Experimental and Numerical Evaluation of the Fundamental Natural ‎Frequency of a Spherical Core Sandwich Structure.‎

Abstract

Background:

This study investigates the effect of the variation of the geometrical factors on the fundamental natural frequency of the novel spherical core sandwich structure numerically and experimentally.  These novel structure are made up by using carving wax. The geometrical factors are diameter of sphere, skin thickness and spacing between spheres.

Materials and Methods:

Fifteen specimens according to response surface methodology - design of experiments  and using Box-Behnken method were manufactured from unsaturated polyester material with different geometry while maintaining a 20 cm effective length. The fundamental natural frequency was evaluated according to two methods numerically by using finite element analysis and experimentally by using the modal test. ANOVA statistical analysis was used to evaluate the effect of the geometrical factors on the natural frequency

Results:

The results show that the discrepancy between these methods was less than 15%. The spacing between the spheres was a dominant factor that influence the fundamental natural frequency. The sphere diameter is a less dominant factor while the skin thickness has a minor influence on the fundamental natural frequency of the spherical core sandwich structure.

Conclusions:

This study provides a better understanding of the influence of the geometrical properties of the structure on the fundamental natural frequency. The most influential factor on the fundamental natural frequency is the spacing between the spheres while The diameter of the sphere has less influence, while the skin thickness has a minor effect on the fundamental natural frequency.