Modal Analysis of Specific Composite Sandwich Structures

Abstract

Composite sandwich structures are gaining attention due to their inherent properties, such as lightweight, low density, and high strength. The forced vibration response of these structures was studied experimentally to investigate the effects of external loads on these structures. In this work, four composite sandwich structures were manufactured using carbon fiber, glass fibers, and foam and tested on a specially designed vibration test rig by hitting the specimen with an impact hammer. The response was recorded by an accelerometer attached to the specimens. The accelerometer signal was amplified, and the input and output signals were transferred to LABVIEW via a data acquisition card and were processed in MATLAB. The impact hammer acts as an external excitation source, and the frequency response function was found for each specimen under various edge boundary conditions. Bode plots were plotted for each test, and the peak frequency and the phase difference were compared. It was found that composite sandwich specimens made of carbon fiber skins and carbon fiber honeycomb core showed a higher frequency response among all specimens (400 Hz). Furthermore, it was found that the foam core layer reduces the phase difference between the input and output signals from (360degrees) to (180degrees) compared with other honeycomb cores. Therefore, the procedure outlined in this research can be applied to other structures to investigate their vibration response. In addition, this work could be beneficial for the diagnosis of structure stability using a forced vibration response procedure.

Keywords

• composite sandwich
• sandwich manufacturing
• forced vibration
• modal analysis
• frequency response function