Preparation And Properties Of Epoxy-Based Composites Containing Carbon Nanotubes And PMN-PZT As Rigid Piezo-Damping Materials

High vibrations can result in equipment damage and production accidents, and shorten the service life of materials. Owing to their quality to dissipate elastic strain energy when subjected to vibratory loads, Damping materials are extensively used in various fields such as vehicles, industrial machine and so on. Polymers, especially rubbers and rubber-based composites can be used as the damping materials for their viscoelasticity, but their narrow glass transition region and strong dependence on the temperature and frequency limited their practical applications, particularly as the structural materials.The new damping mechanism that Piezoelectric and conductive mechanism has caused the extensive concern. It can be described as follows: for some specialized composites, mechanical vibrating energy is first transmitted to the piezoelectric ceramic powders and converted into alternating electrical potential energy by the piezoelectric effect. And then, the electrical potential energy is further converted into Joule heat through the networks of electro conductive particles .In present work, we prepared a series of the epoxy-based composite materials containing multi-walled carbon nanotubes(CNTs) and piezoceramic complex of lead magnesium niobate and lead zirconate titanate(PMN-PZT) basing on the new damping mechanism. First, the raw materials were pretreated, and then electrical conductivity, dynamic mechanical properties, the morphology and so on of piezoelectric damping composites were studied.The influence of CNTs volume content on the electrical conductivity of the piezoelectric damping composites was researched. The results showed that the composites exhibited a percolation threshold in the range of 1-1.5 g CNTs per 100 g epoxy, and under this circumstance, a continuous electro-conductive network was formed. Meanwhile, the theoretical percolation threshold were predicted by the power law. It can be found that the predicted percolation threshold accords well with the experimental data. At the same time, the dependence of the dielectric constant on the PMN-PZT loadings was studied, which reveals that the main contribution to dielectric behavior comes from the high-dielectric ceramic phase in composites.The SEM images for the impact-fractured surface of the epoxy/CNTs/PMN-PZT composites were observed. A very good dispersion of the filler in matrix can be deduced from the pattern of the impact-fractured surfaces of these samples, and the conductive networks have been formed when the CNTs content reaches 1.2 g per 100 g epoxy.The dependence of the damping capacity on the PMN-PZT and CNTs loadings was researched. The results showed that the epoxy-based composites have a significant piezo-damping effect at the high PMN-PZT loading and CNTs loadings of above critical electrical percolation.The thermal and mechanical were studied. The results showed that the glass transition temperature and the mechanical properties were improved remarkably after incorporating these two fillers. Finally, thermodynamic stability and the mechanical properties were enhanced, which means this material can be got the extensive usage.The present work provided a useful route to design a good piezoelectric damping material, in which the PMN-PZT contributes to the transformation of mechanical noise and vibration energies into electric energy, while the CNTs serve in the shorting of the generated electric current to the external circuit. Based on this study, a new type of epoxy-based composites as the piezo-damping is designed.