A Computerized Experimental Rig for the Vibration Investigation of Cracked Composite Materials Plate Structures

A composite plate is strengthened by reinforcements in the form of powder particles and short or long fibers, where the fiber glass was used as the reinforcement fiber to modify the composite plate was investigated. The crack effects on the plate natural frequencies were analyzed using different boundary conditions (SSSS, SSCC, SSFF). The problem was solved numerically using the Finite Element Method, adopting the ANSYS program, experimentally employing the time variation and measuring the natural frequency. The comparison between the finite element method and the experimental program has shown good agreement with a maximum discrepancy of not more than 8.5% for the tested cases of the composite plates. It was noticed that the natural frequency decreases with the presence of the crack. It was also noticed that the central damage effect has a higher effect on the natural frequency than the other crack positions. Also, the results show that the natural frequency decreases as the crack length or depth increases due to the stiffness reduction in cracked samples. And the increase in the aspect ratio of the plate means an increase in the mass of the plate, which results in a decrease in the natural frequencies. In addition, the results indicate a reduction in the natural frequency for the SSCC boundary condition was less than the decrease in the natural frequency for other boundary conditions, SSSS and SSFF. Finally, the results showed that the short fiber types modify the natural frequency more than the natural frequency of other reinforcement fiber types.