Composition, Structure And Damping Property Of PMN/CNTs/EP Piezoelectric Damping Composite

To control the vibration and reduce noise, the damping materials convert the vibrational energy to thermal energy and this vibration and noise reduction technology has widely applied in the automotive, aviation and ships fileds. The damping materials like rubber have superior damping properties, but poor mechanical strength. Because of its excellent mechanical properties, epoxy resin, as a new generation of structural damping material, becomes a hot now. The damping performance of pure epoxy resin is not good enough; so much attention has been paid in adding piezoelectric and conductive particles, introducing multiple energy dissipation mechanism to the damping enhancement. However, multiple energy dissipation mechanisms and the proportion of various energy dissipation to the overall damping performance are not very clear. In this essay, PMN, carbon nanotubes (CNTs) and epoxy resin (EP) are used to fabricate the0-3PMN/CNTs/EP damping materials. And the damping percentage of piezoelectric and conductivity phase to the damping properties of the composites is studied in detail. Besides, the relationship between the resistivity and damping properties are built as well.Firstly, CNTs are taken as the conductivity phase and the effect of interfacial strength on the CNTs/EP damping materials is investigated. To acquire different interfacial strength (including van der Waals, weak and strong covalent bond) of CNTs enhanced polymers, different functionalizations of CNTs have been designed through acid treatment and silane termination. According to the study, strong interfacial covalent bond of CNTs/epoxy composites contributes to the CNTs dispersion in the matrix and the CNTs-Silane/EP has the best damping properties. To some extent, weak interfacial covalent bond leads to better dispersion and damping properties of CNTs-COOH/EP in comparison with the CNTs-Pristine/EP. Furthermore, the CNTs-COOH/EP shows superior conductivity properties and the silanzied functionlization has an adverse effect on conductivity because of the Si-O bond.So the CNTs with acid treatment are chosen to be the conductivity phase in the piezoelectric damping materials.Secondly, PMN are taken as the piezoelectric phase and the damping mechanism of PMN/EP damping materials is investigated. According to the study, when the PMN content is20wt.%, the maximum loss factor is0.559. When the PMN content is higher than60wt.%, the damping enhancement due to the interfacial friction dissipation is offset by the decreasing volume fraction of viscoelastic matrix. So20wt.%and60wt.%of PMN are chosen to apply in the piezoelectric damping materials.Finally, PMN and CNTs are taken as the piezoelectric phase and conductivity phase, respectively, and the mechanisms of the interfacial effect and piezoelectric effect in the PMN/CNTs/EP piezoelectric damping materials are studied. According to the study,20wt.%of PMN just contributes to the interfacial friction dissipation to the damping enhancement. And the interfacial effect is the dominant factor to influence the damping properties. The resistivity has nothing to do with the damping properties of the composites. The maximum value of loss factor is0.653. The fraction of interfacial effect between CNTs and matrix on the damping enhancement is about25.27%; the fraction of interfacial effect between PMN and matrix is10.41%; and the fraction of epoxy resin on the damping enhancement is nearly64.32%; Only when the resistivity of PMN/CNTs/EP composites containing60wt.%of PMN is10～108Ω·cm, can the piezoelectric effect contribute to the enhancement of damping properties. The maximum value of loss factor is0.683. Both the interfacial effect and piezoelectric effect are the important factors to influence the damping properties. The fraction of interfacial effect between CNTs and matrix on the damping enhancement is about16.25%;the fraction of interfacial effect between PMN and matrix is0%;and the fraction of epoxy resin on the damping enhancement is nearly61.49%;the fraction of piezoelectric effect is about22.25%. If the resistivity of the composite is lower or higher than10～10Ω·cm, the electrical energy converted by mechanical energy through piezoelectric effect may not effectively be dissipated electrical network, and then the interfacial effect is the dominant factor to the damping enhancement.