calibration of impact localization of a passive smart...

Calibration of Impact localization of a Passive Smart Composite Plate

Fabricated by Embedded PZT Patch

MMS DEZFOULI1, MOHD HAFIDZ RUSLAN

1, MOHAMMAD KARAMI

2, K SOPIAN

1, B

BAKHTYAR1

1Solar Energy Research Institute (SERI), National University of Malaysia

43600 UKM Bangi, Selangor,

Malaysia 2Department of Mechanical Engineering, University of Malaya, 50603,

Kuala Lumpur, Malaysia

Email: [email protected]; [email protected]

Abstract: - Passive smart composite is consisted of host composite structure and embedded piezoelectric

sensor. In this paper, passive smart composite plate is a structure including sensors and fabricated which is

included one PZT (Lead Zirconate Titanate or piezoelectric ceramic material) patches that is cheaper than PZT

wafer. In order to avoid decoupling of the PZT patch and wire spoiling, the composite plate fabricated in low

temperature using hand lay-up method. For identifying impact location using one sensor, output voltages of the

sensor were analyzed by comparing experimental and theoretical results. This paper poses that by increasing

the distance of impact point from PZT sensor, value of out put voltage decreased. Also, the locus of the impact

point was identified by output voltage.

Key-Words: - Passive smart composite, Piezoelectric, Embedded piezoelectric, PZT patch,

1 Introduction Structural health monitoring systems have

developed in varieties of applications in recent

years. There are many researches and studies on

different aspects of smart structure systems made

by physicist and engineers in fields of aerospace,

mechanical and civil engineering [1]. The smart

structure system is constituted by both host

structure includes a laminate composite beam and

the sensing elements (actuations) include

piezoceramic patches [2]. Widespread development

in the researches and the studies is due to the

importance and varieties of applications of the

system in different engineering sciences such as

aircraft wing, submarine sterns, vibration control

and etc [3].

One of the most important applications of the

systems is to evaluate the structures of composite in

terms of impact damage and Acoustic Emission

(AE) which has been applied for damage detection

[4, 5]. Many researchers have evaluated acoustic

wave propagation and damage detection by

embedding or bonding PZT (Lead Zirconate

Titanate or piezoelectric ceramic material)

sensors/actuators in the composite structure.

Generally, studies in field of damage detection

regarding how to use the PZT sensors/actuators can

be divided to active and piezocomposite categories

[6].

Active systems use sensor to detect damage

and actuator in which actuator receives an input

voltage and actuates structure of composite plate

and resulted acoustic wave is propagated in the

composite. PZT sensor shows output signal after

receiving Acoustic Emission (AE) wave. In case of

damage in the composite structure, the output

signal of PZT signal is changed. The changes of the

signal is evaluated and analysed by comparing

signal wave before and after the damage [7, 8].

Passive systems only use PZT sensor as the AE

created by impact is propagated through structure

of the composite; damage detection is analysed

after receiving AE wave by PZT sensor [9].

Monitoring of impact damages in composite

laminate was used to evaluate the output acoustic

wave by Guan and Yong [10]. They proved that AE

wave caused by impact includes important

information that describes composite structure

regarding to availability or unavailability of the

damage. Evaluating the impact behaviour of the

composite laminate in order to detecting the

structural properties of the composite is a very

complicated task so that different analysis methods

have been employed by many researchers. Sung et

Recent Advances in Automatic Control, Modelling and Simulation

ISBN: 978-1-61804-177-7 34

al.[11] analysed output signal on the time-

frequency domains using wavelet transform (WT)

method and impact monitoring on a composite

laminate including a bonded PZT sensor. In this

method, the characteristics of the AE waves, made

by impact, have been analysed in the passive

sending diagnosis (PSD) system on time-frequency

domains. Red et al. Evaluated damage detection by

expressing WT as a signal process technique that

includes Fourier transforms. Su et al [14] evaluated

a damage identification system, which includes a

bonded PZT on a composite bead, and their

analysis was based on the acoustic wave

propagated by impact damage.

Diamanti et al.[12] successfully detected the

impact damage on a Carbon-fibre-reinforce plastic

(CFRP) laminate by using a PZT patch which was

attached on the composite surface. They detected

impact damage by investigating propagation of

lamb wave and using Finite element analysis.

