Silicon carbide fiber network-based self-sensing and microwave-absorbing composite structures

Abstract

Composite materials which are composed of two or more different materials have driven the advancement in multi-functional structures. Among multi-functional composite structures, functional fiber-based multi-functional composite structures can have advantages in the fabrication process and consistent multi-functional performance. However, due to the lack of functional fibers with excellent multi-functionality, researches were limited. Silicon carbide (SiC) fibers, which have attracted many interests because of their superior mechanical property and thermal resistance, are expected to have excellent multi-functional characteristics in piezoresistivity and microwave loss characteristics due to their semi-conductive characteristics. Therefore, this study investigated the multi-functionality of SiC fibers and its applications. The sensor application of SiC fibers with excellent piezoresistivity was studied, and the SiC fiber network-embedded composite structures for simultaneously self-sensing and microwave-absorption was proposed and investigated. First, the application of SiC fibers as an embedded sensor for composite structures was studied. Prior to the sensor application, the strain sensing properties of SiC fibers were experimentally evaluated. Through the tensile testing of SiC fiber embedded composite specimens, the resistance change of the SiC fibers was measured according to the applied mechanical strain, and the strain sensing properties of the SiC fiber were evaluated. As a result, the SiC fibers showed outstanding strain sensitivity with GF of 8.25 and excellent linearity up to the strain range of 1.36%. As an application study of the SiC fibers as an embedded sensor for composite structures, embedded SiC fiber sensor based impact detection and localization of composite structures were performed. SiC fiber sensor network-embedded composite panels were fabricated. Impact signals were successfully acquired by the embedded SiC fiber sensors, and the characteristics of acquired impact signals were analyzed. As a result, the SiC fiber sensor showed the inherent signal characteristic that impact signals acquired at points with similar normal distances from the sensing fiber cannot be differentiated in its resistance change. Thus, the reference data based impact localization using the embedded SiC fiber sensors showed large errors. However, through mutual compensation between the SiC fiber sensors configured considering the similar impact signal distribution characteristics, reference data based impact localization could be successfully performed. Consequently, the SiC fibers showed excellent strain sensing performance, and the application of SiC fiber sensors for impact detection and localization of composite structures was successfully performed. Second, by leveraging the excellent piezoresistivity and microwave loss characteristics of SiC fibers, a SiC fiber network-based self-sensing and microwave-absorbing composite structure was proposed and investigated. The SiC fiber network-embedded composite structure, which can allow individual SiC fiber yarns to act not only as microwave lossy materials but also as piezoresistive sensors, was proposed and its design, fabrication and performance verification were investigated. Through the full-wave simulation of SiC fiber network-embedded composite model, the design parameters of SiC fiber network-embedded composite were investigated. As a result, the microwave loss characteristics of SiC fiber network-embedded composite could be controlled by the spatial arrangements of SiC fiber network. Based on the simulation results, the SiC fiber network-based self-sensing and microwave-absorbing composite structure was designed. This designed structure was fabricated and its self-sensing and microwave-absorbing performances were experimentally verified. The microwave return loss of the fabricated SiC fiber network-embedded composite structure was measured, and dynamic signal acquisition using the embedded SiC fiber sensors and impact localization of the SiC fiber network-embedded composite structure using embedded SiC fiber sensor network were performed. As a result, the fabricated SiC fiber network-embedded composite structure successfully demonstrated the designed self-sensing and microwave-absorption performances. In addition, the mechanical testing of SiC fiber network-embedded composite was performed, and the results showed that the embedded SiC fibers contribute to the load-bearing together with host composite structure. Consequently, the SiC fiber network-based self-sensing and microwave-absorbing composite structure was successfully designed and fabricated, and the multi-functional performance of the SiC network-embedded composite was successfully demonstrated. This study focused on the multi-functionality of SiC fibers and its applications. The SiC fibers showed excellent strain sensing properties, and they were successfully utilized as an embedded sensor for composite structures. An engineering design to utilize the multi-functionality of SiC fibers was implemented, and the SiC fiber network-based self-sensing and microwave-absorbing composite structure was successfully designed and demonstrated. Through further research on the multi-functionality of SiC fibers, it is expected that multi-functional composite structures with improved performances can be designed.