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Application of 3D printed ABS based conductive carbon black composite sensor in void fraction measurement
Accepted Manuscript Application of 3D printed ABS based conductive carbon black composite sensor in void fraction measurement Jayanth N, Senthil P PII:
S1359-8368(18)32743-4
DOI:
10.1016/j.compositesb.2018.09.097
Reference:
JCOMB 6067
To appear in:
Composites Part B
Received Date: 23 August 2018 Revised Date:
14 September 2018
Accepted Date: 28 September 2018
Please cite this article as: N J, P S, Application of 3D printed ABS based conductive carbon black composite sensor in void fraction measurement, Composites Part B (2018), doi: https://doi.org/10.1016/ j.compositesb.2018.09.097. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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ABS – CB conductive
Thermal Characterization
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3D printing filament
Void Fraction Measurement
3D Printing of Sensors
ACCEPTED MANUSCRIPT Application of 3D printed ABS based conductive carbon black composite sensor in void fraction measurement Jayanth N, Senthil P*
620015, India.
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Abstract
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Department of Production Engineering, National Institute of Technology, Tiruchirappalli,
The application range of fused deposition modeling (FDM) process has been increased by the
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introduction of multifunctional materials. These materials exhibit enhanced mechanical and thermal properties. In addition to that, some materials like graphene, carbon nanotubes and carbon black have the conductive properties and can be used in electronic applications. In this research work acrylonitrile butadiene styrene (ABS) based carbon black (CB) filament is used for three dimensional (3D) printing the low cost concave capacitive sensor and it is used
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to measure the void fraction of the two-phase flow. The capacitance values for different void fractions are measured using 3D printed sensor and compared with the copper sensor. Also,
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the effect of parameters such as thickness and width of sensors on capacitance values are studied, and a prediction model using regression analysis is developed and validated to find
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the void fraction value. Analysis of variance (ANOVA) is done to find the significant factors affecting the capacitance values obtained for different void fraction values. Keywords: Fused deposition modeling, carbon black, concave capacitive sensor, two-phase flow, void fraction
*
Corresponding author: [email protected]
ACCEPTED MANUSCRIPT Nomenclature fused deposition modeling
ABS
acrylonitrile–butadiene styrene
CB
carbon black
3D
three-dimensional
ANOVA
analysis of variance
GO
graphene oxide
UV
ultra violet
PLA
polylactic acid
3DE
three dimensional disc electrode
PP
polypropylene
PCL
polycaprolactone
SLS
selective laser sintering
MAH
maleic anhydride
EPDM
ethylene-propylene-diene rubber
CNT
carbon nanotubes
EMI
electromagnetic interference
DSC
differential scanning calorimetry
DTG
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TGA
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FDM
Thermogravimetric analysis derivative thermogravimetric
ACCEPTED MANUSCRIPT 1. Introduction The FDM process is one of the low cost and environment-friendly 3D printing processes which make use of a thermoplastic polymer as a raw material in the form of
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filaments. The FDM 3D printed parts are mostly used in making prototypes and functional models for medical and automobile applications [1, 2]. The advantage of FDM is that any complex shape can be 3D printed at a cheaper cost. The disadvantage of the FDM process is that the 3D printed parts have the least strength when compared to parts made by a
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conventional process like injection molding and the variety of materials used is less. Also, the
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application range is very limited, but the introduction of multifunctional materials increased the application range of FDM. The strength of FDM parts can be increased by optimization of parameters or by reinforcement of polymer materials [3, 4]. The graphene, carbon black and carbon nanotubes are multifunctional materials which can be used as nanofiller to improve mechanical, thermal and electrical properties of polymers [5-7]. 3D printable ABS
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and PLA based graphene composites with different compositions were prepared by chemical reduction of graphene oxide (GO) using hydrazine. It was found that the electrical
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conductivity increases with an increase in graphene loading for hot pressed rectangular composite samples. But for the 3D printed samples, electrical conductivity was less when
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compared to hot pressed samples due to the internal voids. The presence of graphene was proved by Raman spectra and ultraviolet (UV) visible spectra of the composites. Also, it was concluded that the thermal and thermomechanical properties of poly lactic acid (PLA) and ABS were improved by the reinforcement of graphene [8]. Graphene-based PLA filament was used as raw material for printing 3D disc electrode (3DE) using FDM process, and from the electrochemical and physicochemical characterization, it was found that the 3DE can be used as an alternative to the Li-ion based setups and platinum electrodes as it has the ability to produce hydrogen. Hence it can be used for making energy storage devices and solid state
ACCEPTED MANUSCRIPT super capacitors [9, 10]. Also, it was used in the 3D printing of anisotropic heat distribution materials [11]. The addition of GO improves mechanical properties and also changes the rheology of
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geopolymer and make it suitable for 3D printing of conductive ceramic composite [12]. Polypropylene (PP) based CB conductive composite was prepared using a single screw extruder, and characterization results show that it is suitable for 3D printing electrical circuits using FDM. Also, it had higher thermal stability when compared with PLA graphene and
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polycaprolactone (PCL) - CB composite [13]. The reinforcement of graphene into ABS
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improved the dynamic storage moduli and elastic modulus. Further, the addition of graphene decreased the breaking stress and strain of FDM 3D Printed ABS [14]. The addition of CB prevented the degradation of ABS, and the thermal stability of ABS/CB composite increased with increase in CB content. But impact strength decreased with the addition of CB [15]. The mechanical and thermal properties of ABS such as hardness, modulus of rigidity, heat
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deflection temperature and ultraviolet stability increased with the addition of CB, but the impact strength and flexural strength decreased [16]. The flexural modulus of Nylon-12
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processed using selective laser sintering (SLS) process decreased by addition of CB nanofillers. But the conductivity increased by loading of CB [17]. The PCL based CB
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composite electronic sensors were printed using low-cost FDM 3D printer and used in applications such as measuring displacement, health monitoring systems, etc [18]. CB based ABS composite was prepared by using maleic anhydride (MAH) functionalized ABS as a compatibilizer and ethylene-propylene-diene rubber (EPDM) as flexibilizer which improved the tensile strength, impact strength and elongation at break along with the reduction in the resistivity [19]. Graphene-based polymer composite was used as a lossy sheet in a three-layer panel of dielectric salisbury screen which is used as a radar absorbing materials [20]. Conductive composites such as PLA- graphene, ABS-carbon nanotubes (CNT), etc. were 3D
ACCEPTED MANUSCRIPT printed, and their electromagnetic interference (EMI) shielding performance was measured, and it was found that graphene-based composites exhibited efficient performance. Hence it can be used for making EMI shields for electronic applications [21]. The capacitive sensors made up of copper with helical, concave and double ring configurations were used to
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measure the volumetric concentration of two-phase air-water flows and found that double ring as the most suitable configuration because it is less affected by the gas-liquid distribution [22]. The copper-based concave capacitive sensor was used to measure the void fraction of
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liquid-gas and liquid-liquid two-phase flow, and it was found that a change in capacitance
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value is sufficient and measurable [23].