Ghoshal et al.[13] evaluated damage detection

based on stress wave parameters by simulating

acoustic wave propagation on a Quasi- isotropic

glass-epoxy plate including a bonded PZT patch

based. According to previous studies discussed

above, PZT patch has been bonded on the

composite plate and embedded piezoelectric

materials, which have been used in the previous

studies, were other kinds of piezoelectric material

such as wafer that are more expensive than PZT

patch. Therefore, in this manuscript a piezo-

composite plate has been fabricated including four

fibreglass layers with one embedded PZT patch

through its two intermediate layers using cut-out

method. This paper also, presents a study on

investigation of output voltage from PZT patch by

impact force on the piezo-composite.

2 Material and Methods There are three methods for inserting PZT patch

through composite layers:

1- Smart layer

2- Inserting without cut-cut

3- Cut-out method

Previous studies regarding embedding

piezoelectric materials were mainly focused on the

application of PZT wafer using the cut-out method

and also the application of PZT element using the

smart layer method. Accordingly and with the

approach of presenting a cost effective design,

current study employed a PZT patch for embedding

in composite layers based on cut-out method. The

cut-out method used in this study for fabricating

smart plate and composite materials includes PZT

patches, fiberglass rowing and epoxy.

Piezoelectric materials are PZT patch PIC155- PI

Ceramic GmbH (from Germany) that like a circular

disc with 1mm thickness and 10mm diameter. It

has a grey line like an incomplete circular that

separates the positive pole (+) of sensor from the

negative pole (–). The internal of grey circular has

a positive pole and the external of it and the sheet

behind the sensor have the negative pole. The

fibreglass was E-glass fibre woven roving (04

XINGDA- DIY Trade- from China) that each of its

layers had 0.25mm thickness. The epoxy resin was

Epoxy BBT 7892 (Berjaya Bintang Timur Sdn.

Bhd Malaysia). Epoxy BBT-7892 is two-

component liquid epoxy system, which is specially

designed for wet lay-up laminating process in

composite application. It provides good wetting to

most of composite materials. Detail of properties of

BBT-7892 is shown in Table 1.

Table 1. Mechanical Properties of Epoxy BBT

7892

The process of fabricating composite plate

with embedded PZT patch is divided to five steps

including (i) preparing mould and epoxy resin, (ii)

cut-out fiberglass, (iii) soldering PZT sensor to

wire, (iv) embedding PZT sensor into layers, (v)

drying up the composite plate.

One symmetric point in the middle layers of

the composite plate were cut-out with the same size

as PZT sensors purposely for embedding the

sensors in the composite plate. The plastic sheet

holder of the first composite layer was placed on

the mould. Next, the second and third layers (cut-

out layers) were placed on the first layer in which

the fibers of second and third layers made angel of

45o with fibers of the first layer (Figure 1).


ISBN: 978-1-61804-177-7 35

Fig. 1. Schematic of piezo-composite

3 Experimental setup As shown in the Figure 2, if an impact happens on

the point A of the composite with PZT Patch, a

stress is produced. This stress is propagated in form

of mechanical wave through the composite plate

and reaches point B near the PZT patch.

Fig. 2. Propagation stress wave from impact point

(A) to sensor (B)

If the pressure on point A and B are equal to

PA and PB, respectively, PB is less than P

This relation is proven by the analysis of the

deformation of an element in one

stress (equation 1) [14]:

x

cp bB

∆

⋅=σ

where PB is the pressure at point B, which has

distance of ∆x from impact point (A), σ is stress

because of pressure PA in impact point, ∆x is the

distance of between point A to point B.

Equation of normal stress is (equation

A

F=σ

Where F is impact force (N), and A is area of cross

section of the rod (m2), Substitution of (

yields (equation 3)

Ax

cFp b

B⋅∆

⋅=

composite structure

, if an impact happens on

composite with PZT Patch, a

stress is produced. This stress is propagated in form

of mechanical wave through the composite plate

and reaches point B near the PZT patch.

Propagation stress wave from impact point

on point A and B are equal to

is less than PA (PB<PA).

