Historically, the development of strain sensing elements has proven critical to the study of structural engineering concepts and designs. Traditional foil strain gauges have granted engineers the ability to develop more efficient load-bearing designs while being inherently simple to apply and observe via electrical interrogations. Recently, there has been a growing interest in the use of such sensing technology for structural health monitoring (SHM) due to the advances of piezoresistive strain sensors of various types. Specifically, conductive polymer composites (CPC) have been of great interest to the SHM research community over the past few years. CPCs show great potential for SHM due to the simplicity of their measurement, the unobtrusiveness of their design, and homogeneity achievable by the components used in their manufacture for deployment in fiber-reinforced polymer composites. In addition to the aforementioned attributes, researchers have also identified CPC compositions that produce sensors with strain sensitivities greater than that of traditional foil gauges. Recent studies have shown that generally sensors of this form experience a drift in their nominal output as they are subjected to fatigue and other forms of damage accumulation. In this research, such phenomena are recreated and explored through the development of a spray-layer-by-layer (sLBL) manufacturing apparatus and the exploration of produced carbon black based CPC films. The relationship between sLBL parameters (e.g. stage speed, air pressure, mixture viscosity) and film thickness is studied through optical microscopy and stylus-based profilometry of glass microscopy slides and printed circuit board (PCB) sprayed coupons. PCB sprayed coupons are explored for potential use in quantifying conductivity of various CPC mixtures with greater precision and repeatability. Nominal and strained outputs of these PCB coupons are analyzed and compared to existing stochastic model outputs. The effects of CPC mixture preparation parameters on the produced outputs are investigated, and a potential method for the quantification of mixture quality and content, using the aforementioned stochastic model, is presented. Films are furthermore sprayed onto PCBs and embedded into fiber-reinforced polymer composite laminates for proof-of-concept. Equipped laminates are experimentally strained for investigation and quantification of sensor gauge factors. In addition, the electromechanical response of the sensors due to damage accumulation is explored via impact testing and simulated very-high-cycle-fatigue (VHCF). Methods for impact and damage localization are developed and discussed. Unobtrusiveness of PCB sensor design is examined through destructive testing of laminates equipped with sensors of various thicknesses. Finally, potential applications are identified and future works are discussed.


Development of Manufacturing and Characterization Methods for Carbon Black-Based Conductive Polymer Composite Sensors

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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