Study On The Viscoelastic Matereials And Dynamic Properties Of Viscoelastic Laminated Structure

Viscoelastic materials(VEM)and constrained layer damping structure(CLD)have been widely used in vibration control,especially in vessel,aerospace and machine manufacture industries.Basic properties of two kinds of viscoelastic materials(referred to as Qtech 501 and Qtech 413)have been studied in this paper.Dynamic damping performance was analyzed by dynamic mechanical analyzer(DMA),and the test data was accomplished by means of time-temperature superposition.The loss factors of the elastic support structure and the cantilever structure were calculated by hammer test.The influence of damping layer thickness,constrained layer thickness,constrained layer properties on loss factors and loss efficiencies have been studied.Firstly,the conventional properties of the two viscoelastic materials,including curing time,solid content,density and basic mechanical properties,were characterized.The solid content of Qtech 501 and Qtech 413 was 97.58% and 94.76%,respectively,which meant both of them belong to fast curing,high solid content,and environmentally friendly materials.The density of the two materials were respectively 1.140g/cm3 and 0.997g/cm3,indicated they would have small influence on the mass of structure.The results of hardness,tensile strength,and elongation at break shows that the mechanical behavior of the Qtech 501 is close to viscosity,while another is closer to the elasticity.The damping performance of Qtech 413 viscoelastic material has been analyzed by DMA,and the effects of temperature and frequency on the dynamic properties were investigated.When the frequency was constant,the storage modulus reduced,but the loss factor firstly increased and then decreased,and the peak loss factor existed in Tg with the temperature increased.When the temperature was invariable,higher frequencies resulted in the higher storage modulus,higher Tg and loss factor.The test data of DMA was accomplished by means of time-temperature superposition using Origin software.The Adj.R-Square and Residual sum of squares of storage modulus were 0.999 and 1.767,respectively,and 0.996 and 3.469×10-4 for loss factor.Vibration duration was mainly 0.14~0.18 s and the optimal thickness of the damping layer is 0.7mm for the elastic support structures.For the structure constrained by 1mm steel,the damping efficiency was highest when the damping layer was 0.5mm,however,for other structures were 0.3mm.It seems likely that thinner damping layer had better damping efficiency,and the CLD structure with the thinnest damping layer had the highest efficiency.When the constraining layer was aluminum,the loss efficiency was 4~8 times higher than the structure constrained by steel.The highest loss efficiency for constrained layer was 1mm aluminum,the values were 5.47%,7.02% and 7.48% for 0.3mm,0.5mm,0.7mm damping layer,respectively.The vibration level reduced with the thickness increasing of the constraining layer and the constrained layer.Vibration duration was also mainly 0.14~0.18 s for the cantilever structures.The optimal thickness of the damping layer was 0.7mm and 0.3mm for structures constrained by steel layer and aluminum layer,respectively.When the constraining layer were polypropylene(PP)and polymethyl methacrylate(PMMA),the optimal thickness of the damping layer were both 0.5mm.It seems likely that thinner damping layers would have better damping efficiency,and the laminated structure with the thinnest damping layer had the highest efficiency.The highest loss efficiency was 58.4% when the thickness of damping layer was 0.3mm and 2mm for aluminum constrained layer.For a particular constraining layer material,the laminated structure with the thinnest constraining layer had the highest efficiency.When the constrained layer were PP and PMMA,the loss factors and loss efficiencies were higher than CLD structures constrained by metal layer caused by material properties.When the constraining layer were steel,aluminum,PP and PMMA,the highest loss efficiencies were1.33%,6.49%,17.49% and 18.99%.The vibration level reduced with the thickness increasing of the constraining layer but not the constrained layer.It can be concluded that the modulus and stiffness of constraining layer should be matched with the base layer so as to increase shear deformation of damping layer.Moreover,the constraining layer should have higher material loss factor.The structure loss factor can be increased by the two methods to control vibration better.