초탄성 변형율 측정을 위한 탄소나노 복합소재 스트레인 센서 설계 연구

Abstract

A hyperelastic material such as a rubber shows large strain and non-linear stress-strain behaviors. When an external force is applied to the rubber, it exhibits hyperelastic behavior, a non-linear relationship between the load and its mechanical deformation. For this reason, the rubber is utilized as an anti-vibration and anti-noise component in industries. Although the rubber contributes to various mechanical parts, its design with experimental still suffers because of its non-linear behavior due to hyperelasticity and complicated manufacturing conditions.Therefore, in-situ sensor technology for hyperelastic materials has been required in field engineering to evaluate their mechanical characteristics. A foil-type strain gauge, a popular commercial deformation sensor, is only available within limited low strain levels (<0.5%) and with poor durability. To measure the hyperelastic material's large strain (>20%) involving non-linear mechanical behavior, novel sensor technology should be studied to overcome the conventional problems. This dissertation studied a Nano Carbon Strain Sensor (NCSS) design based on its piezoresistive mechanism for hyperelastic mechanical deformation. As a Nano Carbon Composite (NCC) is deformed under an external load, its electrical conductivity changes due to its internal nano-filler condition variations, known as piezoresistivity. The NCSS can be a promising in-situ sensor to measure non-linear behaviors of the hyperelastic material under large deformation. The main design factors of NCSS can be represented by the matrix characteristics for its stiffness/softness, the composite fabrication conditions for improving sensing characteristics, and the geometrical sensor shape design for sensing performances. To apply hyperelastic strain deformation, the NCSS installed hyperelastic components for vehicle parts such as tires, bushing, and jounce bumper. The NCSS hyperelastic sensing characteristics were experimentally studied about its design parameters. The geometric pattern and shape profile of NCSS was studied to design its hyperelastic strain sensing characteristics. 2-dimensional (2D) grid types examined the NCSS pattern design for high durability (>1000 cycles) and linear sensing performance. Furthermore, a 3D printed sensor with a curvature profile was designed, and it successfully measured the hyperelasticity over 100 % strain. In conclusion, the NCSS can measure hyperelastic mechanical deformation with high durability and linear sensing performance, and its sensing characteristics can be designed by its geometric pattern and shape design.