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

Electro-thermal–mechanical performance of a sensor based on PAN carbon fibers and real-time detection of change under thermal and mechanical stimuli

Structural health monitoring (SHM) is a vastly growing field consisting of sensors embedded in or attached with the structure which respond to the strain or other stimuli to monitor the deformation in real-time. In this study, a carbon fiber (CF) sensor was developed using unidirectional Polyacrylonitrile (PAN) carbon filaments aligned straightly together and its sensitivity was calculated experimentally, with the gauge factor (GF) in 10.2–10.8 range. The electro-thermal behavior of this CF sensor showed distinct performance and detected the change in the surrounding temperature. There is a good reproducibility in the results in both piezoresistive and electro-thermal behavior of the CF sensor and its electrical performance showed real-time detection of both mechanical and thermal stimuli. The results established that the CF exhibited good potential as a flexible strain sensor for in-situ monitoring of damage or energy release during the failure of composites

Multi-mode real-time strain monitoring in composites using low vacuum carbon fibers as a strain sensor under different loading conditions

Structural health monitoring is a vastly growing field consisting of sensors embedded in or attached with the structure which respond to the strain or other stimuli to monitor the deformation in real-time. In this study, a multi-mode strain detection is carried out in composites using nanomaterial-based sensor technology. A Carbon fiber (CF) sensor was developed using unidirectional carbon filaments aligned straightly together and its sensitivity was calculated experimentally, with gauge factor (GF) in 10.2–10.8 range. Then, this CF sensor is embedded gradually at different directions i.e. 0°, +45°, 90°, −45° between the plies of composite for real-time/in-situ strain monitoring. The composite specimen was then cut in star profile, each leg demonstrating the direction of the CF sensors. These composite samples are then tested under tensile and flexural cyclic loading. There is a good reproducibility in the results and the mechanical response of composite correlated perfectly with the electrical resistance of the CF sensor. It can also be noted that the sensors, depending on their respective position, manage to faithfully reproduce the mechanical behavior of the specimen tested (traction/compression). The results established that the CF exhibited good potential as flexible reinforcement for in-situ monitoring of composites and can provide detection over large sections and unapproachable locations. This study also showed that direction and position of the sensor plays a vital role in the detection, identification (whether its tensile or compressive) and quantification of the deformation experienced by the structure under different loading conditions

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

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Développement d'une nouvelle génération de capteurs pour la surveillance de la santé structurale des composites en temps réel

