Abstract
The laser linear scanning method is proposed to measure the modal shape of fiber-reinforced composite thin plate with high efficiency and precision. First, by establishing the laser scanning frame model of the composite plate, the corresponding extraction principle of modal shape data and laser scanning rate selection criterion are explained in detail to clarify the theoretical principle of laser linear scanning method. The corresponding test procedure of modal shape, drawing method from the shape scanning data, and control method of the constant laser scanning rate are also proposed based on the developed laser linear scanning system. Then, a TC300 carbon fiber/resin composite thin plate is taken as a research object to verify the effectiveness and reliability of such a method, through comparing the results obtained by the traditional experimental modal method and finite element method. Moreover, the influences of constraint boundary condition, excitation level, laser scanning rate, scanning spacing, scanning path mode, the fiber angles, and fiber material damage on modal shape results are also discussed. It has been found that laser linear scanning method can improve test efficiency of modal shape of the composite plate with high preciseness. Except for scanning path mode, the other parameters have a major impact on each shape morphology, and their effects can be quantitatively analyzed by identifying the positions and clarity of nodal lines of each modal shape. Especially, the high-density modal shape results and their equal amplitude lines in different projection views can be used to determine whether or not the composite plate is damaged as well as its damaged degrees.
Highlights
The fiber-reinforced thin plate structures have been gradually used in aeronautics, astronautics, automobile, ships, weapons, and other industrial fields1,2 due to the high specific strength and modulus, good thermal stability, high bearing capacity, and lightweight
The experimental modal analysis theory has been mainly employed to measure the modal shapes of fiber-reinforced composite structures, which is realized by combining the frequency response function measurement method with modal parameter identification method
Oh and Nayfeh5,6 tested modal shapes of a fiber-reinforced composite thin plate by using hammer and laser vibrometer, and found that the most of the modal shapes can be obtained by this technique
Summary
The fiber-reinforced thin plate structures have been gradually used in aeronautics, astronautics, automobile, ships, weapons, and other industrial fields due to the high specific strength and modulus, good thermal stability, high bearing capacity, and lightweight. Define the rations of the response and reference signals as the transmissibility function, and its expression is given as follows point begins to move, and tcom represents the end time of the laser scanning process in each row. Assuming that each modal shape measurement of fiberreinforced composite thin plate is finished by row scanning path mode, the total number of measurement points in each row of frame model In the row scanning path mode, in order to draw the modal shape model conveniently, usually we need to ensure that the distances between adjacent scanning points are equal in the x and y directions, that is, YM = XN. Equation [20] can be simplified as l u=
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