Sensors and Actuators A 149 (2009) 233240
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Sensors and Actuators A: Physical
journa l homepage: www.e lsev ier .co
Osama J.a Mechanical Eb Design & Prodc Mechanical E 2, Uni
a r t i c l
Article history:Received 4 FebReceived in reAccepted 28 OAvailable onlin
Keywords:Functional paiCarbon black nConducting poVibration & noise monitoringStructural health monitoring
ionalmakeerstasis inmetenanoo preed tctrossens
to validate the piezoresistance model. Finally, the predictions of the electromechanical model areexperimentally veried by examining the dynamic response of the sensor system under cyclic load-
Paints arproviding psesses a senRecently, sesmart painthealth monpaints are cFor exampletric powderof electrodethe sensingtion processexpensive coutput signsensitive sma repeatablspheric oxy
(W.N. Akl), baz
0924-4247/$ doi:10.1016/j.sing.The ultimate goal of this study is to demonstrate the feasibility of the proposed nanocomposite
functional paint as a sensor for monitoring the vibration, acoustics, and health of basic structural sys-tems.
2008 Elsevier B.V. All rights reserved.
e commonly applied as lms on structures surfaces forrotective and decorative functions.When the paint pos-sing capability, the paint becomes functional or smart.veral attempts have resulted in the development ofs which can be used as sensors for vibration, noise, anditoring applications. The currently available functionalomplex and very expensive for practical applications., smart composite paints which are made of piezoelec-immersed in epoxy resin must be coated with layerss and then poled using very high voltage to impartcapability to the paint . Such a complex prepara-esmake this type of paint very expensive. Furthermore,harge ampliers are needed to monitor the capacitiveals of the smart paint sensor. Alternatively, the pressureart paints which modulate the light intensity through
e chemical interaction of the sensing layer with atmo-gen require the use of an expensive photo-detector such
ding author. Tel.: +966 1 4670166.resses: email@example.com (O.J. Aldraihem), firstname.lastname@example.org@eng.umd.edu (A.M. Baz).
as a CCD camera or photomultiplier tube for interrogation of thepaint .
Carbon black (CB) composite is another class of functionalmate-rial that nds wide applications, e.g., in deformation sensing. Thecomposite consists basically of electrically conductive CB aggre-gates embedded in a polymer matrix. The composite conductivitynoticeably changes with the applied mechanical deformation.
Extensive research effort has been put forth to studying the per-colation theory which is often used to describe the relationshipbetween CB contents and the direct current (DC) conductivity .However, investigation of the sensing ability of CB composites isfocused on the detection of quasi-static effect. For example, thework of Shevchenko et al.  focused on graphite lled polypropy-lene composites, which possess smart properties, such as a positivetemperature coefcient of resistance and strain dependent conduc-tivity. Along a similar direction, Kimura et al.  experimentallyillustrated the linear relationship between the logarithms of theresistance and elongation. Furthermore, they developed a modelbased on the tunneling junction model. Flandin et al.  evaluatedthe DC electrical and mechanical properties of composites com-posed of conductive llers impeded into elastomermatrices. Zhanget al.  presented a systematic work on the piezoresistance effectsof electrically conducting compositeswhich are subject to uni-axialpressure. The investigation experimentally veried the theoretical
see front matter 2008 Elsevier B.V. All rights reserved.na.2008.10.017mposite functional paint sensor for vib
Aldraihema,, Wael N. Aklb, Amr M. Bazc
ngineering, King Saud University, PO Box 800, Riyadh 11421, Saudi Arabiauction Engineering Department, Ain Shams University, Cairo, Egypt
ngineering Department, University of Maryland, 2137 Eng. Bldg., College Park, MD 2074
e i n f o
ruary 2008vised form 20 October 2008ctober 2008e 27 November 2008
a b s t r a c t
A new class of nanocomposite functwith carbon black nanoparticles tohensive analysis is presented to undthis class of paint sensors. The analythe sensor system as a lumped-paralized to model the behavior of thea simple amplier circuit in order tsor. Several experiments are performsensor system. First, impedance speColeCole models and to obtain them/locate /sna
ion and noise monitoring
