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

Abstract

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.

Preparation and Characterization of Polypropylene/Carbon Nanotubes (PP/CNTs) Nanocomposites as Potential Strain Gauges for Structural Health Monitoring

“…Furthermore, an important advantage in the preparation of PP/CNT strain-sensors lies in their flexibility. As reported elsewhere, it is important to have flexible strain-sensors in order to be easily used in several fields of application [51,52].…”

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

“…After that, reduction process in ammonia (NH 3 ) environment was carried out for a period of 2 hours which reduced the Ag(I) to Ag(0) ions and finally, silver nanoparticles were deposited on the surface of nylon. Scanning electron microscopy (SEM) further verified the homogeneous deposition of Ag nanoparticles on every filament of the Nylon yarn [64], Figure 2. Then the fiber sensor was cut into specific length and was inserted between the plies of chopped glass fibers in their respective position and direction during the fabrication of the composite specimen.…”

“…However, application of Ag coated fabric regarding SHM of composites is still limited. Y. Qureshi et al [62,63] recently investigated the application of Ag coated nylon yarn as strain sensor under tensile loading and found that the position of Nylon/Ag sensor wire played an important part in identification of type of strain and damage [64]. Moreover, they also found out in their extended study that position of Nylon/Ag sensor wire, at different locations through thickness in respective specimens but in same direction, differentiated in type of strain and damage in each specimen subjected to flexural loading up to fracture [65].…”

Methods of modifying through-thickness electrical conductivity of CFRP for use in structural health monitoring, and its effect on mechanical properties – A review

“…Qureshi et al [92] have shown that silver coated nylon yarns can be used as strain sensors within GFRPs. They coated nylon yarns with silver nano-particles and placed them within the GFRPs during manufacturing.…”