In this research work, for the first time the application of FDM based 3D printed sensor in void fraction measurement of two-phase flow is reported. The ABS-CB conductive filament has been used as a model material as it is least costlier when compared to graphenebased composites and it is thermally characterized to check the feasibility of using this
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composite in the FDM process. The addition of CB coverts the non-conductive ABS into conductive polymer. Hence, ABS-CB composite can be used for making sensors which can
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be used in electronic applications. The concave capacitive sensors are 3D printed using the conductive ABS-CB filament, and the capacitance values measured are compared with
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sensors made up of copper to check its capability to predict the void fraction of water-air twophase flow. Then the effect of parameters such as width and thickness of sensors on capacitance is also studied and ANOVA is used to find the significant parameter that is mostly affecting capacitance value. The regression analysis is used to develop a predictive model to find the void fraction from the capacitance value measured and it is validated using experimental values.
ACCEPTED MANUSCRIPT 2. Experimental 2.1. Materials In this research work commercially available ABS based conductive carbon black
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(ABS-CB) filament of 2.85mm diameter is used as a model material for 3D printing. Ultimaker 3 extended 3D printer with dual nozzle system is used for making the concave capacitive sensors. The copper tape of 50 mm width and 0.125 mm thickness was used as a capacitive sensor to compare the capability of 3D printed sensor. Transparent acrylic pipe of
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350 mm length, 54 mm inner diameter and 3mm wall thickness is used for experimentation.
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2.2. Characterization 2.2.1. Differential scanning calorimetry
A Perkin-Elmer Pyris 6 differential scanning calorimeter (DSC) (Waltham, MA, USA) is used for the DSC analyses. All the analyses were performed under nitrogen flow (20
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ml/min). The ABS and ABS-CB composite samples (2-5mg) were analyzed from 30–150ºC at a heating rate of 5 ºC/min. The DSC curves for ABS and ABS-CB composite are shown in Fig. 1. The glass transition temperature (Tg) of pure ABS is obtained at nearly 102 ºC, and it
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is increased to a value of 120 ºC for ABS-CB composite. Hence the addition of CB improves
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Tg value of ABS. For FDM process Tg value of 3D printing material is important to decide the printing conditions such as bed temperature, nozzle temperature, etc. In this experiment bed temperature of 80 ºC is used while printing ABS-CB which is less than the Tg value. So the distortion of samples doesn’t occur.
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Fig. 1 - DSC curves for ABS and ABS-CB composite. 2.2.2. Thermogravimetric analysis
Thermogravimetric analysis (TGA) was used to investigate the thermal properties of
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pure ABS and ABS-CB composite. The nature and extent of degradation of the polymers are given by TGA and derivative thermogravimetric (DTG) thermograms. TGA is carried out in a Perkin-Elmer Pyris 6 TGA thermogravimetric analyzer (Waltham, MA, USA). Nitrogen
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was used as the purge gas at a flow rate of 20 ml/min. The samples (2–5 mg) were analyzed
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from 30–800º C at a heating rate of 10 ºC/min. The weight loss curves of ABS and ABS-CB composite shown in Fig. 2(a) reveals that after heating to 800º C, the remaining residue weight is 16.47% for ABS-CB but pure ABS completely degrade at 489º C. This indicates that the CB loading is almost 16%. The TGA results are given in Table 1. The onset temperature (Tonset) of degradation for pure ABS is 376.16 ºC, and it shifts to 369 ºC for ABS-CB composite. The addition of CB increased the degradation temperature at 20% weight loss (T20%wt) from 418.83 ºC to 441.83 ºC and the degradation temperature at 50% weight loss (T50%wt) is shifted from 435.66 ºC to 463.33 ºC. The maximum degradation
ACCEPTED MANUSCRIPT temperature (Tmax) also increased from 438.16 ºC to 456.83 ºC for ABS-CB composite as shown in DTG curve (Fig. 2(b)) Table 1- TGA results of ABS and ABS-CB composite Material
Temperature(ºC) Tonset
T20%wt
T50%wt
Residue (%) Tmax
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Sample No.
ABS
376.16 418.83 435.66 438.16
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2.
ABS –CB
369.00 441.83 463.33 456.83
16.47
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1.
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(b) Fig. 2 (a) TGA and (b) DTG curves for ABS and ABS-CB composite.
ACCEPTED MANUSCRIPT 2.3. 3D printing of sensors The ABS-CB filament is printed in the form of sheets of length 94 mm with uniform printing parameters such as layer thickness of 0.2 mm, a nozzle temperature of 230 ºC, bed temperature of 80 ºC and concentric infill pattern. Totally 9 sets of capacitive sensors are
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printed by varying width and thickness as given in Table 2. The 3D printed ABS-CB sheets
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of different widths are shown in Fig. 3.
(b)
(c)
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Fig. 3 3D printed ABS-CB sheet with a width of (a) 30 mm, (b) 50 mm and (c) 70 mm Table 2- Dimensions of the 3D printed specimen
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Specimen No. 1 2 3 4 5 6 7 8 9
Width (W) mm 30 30 30 50 50 50 70 70 70
Thickness (T) mm 0.2 0.4 0.6 0.2 0.4 0.6 0.2 0.4 0.6
ACCEPTED MANUSCRIPT 2.4. Capacitance measurement The experimental setup for void fraction measurement of water-air two-phase flow is shown in Fig. 4 which consists of transparent acrylic pipe enclosed on both sides by acrylic sheets and a ruler is attached on one side to measure the fluid level. The inlet and outlet are
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made diametrically opposite to each other for filling and draining of the fluid respectively. The 3D printed ABS-CB electrodes are pasted using adhesive tape on the middle portion of the pipe in the form of parallel concave capacitors with a gap of 0.2 mm. A small piece of
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copper tape is pasted on the ABS-CB electrodes for soldering the wires which act as a terminals for capacitance measurement. Then the setup was mounted horizontally on the
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wooden stand with leveling screws which are adjusted to make the setup flat using a bubble level. In this experiment, void fraction for air-distilled water two-phase flows are measured using both copper sensor and 3D printed ABS-CB sensor. The key sight technologies E4990A Impedance Analyzer with a frequency range of 20 Hz to 120 MHz was used to
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measure the change in capacitance value corresponding to the level of the liquid. All the capacitance values are measured at a constant frequency of 2 MHz. The capacitance value (C) is measured for void fraction of 0%, 25%, 50%, 75% and 100%. The water level for the
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corresponding void fraction is calculated using the following formula [24]. Area of gas (A G ) Total cross-sectional area (A G +A L )
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Void fraction (V) =
(1)
As we know the void fraction, diameter of the pipe (dp) and the total cross-sectional area, the area of gas (AG) and area of liquid (AL) can be calculated. The water level, i.e. height of the liquid (HL) for the corresponding void fraction is calculated from the following formula [25].
