterized for their nature and
type. In the last part, mechanistic force model is discussed that determine the
cutting, thrust and friction force generated during micro drilling.
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19. Continue
 Analysis of micro holes
Table 2. Drilling holes at different drilling condition
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20. Continue
Table 3. CCD design layout and experimental results
19

21. Analysis of hole taper
 Hole taper is one of the inherent manufacturing problems associated with micro drilling.
A taper is defined as the uniform change of the diameter of a workpiece on its axis. The
quality of micro holes is determined by the taper of holes.
Table 4. ANOVA of hole taper
 The model F-value of 3.13 implies that the model is significant relative to the noise.
There is a 2.56 percentage chance that an F-value this large could occur due to noise. P-
values less than 0.0500 indicate the model terms are significant.
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22. Continue
 Normal probability plot of residuals for hole taper
 The point on this normal probability plot
form a nearly indicates that the normal
distribution is a good model for data set.
 The normal probability plot of the residuals
is approximately linear supporting the
condition that the error terms are normally
distributed.
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23. Response surface plots for taper
 Hole taper is one of the inherent
manufacturing problems associated with
micro drilling. In order to achieve the
greater accuracy in micro drilling process
taper should be minimum. Therefore,
parameters affecting the taper are
essential to recognize.
 Figure shows the influence of spindle
speed and feed rate on hole taper.
Minimum taper occurs for a middle level
of spindle speed and minimum level of
feed rate. It can be noticed that middle
level of spindle speed is the best for lower
taper.
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24. Continue
 The estimated surface response for
taper in relation to spindle speed and
MQL flow rate is shown in figure.
 It can be seen that minimum taper
occurs for a minimum level of MQL
flow rate and near to the middle level
of spindle speed. It can be noticed
that higher level of spindle speed
produced maximum hole taper.
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25. Continue
 Figure shows the effect of feed rate
and MQL flow rate on taper.
 It is clear that the minimum taper
occurs for near to the middle level of
feed rate and middle level of MQL
flow rate and also note that the
middle level of both factors are good
condition for lower taper but less
value of feed rate is good for the
minimum the size of hole taper.
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26. Continue
 The one factor effect plot for hole taper has
been depicted in figure 4.6. The one factor
plot helps in predicting the behavior of
each output by changing the respective
input parameter.
 It can be noticed that increases the spindle
speed from 26591 rpm to 43409 rpm
results in decreased hole taper. The
increasing feed rate also resulted in
increased hole taper and also increasing
MQL flow rate results in decreased hole
taper.
25

27. Effects of drilling parameters on
hole taper
 According to trend of graph, Spindle speed has tremendous effect on the machining
quality. The higher the feed and spindle the rougher the surface of the hole. Spindle
speed improved stiffness of drill due to self-piloting nature and higher stability of drill
bit at higher speeds which get resulted in better circular holes that is minimize the taper
hole.
 In higher MQL flow rate condition the average taper values were positive, the diameter
at the entrance of the holes were bigger than at the outlet. These is due to the fact that
radial vibrations of the drill bit are present to the greater extent at the entry rather than
the exit.
 The effect of MQL was remove debris from machining zone and thus avoids any built-
up edge formation. It dissipates the heat efficiently, avoiding thermal softening effect.
Circularity is minimum at lower feed rate and increases gradually as increase in feed
rate. This could be attributed due to increase in force required to fracture of fiber at
higher feed rate in CFRP.
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28. Analysis of Radial Overcut
 Radial overcut is the increases in the radius of the drilled hole compared to the tool
diameter. The qualiy of micro holes determined by radial overcut. During the high
spindle speed and maximum feed rate machining condition forming numerous
micro craters, recast layer which assists in increasing the surface area of radial
overcut.
Table 5. ANOVA of ROC
 The model F-value of 3.698 implies that the model is significant relative to the
noise. There is a 3.98 percentage chance that an F-value this large could occur due
to noise.
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29. Continue
 Normal probability plot of
residuals for hole taper
 Then test of the normality assumptions of the
data is conducted and it can be seen in Figure
that all the points on the normal plot come
close to forming a straight line. This indicates
that the data are fairly normal and there is no
deviation from the normality.
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30. Response surface plot for ROC
 Radial overcut is the inherent parameter to
the micro drilling process which is
unavoidable though suitable compensations
are provided at the tool design. In order to
achieve the greater accuracy in mechanical
micro drilling process overcut should be
minimum. Therefore, parameters affecting
the overcut are essential to recognize.
 Figure shows the influence of spindle speed
and feed rate on radial overcut. Minimum
radial overcut occurs for middle level of
spindle speed and a minimum level of feed
rate. It can be noticed that minimum level
of feed rate is best for lower radial overcut.
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31. Continue
 The estimated surface response for
radial overcut in relation to spindle
speed and MQL flow rate shown in
figure
 It can be seen that minimum radial
overcut occurs for amaximum level
of MQL flow rate and near to the
middle level of spindle speed. It can
be noticed that higher level of spindle
speed gives maximum the radial
overcut.
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32. Continue
 Figure shows the effect of feed rate
and MQL flow rate on radial overcut.
 It is clear that the minimum radial
overcut occurs for near to the
minimum level of feed rate and
higher level of flow rate and also note
that the middle level of spindle speed
are the suitable condition for lower
radial overcut. It is cleared that radial
overcut depends more on feed rate
than on flow rate and spindle speed.
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33. Continue
 The one factor effect plot for radial
overcut has been depicted in figure.
 The one factor plot shows the linear
effect of changing the level of a
single factor. It can be noticed that
increases the spindle speed from
26591 rpm to 43409 rpm results in
increased radial overcut. The slightly
increasing feed rate also resulted in
decreased radial overcut and also
decreasing MQL flow rate results in
increased radial overcut.
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34. Effects of drilling parameters on
ROC
 According to trend in graph, Spindle speed is directly proportional to the centrifugal
force acting on the lubrication fluid present in the gap between tool and workpiece,
which contains debris particles. Therefore, when the spindle speed increases, result
minimize radial overcut. When increment in feed rate with increase in spindle speed
attributed to the higher friction between tool and workpiece. Therefore, produce high
heat generation and wear leads to the occurrence of larger radial overcut.
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35. Analysis of delamination factor
 Drilling is the most frequently used operation for assembly of structures or components
but the composite damage called delamination is also associated with drilling composite
laminates. Delamination is one of the major problems encountered in drilling of
composite laminates as compared to that of metals.
Table 6. ANOVA of delamination factor
 The model F-value of 3.452 implies that the model is significant relative to the noise.
There is a 3.06 percentage chance that an F-value this large could occur due to noise.
34

