DEFORMATION CONTROL METHOD OF COMPOSITE STRUCTURAL ELEMENTS BY FIBER-OPTIC ACOUSTIC EMISSION SENSOR

Abstract

Subject of Research.The paper presents the study of a graphite-epoxy composite plate strain detection possibility by the fiber-optic acoustic emission sensor mounted on its surface. Method. The proposed method consisted in additional low-frequency phase-generated carrier implementation in the impulse Fabry-Perot interferometer and its amplitude evaluation. The phase-generated carrier amplitude depends on the interferometer optical path difference, therefore, its value change can be used for the studied composite strain estimation. VCSEL with a wavelength of 1550 nm was used as a light source. The phase carrier was generated by current modulation of the light source that caused center wavelength shift of the VCSEL. Main Results. The low-frequency phase-generated carrier signal amplitude dependence on the interferometer optical path difference and wavelength shift of the light source were obtained. According to simulation results the sensitivity of the proposed method is 1.6 urad×ppm, 5.3 urad×ppm and 13.3 urad×ppm at different values of the coefficient Kd 30, 100 and 250 pm, respectively. Experimental study of the proposed method and results analysis were performed. According to experimental results, the accuracy of the proposed method was about 1´10–3% that corresponds to the sensor relative stretch of 10 me, while the accuracy of the market available fiber optic systems based on fiber Bragg grating sensors equals to 4 ppm. Practical Relevance.The proposed method can be used for strain detection of the graphite-epoxy composite constructions along with its acoustic emission control by one fiber-optic sensor.

Keywords

• fiber-optic sensor
• impulse Fabry-Perot interferometer
• graphite-epoxy (Gr/Ep) composite
• strain sensor
• acoustic emission sensor
• fiber Bragg grating (FBG)