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d /2-H L d p d d Area of liquid (A L ) = p cos −1 p − − HL 2 p HL − HL2 d p /2 2 2 2
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Inlet
(2)
Funnel
Impedence analyzer
3D printed sensor Leveling screws
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Ruler for level measurement
Outlet
Spirit-level
HL
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Fig. 4- Experimental setup for void fraction measurement of water – air two-phase flow The capacitance values measured using copper and 3 D printed ABS-CB sensors for
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the corresponding void fraction and the water level are given in table 3. The sensors were coded as Cu for copper and 301, 302, 303, 501, 502, 503, 701, 702, 703 for 3D printed ABS-
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CB in which first two digits represent the width of the sensor, i.e. 30 mm, 50 mm and 70mm. The last digit represents the number of layers 1, 2 and 3 which corresponds to the sensor thickness of 0.2 mm, 0.4mm and 0.6mm respectively since layer thickness used for experimentation is 0.2 mm.
ACCEPTED MANUSCRIPT Table 3- Capacitance measurement using copper and 3D printed sensors V
HL
(%)
( mm)
Ccu
C301
C302
C303
C501
C502
C503
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Capacitance (pF)
0
5.30
2.91
3.21
3.38
3.42
3.66
75
16
10.95
3.49
3.74
4.55
4.50
4.84
50
27
13.46
4.05
4.22
5.18
4.95
5.39
25
38
15.96
4.50
4.77
5.75
5.26
0
54
20.66
5.25
5.52
6.53
5.80
C703
4.13
4.30
4.47
5.31
5.37
5.92
6.13
6.07
5.80
6.57
6.73
5.78
6.71
6.19
6.85
7.22
6.37
7.64
6.73
7.73
8.06
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2.5. Response time measurement
C702
3.80
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100
C701
The reponse of the ABS-CB sensor to a step change in void fraction is shown in Fig.
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5. The ABS-CB sheets of width 50 mm and thickness 0.4 mm is taken for demonstration of reponse time. The capacitance value decreases with increase in the void fraction. Hence the fall time is measured for sudden change of void fraction from 25% to 100% and the
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corresponding capacitance values for the initial and final void fractions are 5.82 pF and 4.17
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pF respectively.The fall time (tf) is defined as the time taken for the response to fall from 90% to 10% of the steady-state response.The response time of the 3D printed ABS-CB sensor is found to be 6.9 seconds for a step change in void fraction.Hence it can be used in the void fraction measurement of two-phase flow.
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Fig. 5- ABS-CB sensor response to a step change in void fraction.
3. Results and discussion
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3.1. Comparison of the ABS-CB sensor with copper sensor Initially, a copper tape of 50 mm width and 0.125 mm thickness is used for making
concave capacitance sensor, and the capacitance values (Ccu) for corresponding void fractions are measured using an impedance analyzer and given in table 3. This copper sensor is made as a reference to compare the capability of ABS-CB sensor. Then the ABS-CB composite material is 3D printed in the form of thin sheets using FDM process with same width of 50 mm and thickness of 0.4 mm. The capacitance values (C502) for corresponding void fractions
ACCEPTED MANUSCRIPT are measured five times, and the average values are given in table 3. The capacitance values of the copper sensor vary from 5.30 pF – 20.66 pF, but for ABS-CB sensor the capacitance values (C502) vary from 3.66 pF – 6.37 pF. The variation is less when compared to the copper sensor, but the variation in capacitance values is measurable. The variation of capacitance
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value with the change in the void fraction is given in Fig. 6. The capacitance value decrease with increase in the void fraction for the copper sensor (Fig. 6(a)), a similar trend is obtained for the 3D printed ABS-CB sensor (Fig. 6(b)). Hence ABS-CB can be used as a replacement
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for copper for making concave capacitance sensor.
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(a)
(b)
Fig. 6 – Variation of capacitance value with change in void fraction for (a) copper sensor and (b) ABS-CB sensor
ACCEPTED MANUSCRIPT 3.2. Effect of sensor thickness The ABS-CB sensors are 3D printed by varying thickness with constant width and length. The capacitance value increases with an increase in fluid level or decrease in a void fraction. The Figs. 7(a), (b) and (c) shows the effect of sensor thickness on capacitance values
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at different void fractions for a sensor width of 30 mm, 50 mm and 70 mm respectively. The capacitance value increases with an increase in sensor thickness, this is due to the fact that the increase in sensor volume increase the CB content which in turn reduce the resistance values
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and increase the capacitance values.In all the cases minimum capacitance values are obtained for sensor thickness of 0.2 mm and maximum capacitance values are obtained for sensor
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thickness of 0.6 mm.
(b)
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(c)
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Fig. 7 – Effect of sensor thickness on capacitance value for a width of (a) 30 mm, b) 50mm,
3.3. Effect of sensor width
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and (c) 70mm
The ABS-CB sensors are 3D printed by varying width with constant thickness and
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length. The capacitance value increases with an increase in fluid level or decrease in a void fraction. The Figs. 8 a, b and c shows the effect of sensor width on capacitance values obtained at different void fractions for a sensor thickness of 0.2 mm, 0.4 mm and 0.6 mm
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respectively. The capacitance value increases with an increase in sensor width. This is due to the fact that capacitance is directly proportional to the capacitor area. In all the cases
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minimum capacitance values are obtained for a sensor width of 30 mm, and maximum capacitance values are obtained for sensor thickness of 70 mm.