36. Continue
 Then test of the normality
assumptions of the data is conducted
and it can be seen in Figure that all
the points on the normal plot come
close to forming a straight line. This
indicates that the data are fairly
normal and there is no deviation from
the normality.
35

37. Response surface plot for
delamination factor
 Delamination is one of the inherent
manufacturing problems associated with
micro drilling of composites material. In
order to achieve the greater accuracy in
micro drilling process delamination should
be minimum. Therefore, parameters
affecting the delamination factor are
essential to recognize.
 Figure shows the influence of spindle
speed and feed rate on delamination factor.
Minimum delamination factor occurs for
middle level of spindle speed and a middle
level of feed rate. It can be noticed that
middle level of feed rate is the best for
minimum delamination factor.
36

38. Continue
 The estimated surface response for
delamination factor in relation to spindle
speed and MQL flow rate is shown in
figure.
 It can be seen that maximum delamination
factor occurs for a maximum level of
spindle speed and near to the middle level
of MQL flow rate. It can be noticed that
lower level of feed rate maximize the
delamination factor.
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39. Continue
 Figure shows that effect of feed rate and
MQL flow rate on delamination factor.
 It is clear that the minimum radial overcut
occurs for the minimum level of feed rate
and near to the higher level of MQL flow
rate and also note that the middle level of
spindle speed are better condition for
lower delamination factor. It is clear that
the delamination factor depends more on
spindle speed and feed rate than on flow
rate.
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40. Continue
 The one factor effect plot for delamination
factor has been depicted in figure.
 The one factor plot constructed by
predicting the responses for the low and
high levels of a factor. It can be noticed
that increases the spindle speed from
26591 rpm to 43409 rpm results in
decreased delamination factor. The
increasing feed rate also resulted in
decreased delamination factor and also
increasing MQL flow rate results in
decreased delamination factor.
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41. Effects of drilling parameter on
delamination
 According to trend of graph, Increased in spindle speed and drill diameter minimizes
delamination factor and circularity error, whereas increase in feed rate increases
delamination.
 Feed rate and drill diameter make the largest contribution to delamination damage and
becomes more prominent with the increase of tool wear. The rise in spindle speed
minimizing delamination tendency, therefore it reduces circularity error mainly
affected due to reduction in vibration effect of drill bit and machine.
 Delamination was occurs due to the the separation of adjacent composite plies and
characterized by the formation of inter laminar cracks in CFRP. This damage occurs
during drilling, on the hole entrance (peel-up delamination).
 At high feed, the tool enters the work faster, thus increasing the thrust force. The
quicker passage of the tool damages the inward surface decreases the surface
roughness
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42. Regression equation
 Taper = 4.48633 − (0.000022 × A) + (0.578648 × B) + (0.000784 × C)
 ROC = 26.26529 − (0.000031 × A) − (3.69122 × B) − (0.029813 × C)
 Fd = 1.46381 − (0.000022796 × A) − (0.012173 × B) + (0.000011 × C)
 Where, A = Spindle speed, B = Feed rate and C = MQL flow rate
41

