Use of Sensor Technology in Composites

Sensor Technology in Composites Rising demand proportional to increasing population, coupled with accelerated production, increases the risk of manufacturing errors. Experts continue efforts to prevent these errors through advance prediction and achieving uniform production. Digital tools emerge at this point. Especially with digitalization, greater monitoring of data and faster transmission have been enabled, creating the opportunity for error-free production. Composite materials are utilized in many fields. In particular, due to properties such as high strength, thermal stability, corrosion resistance, light weight and impact resistance provided by these materials, the use of composite materials in load-bearing structures and vehicles is increasing daily. Their use in carriers such as aircraft, automobiles and unmanned aerial vehicles has made it necessary for composite materials to undergo rigorous inspections. At this point, researchers have foreseen that sensors could be utilized and have begun research on this matter. A large portion of research has focused on monitoring the curing phase. With sensors controlling; production stages, physical and thermodynamic behavior and process conditions, composite materials can be produced more widely. In particular, fiber Bragg grating systems have been observed to be applicable as sensors in the control of composite materials.

Fiber Bragg Grating Sensors

Fiber Bragg Grating sensors can be used by embedding them inside composite materials. These sensors are produced using various technical methods in specific sections of single-mode standard fiber optic cables with cores up to 9 micrometers and cladding diameter of 125 micrometers, creating periodic refractive index modulation (1mm-10mm in length). They are used especially to control next-generation space and aircraft during flight. Beyond this application area, FBGs are also embedded in cities within asphalt, concrete and asphalt. At the same time, FBG sensors are utilized on highways, bridges, railways, and in gas and oil pipelines to monitor strains occurring along the lines and to intervene early in damaged areas when necessary. To explain application areas more broadly; FBGs are utilized in buildings, wind turbines, energy fields, maritime, safety and security applications, medical field, transportation, laboratory tests and measurements. Among these fields listed, composite materials are frequently utilized particularly in energy, transportation and maritime sectors. To convey the purposes for which FBGs are used in these fields, for example, in wind turbines they are utilized in structural health monitoring of blades, real-time control and observation of operating conditions.

Advantages of FBG Use

Looking at the advantages provided by these sensors, in particular low installation cost; small size, flexible and light structure and high-precision test results are among the advantages and are the main reasons for preferring these sensors. At the same time, FBGs can measure over long distances, measure different physical parameters simultaneously and be applied in different fields. Among their other advantages are; immunity to electromagnetic and radiofrequency interference, ability to measure from different points along the fiber line, no requirement for electrical power and ability to obtain real-time measurements.

New Sensor Technology Developed

Not only FBG but many types of sensors are used in composite applications and research is being conducted on this matter. For example; the National Composite Centre of the United Kingdom, Cranfield University and aerospace engineering expert Meggitt conducted a collaboration on this matter. As a result of the collaboration, new sensor technology was developed to collect data during the liquid resin process. Dr. Alex Skordos, lecturer in the Composite Process Science Lectureship at the Cranfield University School of Aeronautics, Space, Transport and Manufacturing, conducted initial research on dielectric sensors. Subsequently, this research was further developed in the composite research center through testing and was applied in industry by Meggit. This sensor system enables resin infusion to capture accurate data, thereby facilitating digitalization of the Resin Transfer Molding method. Use of this sensor facilitates the production process; contributes to obtaining the correct approach on the first attempt, reducing time spent on production and lowering production costs. When developing these new sensor types, detailed testing was also conducted. The tests conducted were performed under 7 Bar and 180 degree aerospace material processing conditions. According to the testing conducted under these conditions, the sensor was able to precisely detect the resin and cure progression as it flowed within the preform. At the same time, the sensors created no negative impact on process or part quality. Seeing the success of the tests conducted, Meggit applied to use these sensors in a project. As a result, engineers sharing their views reported that the sensors were quite robust and effective during demonstration on a large-scale composite fuselage part designed for a civil aviation jet engine air-oil heat exchanger. Development of composite materials brings advances particularly in space and aviation fields. Research conducted has shown that sensors; provide reliable data on the behavior of composite materials and at this point facilitate the production and maintenance process. It has been observed that the use of sensors in composite materials provides benefits such as shorter maintenance periods, reduced costs and higher reliability. Experts emphasize that development of new sensors is important for achieving better targets in composite production.

CO2 Sensor from Composite Material

Composite materials are utilized in many fields as emphasized above. While the use of sensors in composite materials brings many advantages, as a result of research conducted in recent years, a new composite material was produced that could be used as a CO2 sensor. The conductivity of this material changes according to the carbon dioxide density in the environment. Material science researchers from ETH Zurich and the Max Planck Institute for Colloids and Interfaces in Potsdam developed this material for use as a sensor. In addition to being very small and simple in structure, this new type requires much less energy compared to other sensors. The material, which can be referred to as a new type sensor produced as a composite material, consists of a fig-type polymer and a fluid, as well as a type of salt called ionic liquid that is conductive at room temperature. These materials, designated as [Poly(ionic liquid)s] (PIL), have different application areas being investigated by scientists. It was known that PIL has a structure that absorbs carbon dioxide, and experts, based on this property, worked to develop a new gas sensor by providing information about carbon dioxide density in air. Scientists succeeded by combining polymers with specific inorganic nanoparticles known to interact with carbon dioxide. With the aid of the newly produced sensor; carbon dioxide density can be measured over a wide range from 0.04 percent volume in Earth's atmosphere to 0.25 percent volume. At the same time, because the newly produced sensor is much smaller and portable, less energy is consumed in its use compared to other sensors. References: Compositesworld.com Fiber Optic Based Sensor System Design and Analysis for Monitoring Production Processes in Composite Materials; Anıl Yılmaz, Osman Kartav, Kıvılcım Yüksel https://inovatifkimyadergisi.com/kompozit-malzemelerde-sensor-teknolojisi https://www.eonphotonics.com/tr-TR/Urun/FBG_TR https://bilimvegelecek.com.tr/index.php/2015/07/01/co2-sensoru-olarak-yeni-bir-kompozit-materyal-2/ https://www.compositesworld.com/articles/sensors-data-for-next-gen-composites-manufacturing Prepared by: Nilsu Kotil