Dispersed Sensing Networks in Nano-Engineered Polymer Composites: From Static Strain Measurement to Ultrasonic Wave Acquisition

Abstract

Self-sensing capability of composite materials has been the core of intensive research over the years and particularly boosted up by the recent quantum leap in nanotechnology. The capacity of most existing self-sensing approaches is restricted to static strains or low-frequency structural vibration. In this study, a new breed of functionalized epoxy-based composites is developed and fabricated, with a graphene nanoparticle-enriched, dispersed sensing network, whereby to self-perceive broadband elastic disturbance from static strains, through low-frequency vibration to guided waves in an ultrasonic regime. Owing to the dispersed and networked sensing capability, signals can be captured at any desired part of the composites. Experimental validation has demonstrated that the functionalized composites can self-sense strains, outperforming conventional metal foil strain sensors with a significantly enhanced gauge factor and a much broader response bandwidth. Precise and fast self-response of the composites to broadband ultrasonic signals (up to 440 kHz) has revealed that the composite structure itself can serve as ultrasound sensors, comparable to piezoceramic sensors in performance, whereas avoiding the use of bulky cables and wires as used in a piezoceramic sensor network. This study has spotlighted promising potentials of the developed approach to functionalize conventional composites with a self-sensing capability of high-sensitivity yet minimized intrusion to original structures.

Acousto-ultrasonics-based health monitoring for nano-engineered composites using a dispersive graphene-networked sensing system

“…However, 180 kHz and S 0 wave mode were selected for diagnostic wave signals, based on the previous frequency sweep test. 29 Figure 14(a) shows the amplitudes of captured wave signals at multiple frequencies, in which the peak value appears at around 180 kHz for the S 0 mode, similar to the trend of the signals captured by a PZT sensor. Such a phenomenon – the frequency-dependent signal amplitude – is mainly caused by wave mode tuning of PZT actuators.…”

“…For as-produced laminates in this study, the elastic tensile modulus and ultimate tensile strength have been improved by 35% and 8%, respectively. 29 In conclusion, these appealing features have blazed a new trail in developing dispersive sensing systems for SHM. The sensors can flexibly adapt to a curved surface, introduce ignorable weight/volume penalty to host materials, and be networked in a dense modality to provide rich information of the structural health status.…”

“…However, 1.0 wt% graphene was dispersed into epoxy resin as the optimal quantity before application on fabrics. 29 The mixture was initially mechanically stirred while being heated to 80 °C and then treated in an ultrasonic bath to obtain a homogeneous mixture (Figure 1). Each glass fibre layer was impregnated with graphene-enriched epoxy using a hand roller (Figure 2(a)).…”

“…According to our previous study, a pair of electrodes on the surface of the composite plate thus made can extract the local response of Lamb waves propagating in the plate structure through the dispersive graphene-formed network (GN). 29 Instant impact will create an acoustic source which emits elastic waves along the structure. These acoustic emission (AE) signals carrying source information are captured by GN and recorded at different sensing locations.…”

A Spray-on, Nanocomposite-Based Sensor Network for in-Situ Active Structural Health Monitoring

“…Targeting characterization of damage, ToAs of the damage scattered wave and the directly incipient wave recorded via the same sensing path PZT 1 - Sen 1 are used to calculate the ToF, as seen in Figure 9c. A probability-based diagnostic imaging (PDI) algorithm [5,6,40], in conjunction with the ToFs obtained from all sensing paths, is then recalled, whereby the damage is characterized in a grayscale image in terms of the probability of presence.…”