43. Burr formation
 Formation of burrs at entrance is caused by lateral extrusion action and at the exit by
rubbing the margins of the drill. In drilling, the burr that forms at the entrance of the
hole can be a result of tearing, a bending action followed by clean shearing, or lateral
extrusion.
 The burrs can have different shapes, however, there are three basic types of burr shapes
as 3 different types of burr shapes that usually form during micro drilling .
 These are the ideal case with a very little burr formation, uniform, transient and crown
burrs. The uniform burr has relatively small and uniform burr height and thickness
around the hole periphery.
 The crown burr has a larger and irregular height distribution around the hole.
 The transient burr is a type of burr formed in the transient stage between the uniform
and the crown burrs.
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44. Continue
Table.7 Types of burr
43

45. Mechanistic Force Model
 Point angle: 140 degrees , Half point angle (ϕ): 70 degrees =
1.22173 rad
 Helix angle (α): 30 degrees = 0.52359 rad
 Half web thickness (w): 0.0075 mm and Full web thickness =
0.015 mm
 Drill diameter: 0.1 mm or 400 microns
44

46. Continue
45

47. Continue
 Assumption
 For the calibration of the model, cutting forces of rotational reference frame are
transformed to the inertial frame of reference where force measurements are performed.
Although geometrically drill bits are similar in both conventional and micro-drilling,
the chip thickness is comparable to the cutting tool edge radius in case of micro-drilling.
Round cutting edge is considered in micro-drilling (Fig. (c)) instead of sharp cutting
edge assumption of conventional drilling (Fig. (b)) for the development of mechanistic
cutting force model.
46

48. Model calibration
 The coefficients (a0 −a4 and b0 −b4) are calibrated by designed experiments.
Considering the normal rake angle, speed along cutting lip are changing with respect to
radius, the coefficients for the specific normal and friction forces are calibrated with the
cutting lip by dividing it into a series of elemental segments with variable normal rake
angle and cutting speed. The cutting action of cutting lip is separated from that of chisel
edge by a pilot hole which is equal to or a bit larger than the chisel edge length.
 After performing regression analysis on the results of the calibrated drilling
experiments, the coefficients obtained for the specific normal and friction force are
shown in table 8.
Table 8. Coefficient of cutting forces
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49. Continue
Table 9. Calculations of cutting, Lateral and Thrust Forces
48

50. Conclusion
 Work on Micro Drilling of Ti6Al4V/CFRP Stack Composite is inadequate. In above experiment the results
we get that entry diameter is greater than exit diameter thustaper were positive.
 When tool reached end of the holes the diameter decreased, due to the alignment of the tool caused by the
wall. Another important factor determining machining quality is feed rate. At medium spindle speed, feed
rates must be low for good machining quality. However very high spindle speed, high feed rate can be
adopt it has no significant effect on overall machining quality.
 It is observed that higher point angle produces minimum hole delamination than small point angle. The
material used for the stacking i.e Aeroldite is suitable for microdrilling of Titanium CFRP composite with
proper lubrication.
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51. Continue
 In this study, an attempt was made to apply response surface methodology for prediction of
taper, radial overcut and delamination factor in mechanical micro drilling of CFRP/Ti6Al4V
stack composite. Twenty experiments were conducted successfully for three input parameters
at three levels as per central composite design (CCD) method.
 ANOVA results show that spindle speed and feed rate are highly significant parameters, while
MQL flow rate are non-significant parameters by considering taper and radial overcut
responses. For delamination factor, ANOVA results show that MQL flow rate and feed rate are
highly significant parameters, while spindle speed are non-significant parameters.
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52. Continue
 From the response surface plots, it is cleared that lower level of feed rate an
medium level of spindle speed minimizes the taper considerably. It is observed that
higher level of MQL flow rate and medium level of spindle speed minimizes the
taper considerably and also it is cleared that medium level of feed rate and medium
level of spindle speed minimizes the delamination factor considerably.
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53. Continue
 From the mechanistic mathematical model, It was found that minimum cutting, lateral
and thrust forces gotten in seventh experimental run condition (spindle speed = 26591
rpm, feed rate = 1.03). and also maximum cutting, lateral and thrust forces gotten in 8 th
experimental run condition (spindle speed = 26591 rpm, feed rate = 1.03). It was
determined minimum and maximum cutting force 13.5168 Kgf and 24.8847 Kgf. Also
min. and max. lateral force 0.3246 Kgf and 0.5451 Kgf. It was determined minimum and
maximum thrust force 2.8894 Kgf and 4.6673 Kgf.
 Cutting force is always greater than thrust force. The cutting forces increases as the feed
increases and rake angle decreases. Deeper cuts remove more materials, thus requiring
higher cutting force.
52

54. Future Scope
 Mechanical micro drilling on cowling sheet of CFRP/Ti6Al4V stack material
will created interest in Aerospace industries due to micro hole design and its
pattern performance during air suction from cowling sheet to reduce skin drag
friction.
 Structural aircraft researcher will be interested to modify airfoil shape of
cowling and micro hole pattern on cowling sheet.
 Optical researcher can make interest to find effect of light heat source on micro
holes of Metal fiber laminate of CFRP/Ti6Al4V composite.
 Metallurgy research scholars can be interested to implement on metal laminated
fiber material and developing new composition grades by testing mechanical
properties.
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56. Thank you.....
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