| Sandwich structural damping composite material, with viscoelastic dampingmaterials as its damping layer, and fiber-reinforced resin composite material as itsstructural layer, possesses dual function of damping and bearing.It plays a veryimportant role in suppressing unwanted vibration, improving the mechanical stabilityof the device operation, reducing or eliminating noise pollution, and improvingpeople’s living and producting environment.In order to achieve damping-structural integration,3-D spacer fabric sandwichstructure was used in the thesis. As the two layers were connected by the continuousfiber columns, the composite had excellent performance of resistanting surface/corestripping which was common in traditional sandwich structure and mechanicalproperties (especially the Z-direction) had been significantly improved. This thesisfocused on the development of core material with high damping capacity,preparation of sandwich structure and optimization of sandwich structure.Firstly, a series of damping materials were prepared with different dampingproperties, and the factors affecting the performance of the damping layers werediscussed. In the blend system of alicyclic epoxy CER-170and bisphenol A epoxyresin CYD-128, D400was used as curing agent. By adjusting the ratio ofcomponents, when the alicyclic epoxy: bisphenol A epoxy=2:8, the damping of thematerial achieved its best performance: loss factor tanδmax=0.96，tanδ25℃=0.91.Andeffective damping temperature range of this system was around room temperature. Inthe blend system of FU and EP, when the FU: EP is3:7, the damping of the material achieved its best performance: tanδmax=0.93, and this system was conducive toforming. Based on this, the hollow glass beads (HGB) were introduced, to formHGB/(3FU-7EP) system. As HGB content increased, tanδ25℃of the core materialimproved firstly, and then decreased: the tanδ25℃of core material reached themaximum when the HGB amount was4wt.%.A series of3-D spacer fabric sandwich structures were prepared with damping materials as core materials. Firstly, the hollow3-D spacer fabric sandwich structurecomposite was prepared with3-D spacer fabric as its reinforcement. Then the premixof core material was filled into the hollow structure and formed to be the corematerial after the premix cured and then a new damping-structural integratedsandwich structural composite was produced. The loss factor η and damping ratio Dof sandwich structure were characterized by INV damping meter method and themechanical characteristics of sandwich structures were investigated at the same time.The effect of3-D sandwich structure, the types of core material, the HGB content ofcore material and core thickness on the performance of the sandwich structure wasdiscussed.3-D spacer fabric sandwich structure’s damping performance was slightlyworse but the flexural strength and impact toughness were significantly higher thantraditional sandwich structure connected skin and core material together by glue.Improving core material loss factor can significantly improve the damping propertiesof the sandwich structure. When the core material was alicyclic epoxy: bisphenol Aepoxy=2:8, the damping property of the sandwich structure was at its best: ηreached0.201, D reached10.17%. With the increase of HGB content,η and D ofsandwich structure improved firstly, and then decreased. The damping property ofthe sandwich structure was at its best when the HGB amount was4wt.%: η reached0.138,D reached6.90%. With the increase of the thickness of the damping layer, thedamping performance of sandwich structure improved significantly but the bendingstrength dropped dramatically.The optimization of3-D spacer fabric sandwich structure was achieved. Multi-sandwich structural composite materials were designed and the effect of placementorder on the performance of the multi-sandwich structure was discussed. To solvethe disadvantage of3-D spacer fabric sandwich structure, whose thickness ofstructural layer is thin, the structural layer was reinforced by fiber-reinforcedcomposites to achieve the balance of mechanical properties and damping properties. |
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