Free vibration, displacement and stress analysis of simply supported sandwich beam

In this study, the free vibration of a simply supported sandwich beam was investigated using the finite element method. The core layer of the beam is made of an isotropic material, while the top and bottom surfaces consist of carbon nanotube-added and carbon fiber-reinforced composite layers. The finite element modeling of the composite sandwich beam is based on Euler-Bernoulli beam theory. The Halpin-Tsai model was used to model the carbon nanotube-added fiber-reinforced composite layers on the upper and lower surfaces. The stress between the layer surfaces, natural frequency, and displacement values were computed using a MATLAB code developed based on the finite element method. In this study, the effects of the carbon nanotube ratio, fiber orientation angle, and core-height to beam-height ratio (h/H) on natural frequency, displacement, and stress values were investigated. For the investigated beam designs, the largest increase in the first natural frequency at 0o was 71.88%, while the largest decrease was 57.22% at 70o. The largest displacement increase was 720% at 70o, whereas the smallest displacement decrease was 49.2% for h/H=0.25. The largest stress increase was 26.53% at 0o, while the smallest stress decrease was 77.65% at 70o for h/H=0.75. For the beam with h/H=0.25 and porosity=0, the largest increase in the first natural frequency at 70o was 55.8%, the smallest displacement decrease was 62.5%, and the smallest core layer stress decrease was 62.14% for Vnt=0.5. For the beam with h/H=0.25 and Vnt=0, the smallest decrease in the first natural frequency at 70o was 3.25%, the largest displacement increase was 8.86%, and the smallest core layer stress decrease was 46.58% for porosity=0.5. It was observed that the investigated parameters significantly affect the natural frequency, displacement, and stress values.