The effect of carbon nanotube dispersion on the dynamic characteristics of unidirectional hybrid composites: An experimental approach

An experimental study on the natural frequencies and damping properties of hybrid composite beams and plates are presented in this paper. Hybrid composites consist of a matrix material along with both nano-fillers and micro fibers. In this research, carbon nanotube (CNT) is used as nano-filler. Epoxy, CNT/epoxy, glass/epoxy, CNT/glass/epoxy, carbon/epoxy and CNT/carbon/epoxy beam-shaped specimens are fabricated. Free vibration analysis of cantilever beams is examined in order to characterize the dynamic behavior of the specimens. 9.4% increase in the fundamental frequency and 12.3% decrease in the damping ratio of the CNT/glass/epoxy beam are observed with respect to those of the glass/epoxy beam specimen. Further, it is observed that CNT/carbon/epoxy beam has degraded fundamental frequency (13.9%) and enhanced damping ratio (31.5%) in comparison with those of carbon/epoxy beam specimen. Moreover, the first bending natural frequencies of the glass/epoxy, CNT/glass/epoxy, carbon/epoxy and CNT/carbon/epoxy plates are obtained experimentally. Plates with all free edges (FFFF) and plates with one edge clamped (CFFF) are investigated. Finite element models confirm the results obtained. Furthermore, the effects of the interfacial adhesion between the CNT/epoxy matrix and micro fibers on the damping properties of the laminated composites are discussed using the obtained results and the scanning electron microscopy (SEM) images.