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(a)
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(b)
(c) Fig. 8 - Effect of sensor width on capacitance value for thickness value of (a) 0.2 mm, b) 0.4 mm, and (c) 0.6 mm
ACCEPTED MANUSCRIPT 3.4. Statistical analysis Analysis of variance (ANOVA) is done to find the significant parameter that affects the capacitance value. In this experiment capacitance values are measured for five void
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fraction values (100%, 75%, 50%, 25%, and 0%). The ANOVA is carried out using Minitab statistical software for all the five void fractions. The sensor width (W) with three levels (30 mm, 50mm, 70mm) and sensor thickness (T) with three levels (0.2 mm, 0.4 mm, 0.6 mm) are taken as input parameters, and capacitance value is the output. The capacitance values for
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nine 3D printed sensors are measured for each void fraction as given in Table 3; totally it is
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45 capacitance values for 5 void fractions. The capacitance values of 3D printed sensors for 100% void fraction is given as a response. The ANOVA results for 100% void fraction are given in Table 4. From the F-value and P-value (P-values < 0.05 are significant) it is confirmed that both the width and thickness of the sensor are the significant factor affecting capacitance value. Similarly, the ANOVA is conducted for the other 4 void fractions, and the
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results show that both the sensor width and thickness are the significant factors affecting capacitance values.
Degrees of
Sum of
Mean squares
F- value
P-value
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Source
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Table 4 - Results of ANOVA for 100% void fraction
freedom
squares
Width(W)
2
1.95709
0.978544
470.96
0.000<0.05
Thickness(T)
2
0.22096
0.110478
53.17
0.001<0.05
Error
4
0.00831
0.002078
Total
8
2.18636
ACCEPTED MANUSCRIPT The regression analysis was carried out using Minitab statistical software by keeping the width as constant and varying the thickness and capacitance value to predict the void fraction. The regression equations obtained for 3 sensor widths are given below.
50 mm sensor: V = 286 - 125 T – 52.4 C + 42.0 T*C 70 mm sensor: V = 259 - 39 T – 38.8 C + 17.9 T*C
(3)
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30 mm sensor: V = 249 - 61.1 T – 53.9 C + 35.9 T*C
(4) (5)
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The R2 value obtained for equation 3 (30 mm width) is 97.6% .The maximum
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deviation of 10.95 and minimum deviation of 0.82 is obtained for 30 mm width. The average deviation of the void fraction is 4.26. The R2 values of 95.6% and 92% are obtained for equation 4 and 5 respectively. The maximum, minimum and average deviation in void fraction of 12, 3.19 and 6.92 respectively are obtained for 50 mm by substituting the thickness and capacitance values. Similarly, the maximum, minimum and average deviation
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in void fraction of 18.90, 1.17 and 8.66 respectively are obtained for 70 mm width. The combined regression equation is obtained by entering all the capacitance readings
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corresponding to the sensor width and thickness. The equation 6 gives the combined regression equation.
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V= 246 + 0.39 W - 108 T - 66.6 C + 56.9 T*C + 0.61W*T + 0.364 W*C – 0.489 W*T*C (6) The R2 value obtained for the combined regression equation is 94.8%. The maximum,
minimum and average deviation in void fraction of 17.56, 0.08 and 6.82 respectively are obtained for the combined regression equation. Hence regression equations obtained can be used to predict the void fraction values for different values of width, thickness and capacitance values of 3D printed sensors.
ACCEPTED MANUSCRIPT 4. Conclusions In this paper, the application of the FDM 3D printed ABS-CB concave capacitive sensor in void fraction measurement is reported for the first time and the variation in capacitance values with a change in void fraction (0-100%) are measured and compared with
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the copper sensor. The capacitance values increase with an increase in water level or decrease in a void fraction. The capacitance values obtained for copper (Ccu) ranges from 5.30 pF – 20.66 pF. The variation in capacitance values of 3D printed ABS-CB sensor with 50 mm
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width and 0.4 mm thickness (C502) is very less, i.e. 3.66 – 6.37 pF when compared to the copper sensor, but it is measurable. Also the response time of this sensor is evaluated as 6.9
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seconds. Hence ABS - CB sensor can be used instead of the copper sensor for void fraction measurement of water – air two-phase flow.
The effect of sensor width and thickness on variation in capacitance values is also studied, and it was found that the capacitance value increases with an increase in width and
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thickness. This is due to the fact that the capacitance value is directly proportional to the sensor area. Hence increase in width increases sensor area which in turn will increase the capacitance value. The increase in width and thickness will also increase the CB content
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capacitance value.
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which in turn will decrease the resistance of the sensor. This also leads to an increase in the
The ANOVA results show that both the sensor width and thickness are the significant
factors that affect the capacitance values for all five void fractions (0%, 25%, 50%, 75% and 100%). The regression equations generated can be used to predict the void fraction from the capacitance value measured. Hence a low-cost FDM 3D printed capacitive sensor can be used as a replacement for a copper sensor for measuring the void fraction of air-water two-phase flow.
ACCEPTED MANUSCRIPT Acknowledgment The authors are thankful to Dr. B. Vasuki, Head of the Department, Instrumentation and Control Engineering, National Institute of Technology, Tiruchirappalli, 620015, India for
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ACCEPTED MANUSCRIPT 17. Athreya SR, Kalaitzidou K, Das S. Processing and characterization of a carbon blackfilled electrically conductive Nylon-12 nanocomposite produced by selective laser sintering. Material Science and Engineering A 2010;527(10):2637-42. 18. Leigh SJ, Bradley RJ, Purssell CP, Billson DR, Hutchins DA. A simple, low-cost
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conductive composite material for 3D printing of electronic sensors. PloS one 2012; 7(11):1-6.
19. Wang F, Hong RY, Feng, WG, Badamid D, Zeng K. Electrical and mechanical
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properties of ABS/EPDM composites filled with carbon black, Materials Letters 2014;125(15): 48-50.
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20. Bellis, Giovanni De. Electromagnetic Absorbing Properties of Graphene – Polymer Composite Shield. Carbon 2014;73:175-84.
21. Viskadourakis Z, Vasilopoulos KC, Economou EN, Soukoulis CM, Kenanakis G. Electromagnetic shielding effectiveness of 3D printed polymer composites. Applied
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Physics A 2017;123:736.
22. Dos Reis E, Cunha DS. Experimental study on different configurations of capacitive sensors for measuring the volumetric concentration in two phase flows. Flow
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Measurement and Instrumentation 2014;37:127–134.
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23. Pal A, Vasuki B. Void Fraction Measurement Using Concave Capacitor Based Sensor – Analytical and Experimental Evaluation. Measurement: Journal of the International Measurement Confederation 2018;124:81–90.
