Preparation And Quantitative Analysis Of Damping Properties Of CNTs/PMN/EP Piezoelectric Damping Composites

Damping materials convert mechanical vibration energy to thermal energy for vibration and noise control,this type of vibration attenuation material is widely used in automotive and ships fields.In this dissertation,epoxy resin?EP?was chosen as polymer matrix,lead magnesium niobate-lead zirconate-lead titanate?PMN?and zirconium dioxide?ZrO₂?were used as ceramic phase,and carbon nanotubes?CNTs?were taken as conductive phase to fabricate 0-3 damping composites.Tan?area?TA?analysis method was selected to evaluate the damping properties which obviously clarified the effect of maximum loss factor?tan??and effective temperature range on damping properties,and damping percentage of each filler was quantitatively analyzed via the value of TA.Thus the synergy of piezoelectric and conductive phase was further researched.The synergistic mechanism of piezoelectric effect and interfacial effect can be further researched by replacing PMN with ZrO₂ ceramics without piezoelectric effect.Firstly,the dispersion of fillers in composites was investigated.CNTs uniformly dispersed in epoxy matrix as independent unit at 0.2wt.%CNTs content in CNTs/EP composites.With the content of CNTs increasing,the interparticle distance between carbon nanotubes was very close.CNTs started to entangle with each other when the content reaches 2.0wt.%.Ceramic phase dispersed well in PMN?ZrO₂?/EP composites when the content of ceramic filler less than 60wt.%.Secondly,damping enhancement effect of each filler was quantitatively analyzed.The damping enhancement of composites mainly included two methods:interfacial effect of conductive phase?CNTs?and ceramic phase?PMN,ZrO₂?with matrix produced frictional energy dissiation;synergies of conductive network formed by CNTs and piezoelectric effect of PMN introducing new damping mechanism to promote energy dissipation.The interfacial effect is the main energy dissipation method for two-phase composites.CNTs/EP composites showed high loss factor?0.563?and wide effective temperature range?30.9??,and damping percentage of CNTs reached 32.22%.TA value of PMN/EP composites and PMN damping percentage reached maximum 14.4 and 30.44%at 40wt.%PMN content.Piezoelectric effect of PMN can be separated through replacing PMN with ZrO₂ceramic,and the mechanism of damping enhancement was researched.Finally,the synergy of piezoelectric phase and conductive phase in CNTs/PMN/EP composites was quantitatively analyzed and the effect mechanism was researched,and the same goes for the synergy of piezoelectric effect and interfacial effect.The synergy of piezoelectric phase and conductive phase resulted in damping enhancement of piezoelectric effect.CNTs was the dominant factor of damping enhancement when the CNTs content less than 0.6wt.%,and the damping percentage was 29.14%.When the CNTs content reached percolation threshold,bound charge existed on the crystal surface was exported by conductive circuit formed by CNTs and PMN particles,and then dissipated as thermal energy.Thus PMN became the dominant factor of damping enhancement,and the maximum damping percentage reached 47.43%.Damping enhancement method of CNTs/PMN/EP piezoelectric damping materials mainly included two aspects:interfacial effect and piezoelectric effect.Interfacial effect was the dominant factor of damping enhancement when the CNTs content less than 0.2wt.%,and the damping percentage reached 23%.With the increasing of CNTs content,CNTs mainly participated in the damping enhancement of piezoelectric effect of PMN as conductive network structure,thus the interfacial effect enhancement was reduced.Piezoelectric effect became the dominant factor of damping enhancement,and the damping percentage reached 46.38%.