Method for calculating thermal expansion coefficient of composite plate based on optical fiber strain conversion matrix

Abstract

The invention provides a method for calculating thermal expansion coefficient of a composite plate based on an optical fiber strain conversion matrix and belongs to the field of structure health monitoring. The method provided by the invention comprises the following steps: firstly, defining a coordinate system of the surface of a to-be-tested composite plate and arranging an optical fiber sensing network; secondly, constructing a conversion matrix between thermal strain received by a grating and central wavelength shift; thirdly, constructing a conversion matrix between thermal strain of a composite plate structure and the central wavelength shift of an optical fiber grating; fourthly, acquiring a response signal of an optical fiber grating sensor under variable temperature condition; fifthly, calculating thermal strains in i and j directions of a to-be-tested composite plate structure; and sixthly, determining the thermal expansion coefficient of the to-be-tested composite plate structure. The calculation method provided by the invention builds a thermal expansion coefficient calculation model for the composite plate structure and can determine the thermal expansion coefficient of the composite plate structure in the to-be-tested direction. The method provided by the invention is simple and easy, high in accuracy and good in reliability.

Description

technical field [0001] The invention belongs to the field of structural health monitoring, and specifically proposes a method for measuring the thermal expansion coefficient of a composite material plate structure based on an optical fiber strain conversion matrix. Background technique [0002] Composite material is a new type of advanced structural material, which has good dimensional stability and durability in special environments, and has been widely used in engineering. Thermal expansion coefficient is one of the important physical properties of materials. It is used to directly characterize the volume change of substances caused by temperature changes, and has an important impact on structural health monitoring and service life assessment. When under the action of temperature load, the structure undergoes heat radiation and conduction in the radial direction, and due to the existence of temperature gradient inside the material, thermal strain will inevitably occur, res...

AI Technical Summary

Problems solved by technology

The mechanical method usually uses a fixture to fix the specimen, but the fixture itself is easily deformed by heat and affects the measurement accuracy

Moiré interferometry needs to engrave a precise diffraction grating on the sample, and observe the diffraction fringes of the specimen through a complex external optical system, but the external optical system is easily affected by the external environment and reduces the measurement accuracy

Because the traditional FBG model only considers the longitudinal strain measured by the fiber Bragg grating sensor when it is used to measure the thermal expansion coefficient of materials, but in the measurement of the thermal expansion coefficient of composite materials, the transverse strain often leads to significant deviations

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