24. Thome JR. Wolverine Heat Transfer Engineering Data Book III, Void Fraction in Two-Phase Flows. http://www.wlv.com/products/databook/db3/DataBookIII.pdf. 25. W.H. Beyer (Ed.), CRC Standard Mathematical Tables, 28th ed. CRC Press, Boca Raton, FL, 1987. p. 125.
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Composites Part B: engineering Highlights •
ABS-CB composite is successfully 3D printed in the form of sheets using FDM process
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and it is used as low cost concave capacitive sensor for measuring void fraction of twophase flow. •
The capacitance values obtained for copper (Ccu) ranges from 5.30 pF – 20.66 pF. The
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variation in capacitance values of 3D printed ABS-CB sensor with 50 mm width and 0.4 mm thickness (C502) is very less, i.e. 3.66 – 6.37 pF when compared to the copper sensor,
•
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but it is measurable.
The effect of sensor width and thickness on variation in capacitance values is also studied, and it was found that the capacitance value increases with an increase in width and thickness.
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The ANOVA results show that both the sensor width and thickness are the significant factors that affect the capacitance values for all five void fractions (0%, 25%, 50%, 75%
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and 100%).
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•
S1359-8368(18)32743-4
DOI:
10.1016/j.compositesb.2018.09.097
Reference:
JCOMB 6067
To appear in:
Composites Part B
Received Date: 23 August 2018 Revised Date:
14 September 2018
Accepted Date: 28 September 2018
Please cite this article as: N J, P S, Application of 3D printed ABS based conductive carbon black composite sensor in void fraction measurement, Composites Part B (2018), doi: https://doi.org/10.1016/ j.compositesb.2018.09.097. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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ABS – CB conductive
Thermal Characterization
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3D printing filament
Void Fraction Measurement
3D Printing of Sensors
ACCEPTED MANUSCRIPT Application of 3D printed ABS based conductive carbon black composite sensor in void fraction measurement Jayanth N, Senthil P*
620015, India.
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Abstract
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Department of Production Engineering, National Institute of Technology, Tiruchirappalli,
The application range of fused deposition modeling (FDM) process has been increased by the
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introduction of multifunctional materials. These materials exhibit enhanced mechanical and thermal properties. In addition to that, some materials like graphene, carbon nanotubes and carbon black have the conductive properties and can be used in electronic applications. In this research work acrylonitrile butadiene styrene (ABS) based carbon black (CB) filament is used for three dimensional (3D) printing the low cost concave capacitive sensor and it is used
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to measure the void fraction of the two-phase flow. The capacitance values for different void fractions are measured using 3D printed sensor and compared with the copper sensor. Also,
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the effect of parameters such as thickness and width of sensors on capacitance values are studied, and a prediction model using regression analysis is developed and validated to find
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the void fraction value. Analysis of variance (ANOVA) is done to find the significant factors affecting the capacitance values obtained for different void fraction values. Keywords: Fused deposition modeling, carbon black, concave capacitive sensor, two-phase flow, void fraction
*
Corresponding author: [email protected]
ACCEPTED MANUSCRIPT Nomenclature fused deposition modeling
ABS
acrylonitrile–butadiene styrene
CB
carbon black
3D
three-dimensional
ANOVA
analysis of variance
GO
graphene oxide
UV
ultra violet
PLA
polylactic acid
3DE
three dimensional disc electrode
PP
polypropylene
PCL
polycaprolactone
SLS
selective laser sintering
MAH
maleic anhydride
EPDM
ethylene-propylene-diene rubber
CNT
carbon nanotubes
EMI
electromagnetic interference
DSC
differential scanning calorimetry
DTG
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TGA
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FDM
Thermogravimetric analysis derivative thermogravimetric
ACCEPTED MANUSCRIPT 1. Introduction The FDM process is one of the low cost and environment-friendly 3D printing processes which make use of a thermoplastic polymer as a raw material in the form of
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filaments. The FDM 3D printed parts are mostly used in making prototypes and functional models for medical and automobile applications [1, 2]. The advantage of FDM is that any complex shape can be 3D printed at a cheaper cost. The disadvantage of the FDM process is that the 3D printed parts have the least strength when compared to parts made by a
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conventional process like injection molding and the variety of materials used is less. Also, the
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application range is very limited, but the introduction of multifunctional materials increased the application range of FDM. The strength of FDM parts can be increased by optimization of parameters or by reinforcement of polymer materials [3, 4]. The graphene, carbon black and carbon nanotubes are multifunctional materials which can be used as nanofiller to improve mechanical, thermal and electrical properties of polymers [5-7]. 3D printable ABS
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and PLA based graphene composites with different compositions were prepared by chemical reduction of graphene oxide (GO) using hydrazine. It was found that the electrical
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conductivity increases with an increase in graphene loading for hot pressed rectangular composite samples. But for the 3D printed samples, electrical conductivity was less when
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compared to hot pressed samples due to the internal voids. The presence of graphene was proved by Raman spectra and ultraviolet (UV) visible spectra of the composites. Also, it was concluded that the thermal and thermomechanical properties of poly lactic acid (PLA) and ABS were improved by the reinforcement of graphene [8]. Graphene-based PLA filament was used as raw material for printing 3D disc electrode (3DE) using FDM process, and from the electrochemical and physicochemical characterization, it was found that the 3DE can be used as an alternative to the Li-ion based setups and platinum electrodes as it has the ability to produce hydrogen. Hence it can be used for making energy storage devices and solid state
ACCEPTED MANUSCRIPT super capacitors [9, 10]. Also, it was used in the 3D printing of anisotropic heat distribution materials [11]. The addition of GO improves mechanical properties and also changes the rheology of
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geopolymer and make it suitable for 3D printing of conductive ceramic composite [12]. Polypropylene (PP) based CB conductive composite was prepared using a single screw extruder, and characterization results show that it is suitable for 3D printing electrical circuits using FDM. Also, it had higher thermal stability when compared with PLA graphene and
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polycaprolactone (PCL) - CB composite [13]. The reinforcement of graphene into ABS
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improved the dynamic storage moduli and elastic modulus. Further, the addition of graphene decreased the breaking stress and strain of FDM 3D Printed ABS [14]. The addition of CB prevented the degradation of ABS, and the thermal stability of ABS/CB composite increased with increase in CB content. But impact strength decreased with the addition of CB [15]. The mechanical and thermal properties of ABS such as hardness, modulus of rigidity, heat
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deflection temperature and ultraviolet stability increased with the addition of CB, but the impact strength and flexural strength decreased [16]. The flexural modulus of Nylon-12
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processed using selective laser sintering (SLS) process decreased by addition of CB nanofillers. But the conductivity increased by loading of CB [17]. The PCL based CB
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composite electronic sensors were printed using low-cost FDM 3D printer and used in applications such as measuring displacement, health monitoring systems, etc [18]. CB based ABS composite was prepared by using maleic anhydride (MAH) functionalized ABS as a compatibilizer and ethylene-propylene-diene rubber (EPDM) as flexibilizer which improved the tensile strength, impact strength and elongation at break along with the reduction in the resistivity [19]. Graphene-based polymer composite was used as a lossy sheet in a three-layer panel of dielectric salisbury screen which is used as a radar absorbing materials [20]. Conductive composites such as PLA- graphene, ABS-carbon nanotubes (CNT), etc. were 3D
ACCEPTED MANUSCRIPT printed, and their electromagnetic interference (EMI) shielding performance was measured, and it was found that graphene-based composites exhibited efficient performance. Hence it can be used for making EMI shields for electronic applications [21]. The capacitive sensors made up of copper with helical, concave and double ring configurations were used to
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measure the volumetric concentration of two-phase air-water flows and found that double ring as the most suitable configuration because it is less affected by the gas-liquid distribution [22]. The copper-based concave capacitive sensor was used to measure the void fraction of
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liquid-gas and liquid-liquid two-phase flow, and it was found that a change in capacitance
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value is sufficient and measurable [23].
