Vibration Response of 3-D Space Accessible Sandwich Composite

A 3-D sandwich composite comprising of E-glass core piles which are woven to the facesheets is considered in this work. This arrangement creates interstitial spaces in the core which can be used for foam infusion for sound/vibration damping, fluid storage, or for routing wires or inserts, in addition to providing strength. The vibroacoustic response of such multi-functional materials has received little attention and is an important issue when the structure witnesses mechanical vibrations. This article presents the vibration related studies carried out on the 3-D sandwich composite, infused with SC-15 resin. The frequency response function (FRF) and the damping ratios are the parameters of interest for this study. In this study the experimental data is presented for the unfoamed (as received) core configuration and the core filled with the polyurethane (PUR) foam. The average damping ratio of the unfoamed sandwich panel was found to be 0.55%. An increase of 150% in the damping ratio was observed for the PUR foam filled panels for a 77% increase in weight when compared to an unfoamed sandwich panel. Use of vibration as a non-destructive damage detection technique is demonstrated for beam specimens damaged by flexural loading. A reduction of 35% in the resonant frequency and 193% increase in the damping ratio was observed for approximately 6% core damage of the sandwich composite.