paint sensor is proposed, whereby an epoxy resin is mixedthe sensor sensitive to mechanical excitations. A compre-nd the underlying phenomena governing the operation ofcludes developing an electromechanical model which treatsr system. The Debye and the ColeCole equations are uti-composite paint. The sensor equations are integrated withdict the current and voltage developed by the paint sen-o assess the validity of the proposed models of the paintcopy is employed to verify the validity of the Debye andor electrical parameters. Then, experiments are carried out
234 O.J. Aldraihem et al. / Sensors and Actuators A 149 (2009) 233240
model for the piezoresistance. In another work, Zhang et al. extended their former investigation to study the time dependenceof the piezoresistance. Knite et al.  proposed the use of car-bon black nanocomposites as tensile strain and pressures sensor.The investigmodel baseal.  studimpedanceposed for thgroup of inof graphitefocused onber compo
In this wepoxy resinact as a funcapable offrequency oused to meaby the pain
It is alsoeasily applicontinuoussurfaces. Thcations ranglaunching vcritical stru
In the prmodel of thmonitoringobtain the ptions are ppaint sensoemployed todevelopedthe impeda
Thepaperizes the liteof the functequations. Tobtained frmodel is deprinciple. Ttion whichsystem. Theple electricand voltagepresents exoped modeperformancsummarizepresent stu
2. Model d
The propin Fig. 1, whmake it elec
The geofrom nanosis assumed
To facilithe sensorgates consi
Fig. 1. Sample of a paint sensor.
med to form a continuum phase of a spherical shape. More-ach Cctivitmedprinsch
reme. A vothe ssticrenttionates tat cacem
paincanf thewithd-paingelempertmpise tFurtanducersacouhatused
Fig. 2. Schematic circuit of the sensor.ation included experimental results and a theoreticald on that of Zhang et al. . In a recent work, Wang etied the conduction mechanism in CB composites usingspectroscopy. Three equivalent-circuit models are pro-e various regions of percolation theory curve. Another
vestigators [13,14] studied the piezoresistive behaviorscomposites under static pressures. Das et al.  isthe variation of the resistivity of CB and short carbonsites with the degree of strain at constant strain rate.ork, a nanocomposite paint is proposed whereby anis mixed with carbon black nanoparticles to make it
ctional composite. The paint sensor is very simple andmonitoring vibration and noise down to a quasi-staticf 0Hz. Accordingly, simple electrical circuits can besure the changes in the current and voltage developedt sensor.important to mention that the proposed paint can beed to structures of complex shapes and can act as aly distributed sensor over very large areas of structurale proposed paint sensor can be used in numerous appli-ing frommonitoring infrastructures, payload fairings ofehicles, exible space structures, as well as many otherctures that are only limited by our imagination.esent study, the objective is to develop a comprehensivee paint sensor system for vibration, noise, and healthapplications. A lumped-parameter approach is used toaint sensor equations. Furthermore, impedance equa-
resented to estimate the electrical parameters of ther. Hamiltons principle for electromechanical systems isderive thedynamicequationsof the sensor system.The
models are veried experimentally by examination ofnce spectrum, piezoresistance, and dynamic response.r is organized in four sections. Section 1 briey summa-rature review. In Section 2, the equivalent circuitmodelional paint is developed using the Debye and ColeColehen, estimates of the paint electrical components areom the impedance equations. An electromechanicalrived for the paint sensor system using the Hamiltonshe model is based on an equivalent circuit representa-treats the real sensor system as a lumped-parametersensor system equations are integrated with a sim-
al circuit to enable the measurement of the currentdeveloped by the functional paint sensor. Section 3
perimental validations of the predictions of the devel-ls and provides assessments of the static and dynamice characteristics of the paint sensor system. Section 4s the major conclusions and recommendations of thedy.
rticle paint sensor
osed paint sensor is a conductive composite, as shownereby a polymer resin is mixed with CB aggregates totrically conducting and functional.metric scale of the aggregate can, in general, rangecale to microscale. Furthermore, the composite sensorto be homogeneous on the macroscale.tate modeling formulation, the real microstructure ofis simplied as illustrated in Fig. 2. The primary aggre-st of many CB nanoparticles, where each CB aggregate
is assuover, econduis assu
Theing themeasusensorto biasor acouthecurproporillustratem th(displa
Thewhichtions oalonglumpegovernwhosecal proand dathe sentation.modeltransdelectro
In wwill beB aggregate possesses high-structure of high