PSI - Issue 36

O.L. Derkach et al. / Procedia Structural Integrity 36 (2022) 71–78 O.L. Derkach et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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Fig. 4. Dependencies of the principal frequency variation Δ p d of flexural vibrations on the angle of the fibers of the damaged ( a = 0.6; C x = 0.1) beam at the initial value (1) and 10 times increased values (2) of shear modulus of the matrix of the composite. Thus, it is crucial to consider the peculiarities of deformation in composite beams with damages. It defines the character of dependencies of the variation of their natural frequencies on the anisotropy of the elastic properties. However, the conclusion on the character of the presented dependencies can be made using the results of the experimental investigations of vibrations of these beams. Let us consider the results of calculation experiments on the determination of the influence of relative position C x on the principal frequency of flexural vibrations in the range of its variation from 0.05 to 0.95. Such investigations were performed at the relative depth of the notch a = 0.2 for the beams with the angle of the fibers θ = 0 deg, 45 deg, and 90 deg. The obtained dependencies of the principal frequency variation of flexural vibrations on the relative notch location (Fig. 5) demonstrate the following. Firstly, independent of the fibers ’ orientation the maximum reduction of the principal vibration frequency is with the damage in the vicinity of the beam clamped end. With its shift to the beam free end, the principal frequency variation values Δ p d of flexural vibrations converge and at C x = 0.8 they are similar for different angle of the fibers. Here the largest damage effect on the obtained dependencies is observed at θ = 90 deg, whereas the smallest damage effect – at θ = 45 deg.

Fig. 5. Dependencies of the principal frequency variation Δ p d of flexural vibrations of the damaged beam ( а = 0.2) on C x at θ = 0 deg (1); 45 deg (2) and 90 deg (3).