In this research work, for the first time the application of FDM based 3D printed sensor in void fraction measurement of two-phase flow is reported. The ABS-CB conductive filament has been used as a model material as it is least costlier when compared to graphenebased composites and it is thermally characterized to check the feasibility of using this
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composite in the FDM process. The addition of CB coverts the non-conductive ABS into conductive polymer. Hence, ABS-CB composite can be used for making sensors which can
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be used in electronic applications. The concave capacitive sensors are 3D printed using the conductive ABS-CB filament, and the capacitance values measured are compared with
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sensors made up of copper to check its capability to predict the void fraction of water-air twophase flow. Then the effect of parameters such as width and thickness of sensors on capacitance is also studied and ANOVA is used to find the significant parameter that is mostly affecting capacitance value. The regression analysis is used to develop a predictive model to find the void fraction from the capacitance value measured and it is validated using experimental values.
ACCEPTED MANUSCRIPT 2. Experimental 2.1. Materials In this research work commercially available ABS based conductive carbon black
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(ABS-CB) filament of 2.85mm diameter is used as a model material for 3D printing. Ultimaker 3 extended 3D printer with dual nozzle system is used for making the concave capacitive sensors. The copper tape of 50 mm width and 0.125 mm thickness was used as a capacitive sensor to compare the capability of 3D printed sensor. Transparent acrylic pipe of
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350 mm length, 54 mm inner diameter and 3mm wall thickness is used for experimentation.
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2.2. Characterization 2.2.1. Differential scanning calorimetry
A Perkin-Elmer Pyris 6 differential scanning calorimeter (DSC) (Waltham, MA, USA) is used for the DSC analyses. All the analyses were performed under nitrogen flow (20
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ml/min). The ABS and ABS-CB composite samples (2-5mg) were analyzed from 30–150ºC at a heating rate of 5 ºC/min. The DSC curves for ABS and ABS-CB composite are shown in Fig. 1. The glass transition temperature (Tg) of pure ABS is obtained at nearly 102 ºC, and it
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is increased to a value of 120 ºC for ABS-CB composite. Hence the addition of CB improves
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Tg value of ABS. For FDM process Tg value of 3D printing material is important to decide the printing conditions such as bed temperature, nozzle temperature, etc. In this experiment bed temperature of 80 ºC is used while printing ABS-CB which is less than the Tg value. So the distortion of samples doesn’t occur.
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Fig. 1 - DSC curves for ABS and ABS-CB composite. 2.2.2. Thermogravimetric analysis
Thermogravimetric analysis (TGA) was used to investigate the thermal properties of
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pure ABS and ABS-CB composite. The nature and extent of degradation of the polymers are given by TGA and derivative thermogravimetric (DTG) thermograms. TGA is carried out in a Perkin-Elmer Pyris 6 TGA thermogravimetric analyzer (Waltham, MA, USA). Nitrogen
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was used as the purge gas at a flow rate of 20 ml/min. The samples (2–5 mg) were analyzed
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from 30–800º C at a heating rate of 10 ºC/min. The weight loss curves of ABS and ABS-CB composite shown in Fig. 2(a) reveals that after heating to 800º C, the remaining residue weight is 16.47% for ABS-CB but pure ABS completely degrade at 489º C. This indicates that the CB loading is almost 16%. The TGA results are given in Table 1. The onset temperature (Tonset) of degradation for pure ABS is 376.16 ºC, and it shifts to 369 ºC for ABS-CB composite. The addition of CB increased the degradation temperature at 20% weight loss (T20%wt) from 418.83 ºC to 441.83 ºC and the degradation temperature at 50% weight loss (T50%wt) is shifted from 435.66 ºC to 463.33 ºC. The maximum degradation
ACCEPTED MANUSCRIPT temperature (Tmax) also increased from 438.16 ºC to 456.83 ºC for ABS-CB composite as shown in DTG curve (Fig. 2(b)) Table 1- TGA results of ABS and ABS-CB composite Material
Temperature(ºC) Tonset
T20%wt
T50%wt
Residue (%) Tmax
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Sample No.
ABS
376.16 418.83 435.66 438.16
-
2.
ABS –CB
369.00 441.83 463.33 456.83
16.47
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1.
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(a)
(b) Fig. 2 (a) TGA and (b) DTG curves for ABS and ABS-CB composite.
ACCEPTED MANUSCRIPT 2.3. 3D printing of sensors The ABS-CB filament is printed in the form of sheets of length 94 mm with uniform printing parameters such as layer thickness of 0.2 mm, a nozzle temperature of 230 ºC, bed temperature of 80 ºC and concentric infill pattern. Totally 9 sets of capacitive sensors are
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printed by varying width and thickness as given in Table 2. The 3D printed ABS-CB sheets
(a)
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of different widths are shown in Fig. 3.
