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This article investigates the interest of using in-situ piezoelectric (PZT and PVDF) disks to perform real-time Structural Health Monitoring (SHM) of glass fiber-reinforced polymer composites submitted to various tensile loadings. The goal is to evaluate the working range and SHM potential of such embedded transducers for relatively simple mechanical loadings, with the long-term aim of using them to monitor complete 3D structures submitted to more complex loadings. SHM is performed acquiring the electrical capacitance variation of the embedded transducers. To study the potential links between the in-situ capacitance signal and the global response of the loaded host specimens, a multi-instrumentation composed of external Nondestructive Testing techniques was implemented on the surfaces of the specimens to search for multi-physical couplings between these external measurements and the capacitance curves. Results confirmed the non-intrusiveness of the embedded transducers, and allowed estimating their working domain. PZT capacitance signal follows well the mechanical loadings, but the piezoceramic transducer gets damaged after a determined relatively low strain level due to its brittleness. The limits of this working domain are extended by using a stretchable PolyVinylidene Fluoride (PVDF) polymer transducer, allowing this one to perform in-situ and real-time SHM of its host tensile specimens until failure. [ABSTRACT FROM AUTHOR]

Abstract This article aims to provide a general overview of what has been achieved recently in the scientific community on the manufacturing monitoring and structural health monitoring of polymer-matrix composites (PMC) using in-situ piezoelectric sensors. Some industrial applications with the underlying issues and potential solutions will finally be discussed in the concluding section. [ABSTRACT FROM AUTHOR]

Abstract This paper aims the investigation of the damage monitoring by the piezoresistive effect of the tufting threads in the sandwich structures. This novelty is an additional advantage besides the primary interest for inserting tufts in composite structures that concerns the improvement in the interlaminar fracture toughness. Tufting process reinforced through-thickness the polystyrene foam core and glass fiber sheets. Electrical measurements monitored the specimens through the tufted carbon threads during flatwise compression and low-velocity impact tests for evaluating the strain-sensing and damage response. The irreversible resistance change and infrared thermography (IRT) methods analyzed the damage extent in the tufts after impact tests. IRT characterized the damages from the concentration of temperature on the deteriorated regions of the tufts while injecting electrical current. These results were validated by the ultrasonic C-Scan maps that displayed the major damages in the same zone found on IRT technique. The present study validates the capability of the approach to monitoring strain and damage events by the tufts when subjected to compressive loading. The method also presents efficient to monitor the loading and damage detection, by the irreversible resistance change, under impact tests. [ABSTRACT FROM AUTHOR]

Abstract The present paper investigates the damage monitoring using the piezoresistive effect on the glass fiber-reinforced polymer (GFRP) omega stringers reinforced through-the-thickness by tufting. The experiments consisted of the electric resistance measurements from the tufted yarns during the pull-off tests on omega stringers. Acoustic emission (AE) and digital image correlation (DIC) techniques were also performed throughout the tests in order to evaluate the acoustic activity and the strain field respectively. Furthermore, non-supervised AE clustering was carried out and aided to determine the main damage events. The results presented that electric resistance measurements are in good correlation with the AE clusters, especially with those related to the delamination and tuft yarns fracture. Besides, these damage events are well distinguished from the electric resistance data. Also, DIC images exhibited that electric resistance is sensitive to local strain field as expected to piezoresistivity measurements. Therefore, tufting reinforcements have shown to be an interesting monitor of the structural health in real time, further their well-known ability to increase the mechanical out-of-plane properties of laminate composites. [ABSTRACT FROM AUTHOR]