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- ItemDevelopment of the fabrication process and characterization of piezoelectric BaTiO3/epoxy composite used for coated ultrasonic transducer patterns in structural health monitoring(Cambridge : arXiv, 2016) Bareiro Ferreira, Oscar; Sridaran Venkat, Ramanan; Adam, Jens; Boller, ChristianStructural health monitoring (SHM) is based on integrating and/or adapting a sensor system into a structure such that a tolerable damage to occur can be monitored. This requires a network of transducers specifically when this SHM approach is considered as a monitoring system such as based on guided waves. A desirable solution would be to get a transducer network simply āprintedā on the structure considered once the network has been designed such as through a simulation approach. In the paper proposed the fabrication process and characterization of a piezoelectric composite to be used as an ultrasonic transducer for damage sensing of structures based on SHM using guided waves is first considered. The composite consists of piezoelectric BaTiO3 particles homogenously distributed in an epoxy resin matrix. A paste with a solid volume fraction of up to 50 vol% was prepared by the direct mechanical mixing of the piezoelectric particles in the epoxy matrix. Due to the ferroelectric properties of BaTiO3 the polarization of the composite is required with a high electric field prior to use. Two electrodes placed on both sides of the samples are required to measure the dielectric and electromechanical properties of the composite in the form of a thick film. The influence of the volume fraction of BaTiO3 on the dialectic properties and piezoelectric transversal constant (d33) of the piezoelectric composite will be shown. Beyond this more materials processing related work performance of those transducers will be demonstrated. This will be done in terms of getting those coated as a transducer pattern/network on a hosting structure after having had the transducer network determined through simulation. Validation of the approach will be done by looking at the transducer networkās performance in terms of detecting guided acoustic waves.
- ItemSensor placement technique using BaTiO3/epoxy resin piezoelectric composite sensors based on differential imaging method for damage detection in structural health monitoring(Cambridge : arXiv, 2016) Taltavull Cazcarra, AdriĆ ; Bareiro Ferreira, Oscar; Sridaran Venkat, Ramanan; Adam, Jens; Boller, ChristianStructural Health Monitoring (SHM) is an emerging technology in many engineering disciplines that aims at designing systems being able to continuously monitor ageing of structures throughout their life span. Damage monitoring using guided waves (GWs) is one promising approach in that regard. Principally a network of integrated piezoelectric transducer patches (actuators and sensors) on a structure generates GWs, where the GWs propagate through the structure and relative information about the damage is finally obtained. Based on damage mechanics principles and damage tolerance criteria, the structureās remaining useful life is then be determined from the data recorded by the transducers and the need for structural maintenance actions can finally be derived accordingly. The detectability of the growing structural damage is highly dependent on the placement of actuators and sensors. This therefore requires an optimum placement of those transducers to be found, which is obtained through simulation. This need for simulation becomes specifically relevant when structures are large and complex. A new approach presented within the paper proposed has therefore been developed, which is based on differential imaging/signals, where the differential is determined from the difference of the wave patterns between an undamaged and a damaged condition. The resulting topology of the differential signal is considered to define the shape/pattern of the respective piezoelectric transducers, which will be placed on the structural component considered using a defined coating process. The coating and monitoring process applied using a BaTiO3/epoxy resin will be demonstrated on a thin aluminium test coupon with three holes where a crack of tolerable length has originated from one of the holes due to fatigue loading and the coated piezoelectric composite transducer pattern for monitoring the crack has been defined from the output of guided wave FEM simulations.