Real-time strain monitoring and damage detection of composites in different directions of the applied load using a microscale flexible Nylon/Ag strain sensor

Composites are prone to failure during operating conditions and that is why vast research studies have been carried out to develop in situ sensors and monitoring systems to avoid their catastrophic failure and repairing cost. The aim of this research article was to develop a flexible strain sensor wire for real-time monitoring and damage detection in the composites when subjected to operational loads. This flexible strain sensor wire was developed by depositing conductive silver (Ag) nanoparticles on the surface of nylon (Ny) yarn by electroless plating process to achieve smallest uniform coating film without jeopardizing the integrity of each material. The sensitivity of this Nylon/Ag strain sensor wire was calculated experimentally, and gauge factor was found to be in the range of 21–25. Then, the Nylon/Ag strain sensor wire was inserted into each composite specimen at different positions intentionally during fabrication depending upon the type of damage to detect. The specimens were subjected to tensile loading at a strain rate of 2 mm/min. Overall mechanical response of composite specimens and electrical response signal of the Nylon/Ag strain sensor wire showed good reproducibility in results; however, the Nylon/Ag sensor showed a specific change in resistance in each direction because of the respective position. The strain sensor wire designed not only monitored the change in the mechanical behavior of the specimen during the elongation and detected the strain deformation but also identified the type of damage, whether it was compressive or tensile. This sensor wire showed good potential as a flexible reinforcement in composite materials for in situ structural health monitoring applications and detection of damage initiation before it can become fatal

Nanotechnology and Development of Strain Sensor for Damage Detection

Composite materials, having better properties than traditional materials, are susceptible to potential damage during operating conditions, and this issue is usually not found until it is too late. Thus, it is important to identify when cracks occur within a structure, to avoid catastrophic failure. The objective of this chapter is to fabricate a new generation of strain sensors in the form of a wire/thread that can be incorporated into a material to detect damage before they become fatal. This microscale strain sensor consists of flexible, untwisted nylon yarn coated with a thin layer of silver using electroless plating process. The electromechanical response of this sensor wire was tested experimentally using tensile loading and then verified numerically with good agreement in results. This flexible strain sensor was then incorporated into a composite specimen to demonstrate the detection of damage initiation before the deformation of structure becomes fatal. The specimens were tested mechanically in a standard tensometer machine, while the electrical response was recorded. The results were very encouraging, and the signal from the sensor was correlated perfectly with the mechanical behavior of the specimen. This showed that these flexible strain sensors can be used for in situ structural health monitoring (SHM) and real-time damage detection applications

In-Situ Monitoring, Identification and Quantification of Strain Deformation in Composites Under Cyclic Flexural Loading Using Nylon/Ag Fiber Sensor

Despite having vast structural applications, Composites are not exempt from limitations and are susceptible to deforming during operation. Therefore, it is essential to develop in-situ monitoring systems to avoid their catastrophic failure or high repairing cost. So, the objective of this study was to monitor the deformation behavior of composites subjected to cyclic flexural deformation in real-time using a Nylon/Ag fiber sensor. Nylon/Ag fiber sensor was integrated at different direction i.e. 0°, +45°, 90°, -45° gradually between each ply of the composite specimens which were then machined in star shape where each leg signified the direction of the sensor. These specimens were then tested under cyclic flexural deflection at the strain rate of 2mm/min for 10 cycles. Mechanical results of composite specimens and electrical response of each Nylon/Ag sensor fiber showed excellent repeatability however, each Nylon/Ag fiber sensor showed a specific resistance behavior because of their respective position. The increase or decrease in the resistance of the fiber sensor signified the presence of tensile or compressive strain respectively and the intensity of the signal quantified the amount of deformation. The results confirmed that the fiber sensor showed good potential as flexible sensor reinforcement in composites for in-situ monitoring, identification and quantification of the deformation

Nylon/Ag fiber sensor for real-time damage monitoring of composites subjected to dynamic loading