(b)
(c)
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Fig. 3 3D printed ABS-CB sheet with a width of (a) 30 mm, (b) 50 mm and (c) 70 mm Table 2- Dimensions of the 3D printed specimen
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Specimen No. 1 2 3 4 5 6 7 8 9
Width (W) mm 30 30 30 50 50 50 70 70 70
Thickness (T) mm 0.2 0.4 0.6 0.2 0.4 0.6 0.2 0.4 0.6
ACCEPTED MANUSCRIPT 2.4. Capacitance measurement The experimental setup for void fraction measurement of water-air two-phase flow is shown in Fig. 4 which consists of transparent acrylic pipe enclosed on both sides by acrylic sheets and a ruler is attached on one side to measure the fluid level. The inlet and outlet are
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made diametrically opposite to each other for filling and draining of the fluid respectively. The 3D printed ABS-CB electrodes are pasted using adhesive tape on the middle portion of the pipe in the form of parallel concave capacitors with a gap of 0.2 mm. A small piece of
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copper tape is pasted on the ABS-CB electrodes for soldering the wires which act as a terminals for capacitance measurement. Then the setup was mounted horizontally on the
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wooden stand with leveling screws which are adjusted to make the setup flat using a bubble level. In this experiment, void fraction for air-distilled water two-phase flows are measured using both copper sensor and 3D printed ABS-CB sensor. The key sight technologies E4990A Impedance Analyzer with a frequency range of 20 Hz to 120 MHz was used to
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measure the change in capacitance value corresponding to the level of the liquid. All the capacitance values are measured at a constant frequency of 2 MHz. The capacitance value (C) is measured for void fraction of 0%, 25%, 50%, 75% and 100%. The water level for the
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corresponding void fraction is calculated using the following formula [24]. Area of gas (A G ) Total cross-sectional area (A G +A L )
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Void fraction (V) =
(1)
As we know the void fraction, diameter of the pipe (dp) and the total cross-sectional area, the area of gas (AG) and area of liquid (AL) can be calculated. The water level, i.e. height of the liquid (HL) for the corresponding void fraction is calculated from the following formula [25].
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d /2-H L d p d d Area of liquid (A L ) = p cos −1 p − − HL 2 p HL − HL2 d p /2 2 2 2
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Inlet
(2)
Funnel
Impedence analyzer
3D printed sensor Leveling screws
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Ruler for level measurement
Outlet
Spirit-level
HL
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Fig. 4- Experimental setup for void fraction measurement of water – air two-phase flow The capacitance values measured using copper and 3 D printed ABS-CB sensors for
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the corresponding void fraction and the water level are given in table 3. The sensors were coded as Cu for copper and 301, 302, 303, 501, 502, 503, 701, 702, 703 for 3D printed ABS-
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CB in which first two digits represent the width of the sensor, i.e. 30 mm, 50 mm and 70mm. The last digit represents the number of layers 1, 2 and 3 which corresponds to the sensor thickness of 0.2 mm, 0.4mm and 0.6mm respectively since layer thickness used for experimentation is 0.2 mm.
ACCEPTED MANUSCRIPT Table 3- Capacitance measurement using copper and 3D printed sensors V
HL
(%)
( mm)
Ccu
C301
C302
C303
C501
C502
C503
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Capacitance (pF)
0
5.30
2.91
3.21
3.38
3.42
3.66
75
16
10.95
3.49
3.74
4.55
4.50
4.84
50
27
13.46
4.05
4.22
5.18
4.95
5.39
25
38
15.96
4.50
4.77
5.75
5.26
0
54
20.66
5.25
5.52
6.53
5.80
C703
4.13
4.30
4.47
5.31
5.37
5.92
6.13
6.07
5.80
6.57
6.73
5.78
6.71
6.19
6.85
7.22
6.37
7.64
6.73
7.73
8.06
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2.5. Response time measurement
C702
3.80
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100
C701
The reponse of the ABS-CB sensor to a step change in void fraction is shown in Fig.
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5. The ABS-CB sheets of width 50 mm and thickness 0.4 mm is taken for demonstration of reponse time. The capacitance value decreases with increase in the void fraction. Hence the fall time is measured for sudden change of void fraction from 25% to 100% and the
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corresponding capacitance values for the initial and final void fractions are 5.82 pF and 4.17
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pF respectively.The fall time (tf) is defined as the time taken for the response to fall from 90% to 10% of the steady-state response.The response time of the 3D printed ABS-CB sensor is found to be 6.9 seconds for a step change in void fraction.Hence it can be used in the void fraction measurement of two-phase flow.
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Fig. 5- ABS-CB sensor response to a step change in void fraction.
3. Results and discussion
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3.1. Comparison of the ABS-CB sensor with copper sensor Initially, a copper tape of 50 mm width and 0.125 mm thickness is used for making
concave capacitance sensor, and the capacitance values (Ccu) for corresponding void fractions are measured using an impedance analyzer and given in table 3. This copper sensor is made as a reference to compare the capability of ABS-CB sensor. Then the ABS-CB composite material is 3D printed in the form of thin sheets using FDM process with same width of 50 mm and thickness of 0.4 mm. The capacitance values (C502) for corresponding void fractions
ACCEPTED MANUSCRIPT are measured five times, and the average values are given in table 3. The capacitance values of the copper sensor vary from 5.30 pF – 20.66 pF, but for ABS-CB sensor the capacitance values (C502) vary from 3.66 pF – 6.37 pF. The variation is less when compared to the copper sensor, but the variation in capacitance values is measurable. The variation of capacitance
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value with the change in the void fraction is given in Fig. 6. The capacitance value decrease with increase in the void fraction for the copper sensor (Fig. 6(a)), a similar trend is obtained for the 3D printed ABS-CB sensor (Fig. 6(b)). Hence ABS-CB can be used as a replacement
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for copper for making concave capacitance sensor.
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(a)
(b)
Fig. 6 – Variation of capacitance value with change in void fraction for (a) copper sensor and (b) ABS-CB sensor
ACCEPTED MANUSCRIPT 3.2. Effect of sensor thickness The ABS-CB sensors are 3D printed by varying thickness with constant width and length. The capacitance value increases with an increase in fluid level or decrease in a void fraction. The Figs. 7(a), (b) and (c) shows the effect of sensor thickness on capacitance values
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at different void fractions for a sensor width of 30 mm, 50 mm and 70 mm respectively. The capacitance value increases with an increase in sensor thickness, this is due to the fact that the increase in sensor volume increase the CB content which in turn reduce the resistance values
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and increase the capacitance values.In all the cases minimum capacitance values are obtained for sensor thickness of 0.2 mm and maximum capacitance values are obtained for sensor
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thickness of 0.6 mm.