This relation is proven by the analysis of the

ment in one- dimensional

is the pressure at point B, which has

distance of ∆x from impact point (A), σ is stress

because of pressure PA in impact point, ∆x is the

distance of between point A to point B.

equation 2)[15]:

Where F is impact force (N), and A is area of cross

), Substitution of (2) into (1)

In this study A= 19.625 x 10

1.62. The Equation (2) shows the pressure at point

B has inverse relationship with distance of impact

point from the sensor, which means by increasing

the distance of impact point (∆x), pressure value

decreases. Hence, PB is less than PA.

The values of the pressure on the sensors

caused by the impacts were calculated by

substituting the output voltages in the

[16]:

Where is the dielectric constant,

piezoelectric constant, D is the diameter of PZT

sensor, h is the thickness of PZT sensor, P is the

pressure, V is the output voltage, and

Poisson ratio. In this study,

F/m,

(m), and

4 Experimental procedure Figure 3, shows experimental

piezo-composite plate. The model of oscilloscope

is TEKTRONIX - TDS2012B with 100MHz

Bandwidth, 1.0 GS/s Sample rate, and two

channels. Data were collected while the

oscilloscope voltage selector set on 10mV/div. The

sensitivity of TEKTRONIX

2mV/div. The impact tests were done on the floor

in fixed conditions. By doing impact test on three

circles with radii of 2, 4 and 6 (cm) (C1 with radii 2

cm, C2 with radii 4 cm, and C3 with 6 cm) which

their centre was the sensor, the relationship

between force and pressure on the sensor was

evaluated. By changing the releasing height of the

rod from the composite plate (h1=1, 2, …7 cm)

seven forces was put on the three points with 2, 4

and 6 (cm) distance from the sensor.

Fig. 3. Experimental tests with different fo

in different points on the composite plate

( )V

D

h

dP

υ

ε

−=

1

1

3

162

31

33

33ε

10

31 1065.1 −×−=d

01.0=D .0=υ

In this study A= 19.625 x 10-6, and ,Cb is

) shows the pressure at point

B has inverse relationship with distance of impact

point from the sensor, which means by increasing

of impact point (∆x), pressure value

decreases. Hence, PB is less than PA.

The values of the pressure on the sensors

caused by the impacts were calculated by

substituting the output voltages in the (equation 4)

is the dielectric constant, is the

piezoelectric constant, D is the diameter of PZT

sensor, h is the thickness of PZT sensor, P is the

pressure, V is the output voltage, and is the

Poisson ratio. In this study,

(m/V), (m),

.

Experimental procedure hows experimental procedure on the

plate. The model of oscilloscope

TDS2012B with 100MHz

Bandwidth, 1.0 GS/s Sample rate, and two

channels. Data were collected while the

oscilloscope voltage selector set on 10mV/div. The

sensitivity of TEKTRONIX - TDS2012B is

pact tests were done on the floor

doing impact test on three

circles with radii of 2, 4 and 6 (cm) (C1 with radii 2

cm, C2 with radii 4 cm, and C3 with 6 cm) which

their centre was the sensor, the relationship

sure on the sensor was

evaluated. By changing the releasing height of the

rod from the composite plate (h1=1, 2, …7 cm)

seven forces was put on the three points with 2, 4

and 6 (cm) distance from the sensor.

Experimental tests with different force value

in different points on the composite plate.

31d

υ9

33 10124.2 −×=ε

10

001.0=h

3.


ISBN: 978-1-61804-177-7 36

Each force on each point caused an output

voltage from sensor and therefore there were seven

output voltages from each point.

figure 4 the impact on the composite plate is

produced by releasing rod from height (h) on

composite plat.

Fig. 4. Releasing rod on the composite plate

Table 2. shows force and pressure values at

impact point by changing the releasing height of

the rod from the composite plate.

Table 2. Force and pressure values at impact point

5 Results and Discussion As shown in Figure 5, by doing the impact test and

getting far from PZT sensor the domain of the first

packet of wave decreased. The first packet of wave

in distance of 20mm from PZT sensor was

maximum and the first packet of wave in distance

of 60mm from PZT sensor was minimum.