In this article, the goal is to monitor the deformation and damage behavior of composites in real-time using a Nylon/Ag fiber sensor when subjected to dynamic loading. Composite samples are integrated with Nylon/Ag fiber sensors at distinct locations and directions between the plies. Then, these samples are experimentally impacted with low-velocity impact using the Taylor Cannon Gun apparatus at three different velocities i.e. 2.5 m s−1, 3 m s−1, and 6.5 m s−1, respectively. These three sets of tests are conducted to determine the detection performance of the Nylon/Ag fiber sensor when the composite sample experiences no damage, some microdamage, and overall breakage. Besides, the fiber sensor placed in each position showed distinct electrical behavior in all three tests and detected the deformation, damage initiation, quantification, identification, and damage propagation. The results confirmed the ability of the fiber sensor to monitor and identify the mechanical deformation during dynamic loading and showed that the sensor can be used as a flexible sensor reinforcement in composites for in-situ monitoring as well

Development of microscale flexible nylon/Ag strain sensor wire for real-time monitoring and damage detection in composite structures subjected to three-point bend test

Composite are prone to failure during operation and that's why vast research had been carried out to develop in-situ sensors and monitoring systems to avoid their catastrophic failure and repairing cost. The aim of this research was to develop a flexible strain sensor wire for real-time damage detection in the composites. This strain sensor wire was developed by depositing conductive silver (Ag) nanoparticles on the surface of nylon (Ny) yarn by electroless plating to achieve the smallest uniform coating without jeopardizing the integrity of each material. The sensitivity of this Ny/Ag strain sensor wire was calculated experimentally and gauge factor (G.F) was found to be in the range of 21–25. Then, Ny/Ag strain sensor wire was inserted in each composite specimen at different position intentionally through the thickness during their fabrication depending upon the type of damage to detect. The specimens were subjected to flexural deflection using a 3-point bend test at the strain rate of 2 mm/min. Overall mechanical response of composite specimens and electrical response signal of the Ny/Ag strain sensor wire showed good reproducibility in results however, Ny/Ag sensor showed a specific change in resistance in each specimen because of their respective position. The sensor wire designed, did not only monitor the change in the mechanical behavior of the specimen until final fracture but also identified the type of damage whether it was compressive, tensile or both. This sensor wire showed good potential as a flexible reinforcement in composite materials for in-situ SHM applications before it can become fatal

Real-time strain monitoring performance of flexible Nylon/Ag conductive fiber

Smart textiles have generated significant importance because of the advent of portable devices and easy computing, however, they did not replace the conventional electronics on the whole however, this development is now advanced to the fabrication of wearable technologies. The aim of this research paper was to develop a flexible microscale conductive fiber for real-time strain monitoring applications. This conductive fiber was developed by depositing conductive silver (Ag) nanoparticles on the surface of Nylon-6 polymer yarn by electroless plating process to achieve smallest uniform coating film over each filament of the Nylon yarn without jeopardizing the integrity of each material. The sensitivity of this Nylon/Ag conductive fiber was calculated experimentally and gauge factor was found to be in the range of 21–25 which showed that it had high sensitivity to the applied strain. Then, Nylon/Ag conductive fiber was tested up to fracture under tensile loading and a good agreement between mechanical and electrical response was observed with reproducibility of the results. The results demonstrated the way to design a cost-effective microscale smart textile for strain monitoring. This Nylon/Ag conductive fiber can then be used in a wide range of high strain applications such as in-situ structural health monitoring or for medical monitoring because of their high sensitivity, flexibility, and stability

In-situ damage monitoring of composites under dynamic impact using nylon/Ag fiber sensor

International audienceDespite having a vast structural application, Composites are not exempt from limitations and are also susceptible to deforming during operations. Therefore, it is essential to develop in-situ monitoring systems and sensors to avoid their catastrophic failure, especially for dynamic failure. So, the objective of this study was to investigate and monitor the dynamic behavior of composites in real-time using a Nylon/Ag fiber sensor under the low-velocity impact. Nylon/Ag fiber sensors were integrated at different directions and positions within the composite specimens which were tested under low-velocity impact on the Taylor cannon gun apparatus. Three sets of tests were performed at 2.5m/s, 3m/s and 6.5m/s respectively to demonstrate the detection signal of the fiber sensors when there is no damage, some micro damage and overall breakage of the sample. The results confirmed that each Nylon/Ag fiber sensor showed a specific resistance behavior in all three specimens because of their respective position and direction and detected the deformation, damage initiation, damage propagation, type of damage and quantification of the amount of damage induced