Piezoelectric composite sensor

Piezoelectric Composite Sensors. The concept of piezoelectric composites comes from the idea to connect an active piezoelectric phase with a passive matrix phase in a way that the best features from both components can be enhanced and the shortcomings can be minimized correspondingly. Common examples are composites from a stiff ceramic with a soft polymer. 

Tracy M, Chang FK. Identifying impacts in composite plates with piezoelectric strain sensors, part I theory. J Intell Mater Syst Struct 1998 9(11) 920—8. 

Nunes-Pereira, J., Sencadas, V, Correia, V, Rocha, J.G., Lanceros-M ndez, S., 2013. Energy harvesting performance of piezoelectric electrospun polymer fibers and polymer/ceramic composites. Sensors Actuat. A Phys. 196,55-62. 

Shown in Fig. 3.16 is a 1-3 piezoelectric composite with PZT ceramic rods embedded in a polymer resin. This structure is now widely used in medical ultrasonic transducers because the polymer helps reducing the acoustic impedance mismatch between human body and the PZT so that energy transmission becomes more efHcient. The load on the polymer phase can be transferred to the ceramic so that the effective load on the ceramic is enhanced, which produces higher electric signal when it is used as stress sensor. This composite structure also gives a much higher figure of merit for hydrophone applications [18],... 

For a direct integration of the sensor elements in the structure (or at least of an outline compliant apphcation to the structme) piezoelectric composites or polymers (e. g. PVDF) are particularly appropriate. 

Konka, H.R., Wahab, M.A., Lian, K., 2012. The effects of embedded piezoelectric fiber composite sensors on the structural integrity of glass-fiber-epoxy composite laminat. Smart Mater. Struct. 21 (1), 1-9, 015016. 

Zhang et al. [83,84] have shown theoretically that the basic elastic coupling mechanism between the two componeata b the 2>2 piezoelectric composite is similar to that of the 1-3 composite, although the 2-2 structure b not widely us There ate two major areas where 1-3 composites have been widely used underwater hydrophone applications and ultrasonic actuators and sensors for medical dUgnostk devices [15,16,24,8334]. 

Researchers have been exploring a variety of ways in which piezoelectric sensors can be used to help solve such problems. For example, composite fabrics have been developed for use as seat covers in which piezoelectric fibers are embedded in a ground material. The fibers detect the position a person takes on the seat, the person s weight, and any changes the person makes while seated in the car. This information can be used to determine whether an airbag needs to be deployed and, if so, to what pressure it should be inflated. 

Beginning with the work by Ohno and Yonezawa on PFN-PFW systems in the late 1970s [8], many multicomponent dielectric systems have been evaluated and put into manufacture. Some of the patented compositions developed for multilayer capacitor (MLC) application were recently summarized by Shrout and Dougherty [9]. Other compositions were developed for piezoelectric sensors and electrostrictive actuator applications [10]. Most of the compositions used for capacitor dielectrics are based on PFN [8], PMN [11-14], or PZN [15]. 

There are some excellent review articles on different aspects of mesostructured materials, such as synthesis, properties, and applications. " Extensive research effort has been devoted to the exploitation of new phases (lamellar, cubic, hexagonal structures), expansion of the pore sizes (about 2-50 nm are accessible), and variable framework compositions (from pure silica, through mixed metal oxides to purely metal oxide-based frameworks, and inorganic-organic hybrid mesostructures). Another research focus is on the formation of mesostructured materials in other morphologies than powders, e.g. monolithic materials and films, which are required for a variety of applications including, but not limited to, sensors (based on piezoelectric mass balances or surface acoustic wave devices), catalyst supports, (size- and shape-selective) filtration membranes or (opto)electronic devices. The current article is focused... 

Figure 16.6 Piezoelectric wafer active sensors (PWAS) installation, (a) 7 mm PWAS on a metallic structure (b) 7 mm round and square PWAS on a composite structure.

Giurgiutiu V, Harries K, Petrou M, Bost J, Quattlehaum JB. Disbond detection with piezoelectric wafer active sensors in RC structures strengthened with FRP composite overlays. Earthq Eng Eng Vib 2003 2(2) 213—24. 

On the other side, integrity monitoring techniques must be used to get more information on the state of the damage in the stracture. Piezoelectric sensors and optical fibers have been used for health monitoring of polymer composites, however their use is rather expensive. 

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