Wireless strain measurement for structural testing and health monitoring of carbon fiber composites

A novel device patented by Intel and called WISP (Wireless Identification and Sensing Platform) is modified to interface with a conventional foil resistance strain gage. The wireless, battery-free, digital device communicates with and is powered by an Ultra-High Frequency (UHF) RFID (Radio Frequency Identification) reader. The standard Intel WISP has been modified with the addition of a PCB (printed circuit board), which act as the analog interface with the strain gage. The so-called WISPs/g (for strain gage) has been utilized during uniaxial tension tests on carbon fiber composite specimens to compare accuracy and repeatability with conventional wired strain gage and extensometer. Validation of the technology is performed with a structural test, whereby four independent WISPs/g devices are positioned on the surface of a carbon fiber composite flat panel subjected to quasi-static indentation. Measurements are compared to the predictions of a NASTRAN finite element model (FEM) and show excellent agreement. Applications of this technology include strain measurement during static airframe tests, as well as on-board real-time strain measurements during test flight and certification of new aircraft.