Therefore, by increasing the distance of impact

point from PZT sensor, the domain of the first

packet of wave (PK-PK) and the external voltage

decreased. The reason of this state will be

Each force on each point caused an output

voltage from sensor and therefore there were seven

output voltages from each point. According to

figure 4 the impact on the composite plate is

asing rod from height (h) on

Releasing rod on the composite plate

shows force and pressure values at

impact point by changing the releasing height of

at impact point

As shown in Figure 5, by doing the impact test and

getting far from PZT sensor the domain of the first

packet of wave decreased. The first packet of wave

in distance of 20mm from PZT sensor was

first packet of wave in distance

of 60mm from PZT sensor was minimum.

Therefore, by increasing the distance of impact

point from PZT sensor, the domain of the first

PK) and the external voltage

The reason of this state will be

demonstrate by comparing theoretical and

experimental results in below.

Fig. 5. The first packet of wave

PZT sensor

Figure 6. shows impact forces versus pressures

on the PZT sensor (experimental results and

theoretical results) in which the horizontal axis is

the force value for impact and vertical axis is the

pressure on the PZT sensor. C1, C2, and C3 are the

names of three circles with radiuses 2, 4, and 6

(cm) from PZT sensor. On each line, there is 7

points which means 7 force values were impacted

on each circle (2, 4, and 6 cm from PZT sensor).

The results of experimental and theoretical impact

on the 7 points on each circle

lines (one line for experimental result and one line

for theoretical result). There are 3 lines for

experimental result and 3 lines for theoretical result

which each line indicates relationship between

pressure on the sensor and forc

2, 4 and 6 (cm) distances from the sensor.

The theoretical results were achieved by

mentioned equations and force values in table

These lines have an increasing trend that means by

increasing impact force value

the composite plate, the pressure on the sensor

increases.

Fig. 6. Experimental and theoretical result of

pressure on the sensor versus

by comparing theoretical and

experimental results in below.

The first packet of wave output voltage from

PZT sensor

shows impact forces versus pressures

on the PZT sensor (experimental results and

theoretical results) in which the horizontal axis is

the force value for impact and vertical axis is the

pressure on the PZT sensor. C1, C2, and C3 are the

cles with radiuses 2, 4, and 6

On each line, there is 7

points which means 7 force values were impacted

on each circle (2, 4, and 6 cm from PZT sensor).

The results of experimental and theoretical impact

on the 7 points on each circle (C), are shown as two

lines (one line for experimental result and one line

for theoretical result). There are 3 lines for

experimental result and 3 lines for theoretical result

which each line indicates relationship between

pressure on the sensor and forces on the points with

from the sensor.

The theoretical results were achieved by

and force values in table 2.

These lines have an increasing trend that means by

force value on different points of

the composite plate, the pressure on the sensor

Experimental and theoretical result of

pressure on the sensor versus impact force values.


ISBN: 978-1-61804-177-7 37

Hence, it can be resulted that pressure on the

sensor has direct relation with force cause

impact.

The difference between lines C1 experimental

and C2 experimental is larger than the difference

between lines C2 experimental and C3

experimental that means when the impact point

recedes the sensor (supposing the force is constant)

the pressure on the sensor decreases and the ratio of

reduction of the pressure decreases. Therefore, the

pressure on the sensor has indirect relation with

distance of impact point from the sensor.

comparing experimental and theoretical result, a

few points can be mentioned which are explained

in below.

By increasing impact force value, difference

between lines C1 theoretical, and C1 experimental

will increase, it means by increasing impact force

value in distance of 2 cm from PZT sensor, the

difference of experimental and theoretical result of

pressure on the sensor will increase.

impact force value, difference of lines C2

theoretical and C2 experimental will increase,

which means by increasing impact force value in

distance of 4 cm from PZT sensor, th

experimental and theoretical result of pressure on

the sensor will increase. The lines of C3 theoretical

and C3 experimental were almost close to each

other, which means by increasing impact force

value in distance of 6 cm from PZT sensor,


the sensor is almost the same. Therefore, by

increasing distance of impact point from PZT

sensor the difference of experimental and

theoretical result will decrease, because by


sensor, sensitivity of PZT sensor will decreases.

