Structural Health Monitoring of Composites Using Integrated and Flexible Piezoelectric Ultrasonic Transducers

Abstract

Two types of ultrasonic sensors are presented for structural health monitoring (SHM) and non-destructive testing (NDT) of graphite/epoxy (Gr/Ep) composites of thickness ranging from 1 mm to 12.7 mm. These piezoelectric film-based sensors are fabricated using a sol-gel spray technique. The center operation frequency of these sensors ranges from 1.3 MHz to 14.5 MHz. For the first sensor type, piezoelectric films of thickness ≥30 μm were deposited directly onto planar and curved Gr/Ep composites surfaces as integrated sensors. Ultrasonic signals propagating in a distance of more than 300 mm have been obtained. Anisotropy of 08 and 908 cross ply Gr/Ep composite is measured and delamination detected. For the second sensor type, piezoelectric films are coated onto a 50 μm thick polyimide membrane as flexible sensors that may be attached to a host composite structure with planar or curved surfaces. An induction type non-contact method for the interrogation of the Gr/Ep composites using integrated sensors is also presented.

Model-based and Signal-Based Inverse Methods

“…Piezoelectric transducers from their conception stage to modern times have been widely used in different types of electronic devices. This fact is due to that these semi structures have a low manufacturing cost and reduced dimensioning, combined with low operational energy consumption that makes them attractive in engineering applications (Kobayashi et al, 2009).…”

“…Previous studies have proven this biologically inspired method capable of successfully performing complex optimizations-see, for instance, Kobayashi et al [2009], Stanford et al [2012], Stanford et al [2012], Kolonay and Kobayashi [2015]. Here we explore a mechanism of cellular division in neurosciences to enhance the search effectiveness and efficiency in discovering and refining of optimized solutions to engineering problems.…”

Low Temperature Adhesive Bonding-Based Fabrication of an Air-Borne Flexible Piezoelectric Micromachined Ultrasonic Transducer

“…Recent advances in flexible electronics provide innovative materials and fabrication processes making it possible to realize flexible ultrasound devices that can be coupled with nonplanar surfaces [9][10][11][12][13][14][15]. For example, piezoelectric nanofibers with excellent properties are one of the types of materials proposed for use in wearable electronics [16][17][18][19], and some sensors can be easily embedded as a part of human skin or clothing for health monitoring by the near field electrospinning (NFES) technique [20][21][22].…”

Remote inspection system for impact damage in large composite structure

“…An inductively coupled transducer system (ICTS) was initially proposed by Greve et al [19,20], and inductive coupling is employed in the current paper to realize the concept shown in figure 1a. The same technique has also been used by Wu et al [21,22] for thorough-thickness inspection with flexible transducers. The proposed ICTS is shown in figure 1b and consists of three coils.…”