(b)
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(c)
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Fig. 7 – Effect of sensor thickness on capacitance value for a width of (a) 30 mm, b) 50mm,
3.3. Effect of sensor width
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and (c) 70mm
The ABS-CB sensors are 3D printed by varying width with constant thickness and
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length. The capacitance value increases with an increase in fluid level or decrease in a void fraction. The Figs. 8 a, b and c shows the effect of sensor width on capacitance values obtained at different void fractions for a sensor thickness of 0.2 mm, 0.4 mm and 0.6 mm
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respectively. The capacitance value increases with an increase in sensor width. This is due to the fact that capacitance is directly proportional to the capacitor area. In all the cases
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minimum capacitance values are obtained for a sensor width of 30 mm, and maximum capacitance values are obtained for sensor thickness of 70 mm.
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(a)
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(b)
(c) Fig. 8 - Effect of sensor width on capacitance value for thickness value of (a) 0.2 mm, b) 0.4 mm, and (c) 0.6 mm
ACCEPTED MANUSCRIPT 3.4. Statistical analysis Analysis of variance (ANOVA) is done to find the significant parameter that affects the capacitance value. In this experiment capacitance values are measured for five void
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fraction values (100%, 75%, 50%, 25%, and 0%). The ANOVA is carried out using Minitab statistical software for all the five void fractions. The sensor width (W) with three levels (30 mm, 50mm, 70mm) and sensor thickness (T) with three levels (0.2 mm, 0.4 mm, 0.6 mm) are taken as input parameters, and capacitance value is the output. The capacitance values for
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nine 3D printed sensors are measured for each void fraction as given in Table 3; totally it is
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45 capacitance values for 5 void fractions. The capacitance values of 3D printed sensors for 100% void fraction is given as a response. The ANOVA results for 100% void fraction are given in Table 4. From the F-value and P-value (P-values < 0.05 are significant) it is confirmed that both the width and thickness of the sensor are the significant factor affecting capacitance value. Similarly, the ANOVA is conducted for the other 4 void fractions, and the
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results show that both the sensor width and thickness are the significant factors affecting capacitance values.
Degrees of
Sum of
Mean squares
F- value
P-value
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Source
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Table 4 - Results of ANOVA for 100% void fraction
freedom
squares
Width(W)
2
1.95709
0.978544
470.96
0.000<0.05
Thickness(T)
2
0.22096
0.110478
53.17
0.001<0.05
Error
4
0.00831
0.002078
Total
8
2.18636
ACCEPTED MANUSCRIPT The regression analysis was carried out using Minitab statistical software by keeping the width as constant and varying the thickness and capacitance value to predict the void fraction. The regression equations obtained for 3 sensor widths are given below.
50 mm sensor: V = 286 - 125 T – 52.4 C + 42.0 T*C 70 mm sensor: V = 259 - 39 T – 38.8 C + 17.9 T*C
(3)
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30 mm sensor: V = 249 - 61.1 T – 53.9 C + 35.9 T*C
(4) (5)
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The R2 value obtained for equation 3 (30 mm width) is 97.6% .The maximum
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deviation of 10.95 and minimum deviation of 0.82 is obtained for 30 mm width. The average deviation of the void fraction is 4.26. The R2 values of 95.6% and 92% are obtained for equation 4 and 5 respectively. The maximum, minimum and average deviation in void fraction of 12, 3.19 and 6.92 respectively are obtained for 50 mm by substituting the thickness and capacitance values. Similarly, the maximum, minimum and average deviation
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in void fraction of 18.90, 1.17 and 8.66 respectively are obtained for 70 mm width. The combined regression equation is obtained by entering all the capacitance readings
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corresponding to the sensor width and thickness. The equation 6 gives the combined regression equation.
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V= 246 + 0.39 W - 108 T - 66.6 C + 56.9 T*C + 0.61W*T + 0.364 W*C – 0.489 W*T*C (6) The R2 value obtained for the combined regression equation is 94.8%. The maximum,
minimum and average deviation in void fraction of 17.56, 0.08 and 6.82 respectively are obtained for the combined regression equation. Hence regression equations obtained can be used to predict the void fraction values for different values of width, thickness and capacitance values of 3D printed sensors.
ACCEPTED MANUSCRIPT 4. Conclusions In this paper, the application of the FDM 3D printed ABS-CB concave capacitive sensor in void fraction measurement is reported for the first time and the variation in capacitance values with a change in void fraction (0-100%) are measured and compared with
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the copper sensor. The capacitance values increase with an increase in water level or decrease in a void fraction. The capacitance values obtained for copper (Ccu) ranges from 5.30 pF – 20.66 pF. The variation in capacitance values of 3D printed ABS-CB sensor with 50 mm
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width and 0.4 mm thickness (C502) is very less, i.e. 3.66 – 6.37 pF when compared to the copper sensor, but it is measurable. Also the response time of this sensor is evaluated as 6.9
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seconds. Hence ABS - CB sensor can be used instead of the copper sensor for void fraction measurement of water – air two-phase flow.
The effect of sensor width and thickness on variation in capacitance values is also studied, and it was found that the capacitance value increases with an increase in width and
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thickness. This is due to the fact that the capacitance value is directly proportional to the sensor area. Hence increase in width increases sensor area which in turn will increase the capacitance value. The increase in width and thickness will also increase the CB content
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capacitance value.
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which in turn will decrease the resistance of the sensor. This also leads to an increase in the
The ANOVA results show that both the sensor width and thickness are the significant
factors that affect the capacitance values for all five void fractions (0%, 25%, 50%, 75% and 100%). The regression equations generated can be used to predict the void fraction from the capacitance value measured. Hence a low-cost FDM 3D printed capacitive sensor can be used as a replacement for a copper sensor for measuring the void fraction of air-water two-phase flow.
ACCEPTED MANUSCRIPT Acknowledgment The authors are thankful to Dr. B. Vasuki, Head of the Department, Instrumentation and Control Engineering, National Institute of Technology, Tiruchirappalli, 620015, India for
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Composites Part B: engineering Highlights •
ABS-CB composite is successfully 3D printed in the form of sheets using FDM process
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and it is used as low cost concave capacitive sensor for measuring void fraction of twophase flow. •
The capacitance values obtained for copper (Ccu) ranges from 5.30 pF – 20.66 pF. The
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variation in capacitance values of 3D printed ABS-CB sensor with 50 mm width and 0.4 mm thickness (C502) is very less, i.e. 3.66 – 6.37 pF when compared to the copper sensor,
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but it is measurable.
The effect of sensor width and thickness on variation in capacitance values is also studied, and it was found that the capacitance value increases with an increase in width and thickness.
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The ANOVA results show that both the sensor width and thickness are the significant factors that affect the capacitance values for all five void fractions (0%, 25%, 50%, 75%
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and 100%).
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•