Composites have substituted traditional materials in almost every engineering and structural application because of their extraordinary performance but still, they are not exempt from limitations and problems. Despite being a multiphase material, their mechanism of damage initiation and propagation leading to failure are well established and the problem is that these damages or failures are not visible always. So, even when the overall structure is still intact, it is essential to study their performance during operational conditions in real-time to avoid any catastrophic incident. Thus, in-situ structural health monitoring was developed in which structural data can be collected and analyzed in real-time to identify the presence of damage. The study conducted in this research is within the framework of development affective and robust sensor system which can monitor not only the deformation in composite structures in real-time but also can detect damage initiation and damage propagation under different loading conditions. In this study, three different sensor systems are developed using smart functional materials to study their effectiveness in monitoring deformation in composites in different directions and positions under different quasi-static loadings. An additional goal of this research was to study the detection behavior of each sensor system and demonstrate whether they can identify the type of deformation besides their detection in real-time. The results established that each sensor system exhibited good potential as a flexible strain sensor for in-situ monitoring of composites and their arrangement can provide detection over a large section and unapproachable locations. The comparison of their results assisted in the selection of better sensor systems which is then utilized to detect damage and final fracture in composites during overall mechanical behavior under quasi-static and dynamic loadings. This study provides a comprehensive understanding regarding the detection behavior of different sensor systems under different operational loads and also shows that the position and direction of the sensor within the sample plays a vital role in it. Based on this detailed comparison, the selected sensor system does not only monitor the deformation in real-time but also, detect damage initiation, identify the type of damage, quantifies them, and also sense damage propagation under both quasi-static and dynamic loadings. Moreover, numerical models are developed to verify the detection behavior of this sensor system to verify the experimental results. Numerical results not only validated the experimental mechanical behavior of the composite sample but also confirmed the detection signal of the sensor placed in different positions and directions within the composite sample. This research study has resulted in several publications in rank A journals (6 articles), 1 chapter in a book, 1 publication in SPIE digital library, and 5 oral presentations in different conferences.Les composites ont remplacé les matériaux traditionnels dans presque toutes les applications d'ingénierie et de structure en raison de leurs performances extraordinaires, mais ils ne sont pas exemptes de limitations et de problèmes. Bien qu'il s'agisse d'un matériau polyphasé, les mécanismes d'initiation et de propagation des dommages conduisant à la rupture est bien établi et le problème est que ces dommages ou défaillances ne sont pas toujours visibles. Ainsi, même lorsque la structure globale est toujours intacte, il est essentiel d'étudier ses performances en conditions opérationnelles en temps réel pour éviter tout incident catastrophique. Ainsi, une surveillance de la santé structurelle in-situ a été développée dans laquelle les données structurelles peuvent être collectées et analysées en temps réel pour identifier la présence de dommages. L'étude menée dans le cadre de ce travail de thèse s'inscrit dans le cadre du développement d'un système de capteurs sensible et robuste qui peut non seulement surveiller la déformation des structures composites en temps réel, mais aussi détecter l'initiation et la propagation des dommages sous différentes conditions de charge. Dans cette étude, trois systèmes de capteurs différents ont été développés en utilisant des matériaux fonctionnels intelligents pour étudier leur efficacité dans le suivi de la déformation des composites dans différentes directions et positions sous différente type de chargement. Un objectif supplémentaire de ce projet est d'étudier les performances de détection de chaque système de capteurs et de démontrer s'ils peuvent identifier le type de déformation en plus de leur détection en temps réel. Les résultats ont établi que chaque système de capteur présentait un bon potentiel en tant que capteur flexible de contrainte pour la surveillance in-situ des composites et leur disposition peut fournir une détection sur une grande section et des emplacements inaccessibles. La comparaison des résultats de la campagne d’essais a permis de sélectionner les meilleurs systèmes de capteur qui sont ensuite utilisés pour la détection des dommages dans les composites sous l’action des charges statiques et dynamiques. Cette étude donne une vision complète concernant le comportement de détection de différents systèmes de capteurs sous différentes charges opérationnelles et montre également que la position et l’orientation du capteur dans l'échantillon jouent un rôle vital. Sur la base de cette comparaison détaillée, le système de capteurs sélectionné surveille non seulement la déformation en temps réel, mais permet également de détecter le déclenchement et la propagation des dommages ainsi que d’identifier et quantifier leur nature sous des chargements statiques et dynamiques. De plus, des modèles numériques robuste ont été développés et corréler avec les résultats expérimentaux. Les résultats numériques ont non seulement validé le comportement mécanique expérimental de l'échantillon composite, mais ont également confirmé le signal de détection du capteur placé dans différentes positions et directions au sein de l'échantillon composite. Ce travail de recherche a donné lieu à plusieurs publications dans des revues de rang A (6 articles), 1 chapitre dans un livre, 1 publication dans la bibliothèque numérique SPIE et 6 présentations orales dans différentes conférences

Fabrication and electromechanical performance of carbon nanotube based conductive membrane and its application in real-time multimode strain detection in composites

In this study, a flexible conductive membrane (CM) consisting of a network of carbon nanotubes is produced and the electromechanical behavior of this CM was studied experimentally and the gauge factor (GF) of CM was in the 8–8.25 range. Then, a multi-mode strain detection is carried out in composites using this CM sensor. The CM is embedded gradually at directions i.e. 0°, +45°, 90°, −45° between the plies for real-time/in-situ strain monitoring. The composite specimens are then cut in star profile and then tested under tensile and bending cyclic loading. There is a good reproducibility in the results and the mechanical response of composite correlated perfectly with the electrical resistance of the CM sensor however, a sensor in each position showed distinct behavior. The results established that the CM sensor exhibited good potential as a flexible strain sensor for in-situ monitoring of composites and can provide detection over a large section and unapproachable locations

Background, advancement, and applications of in situ structural health monitoring based on different modes of failure detection in composites

Vast investigation had been going on for the past few years to overcome the gap that still hinders real-time failure detection of composites in applications such as wind turbines and their components. However, real-time monitoring has been made more applicable with the advancement of smart materials and nanotechnology thus emerging as a possible solution for better in situ monitoring of these materials in their specific application. In addition, there is another important aspect on which structural health monitoring (SHM) can be classified which includes the selection of in situ SHM techniques for specific loading conditions such as vibration loads, compression, bending, etc., and failure behaviors such delamination, reinforcement failure, matrix cracking, etc., that has limited information in the literature. This chapter provides a summary of how the introduction of nanomaterials and the development of nonmaterial approaches have revolutionized real-time SHM technology. Then, an extensive literature review on the specific applications of these advanced in situ SHM techniques to detect and monitor damage in composites under different static/quasi-static/dynamic loading parameters. This is the main objective of this article and will benefit the researchers in the selection of in-situ SHM techniques best suitable for specific damage detection in composite structures. This study is important for better durability, safety, and sustainability of operational structures such as wind turbines

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

International audienceSmart 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