Fig. 7. Output voltages from PZT sensor versus

pressure on sensor

Since the pressures on the sensor caused

output voltages from the sensor, output voltages

Hence, it can be resulted that pressure on the

sensor has direct relation with force caused by

The difference between lines C1 experimental

and C2 experimental is larger than the difference

between lines C2 experimental and C3

experimental that means when the impact point

recedes the sensor (supposing the force is constant)

on the sensor decreases and the ratio of

reduction of the pressure decreases. Therefore, the

pressure on the sensor has indirect relation with

distance of impact point from the sensor. By

comparing experimental and theoretical result, a

mentioned which are explained

By increasing impact force value, difference

between lines C1 theoretical, and C1 experimental

will increase, it means by increasing impact force

value in distance of 2 cm from PZT sensor, the

tal and theoretical result of

By increasing

impact force value, difference of lines C2

theoretical and C2 experimental will increase,

which means by increasing impact force value in

distance of 4 cm from PZT sensor, the difference of


The lines of C3 theoretical

and C3 experimental were almost close to each

other, which means by increasing impact force

value in distance of 6 cm from PZT sensor,


Therefore, by


sensor the difference of experimental and

theoretical result will decrease, because by

t point from PZT

sensor, sensitivity of PZT sensor will decreases.

Output voltages from PZT sensor versus

Since the pressures on the sensor caused

output voltages from the sensor, output voltages

from the sensors versus the pressure on the sensor

were evaluated by using equation

horizontal axis is pressure on the sensor and the

vertical axis is the output voltage. The lines have

increasing trend that means by increasing the

pressure on the sensor the output voltage increases.

The calibration constant is 980.78, which means

VP ×= 78.980 .

Therefore, pressure has direct relation with

voltage. The line R2 is below the line R1 and the

line R3 is below the line R2 that means wh

impact points recedes the sensor, the pressure on

the sensor and the output voltage decreases.

Therefore, the output voltage has an indirect

relationship with the distance of impact point from

sensor.

As shown in figure 8

impact on the composite plate with a PZT Patch, if

impact happens on the random points of the

composite, the locus of the impact point can be

identified by output voltage. The locus of the

impact was a circle that R was radius, sensor was

the center, and R was obtained from equation

R= 0.104 V + 10.01,

Where V is the output voltage from PZT sensor.

Fig. 8. The locus of the impact point on

composite plate with a PZT sensor

6 Conclusions This paper presents experimental

investigation of Impact localization

composite plate. A PZT patch was embedded inside

the four composite layers using cut

hitting impact on the fabricated composite plate

with embedded PZT patch, signal from the

embedded PZT patch was detected.

by increasing the distance of impact point from

PZT sensor, value of external voltage decreased.

Therefore, if impact happens on the random points

from the sensors versus the pressure on the sensor

using equation 4 In figure 7, the

horizontal axis is pressure on the sensor and the

vertical axis is the output voltage. The lines have

increasing trend that means by increasing the

ure on the sensor the output voltage increases.

The calibration constant is 980.78, which means

Therefore, pressure has direct relation with

voltage. The line R2 is below the line R1 and the

line R3 is below the line R2 that means when

impact points recedes the sensor, the pressure on

the sensor and the output voltage decreases.

Therefore, the output voltage has an indirect

relationship with the distance of impact point from

8, to determine location of

t on the composite plate with a PZT Patch, if

impact happens on the random points of the

composite, the locus of the impact point can be

identified by output voltage. The locus of the


obtained from equation (5):

V is the output voltage from PZT sensor.

locus of the impact point on piezo-

plate with a PZT sensor

experimental and theoretical

Impact localization on piezo-

PZT patch was embedded inside

the four composite layers using cut-out method. By

hitting impact on the fabricated composite plate

d PZT patch, signal from the

embedded PZT patch was detected. It found that, ,

by increasing the distance of impact point from

external voltage decreased.

if impact happens on the random points


ISBN: 978-1-61804-177-7 38

of the composite, the locus of the impact point can

be identified by output voltage. The locus of the


the center.

Acknowledgements The authors would like to thank the Solar Energy

Research Institute (SERI), University Kebangsaan

Malaysia for providing the laboratory facilities and

technical support.

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ISBN: 978-1-61804-177-7 39

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