All-printed strain sensors: Building blocks of the aircraft structural health monitoring system

• Published in: Sensors and actuators. A. Physical. Vol. 253; pp. 165 - 172
• Main Authors: Zhang, Yuzheng, Anderson, Nickolas, Bland, Scott, Nutt, Steven, Jursich, Gregory, Joshi, Shiv
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.01.2017; Elsevier BV
• Subjects: Aging aircraft; Aircraft; Aircraft components; Diagnostic systems; Fatigue tests; Formulations; Inkjet printing; Inks; Mapping; Measuring instruments; Monitoring systems; Parameter identification; Parameter sensitivity; Polyethylene terephthalate; Printing; Process parameters; Reliability analysis; Screen printing; Sensitivity analysis; Sensors; Serpentine; Strain gauges; Strain rate; Strain sensor; Structural analysis; Structural health monitoring; Substrates; Screen printing; Inkjet printing; Structural health monitoring; Strain sensor
• ISSN: 0924-4247; 1873-3069
• DOI: 10.1016/j.sna.2016.10.007

•Characteristics of printed strain sensors (gage factor, ink microstructure, temperature sensitivity, transverse sensitivity and fatigue response, etc.) are explored and compared with standard foil gages in this article.•The printed sensors have significantly higher gage factors than standard foil gages and exhibited excellent linearity up to 0.4% strain with fatigue resistance up to 105 strain cycles.•However, in order to employ these printed strain sensors in reliable structural health monitoring systems, their temperature and transverse-strain sensitivities need to be improved.•In addition, printing consistency with defect-free deposition and line resolution improvements will be further investigated in order to achieve reliable low-cost all-printed wide-area structural state sensing systems for practical applications.•To realize a fully integrated strain mapping system, future efforts will also be dedicated to multiplexing electronics on flexible substrates as well as integration of a printed power source and conventional electronic integrated circuitry. Characterization of all-printed strain gages to assess their suitability for structural state monitoring of large structures is presented. Strain sensor response, transverse strain sensitivity and long-term reliability are key performance parameters of printed strain sensors on flexible substrates. These key performance parameters are evaluated for inkjet and screen printed strain sensors on polyethylene-terephthalate (PET) flexible substrates. More specifically, printing characteristics of commercially available inks, gage factor of serpentine strain sensors with transverse strain and temperature sensitivity, and sensor reliability under unidirectional tensile and fatigue loading is assessed. Maximum strain to which both inkjet and screen printable formulations can be reliably used for long-term repeatable measurements is recommended based on tensile and fatigue testing. Variation in gage factor is attributed to micro- and macro-scale fracture of printed traces under mechanical loading. Substrate, ink and printing process parameters are identified to further improve strain sensing characteristics of low-cost, large area strain mapping systems. Reliable, low-cost, and large-area strain mapping systems are sought for continuous or on-demand real-time diagnosis and prognosis of complex structural components.