Analysis Of Dynamic Mechanical Analysis

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The viscoelastic behavior of bucky paper reinforced epoxy laminar composite materials for structural application has been evaluated through Dynamic Mechanical Analysis. The effects of heating rate, sinusoidal forces on glass transition temperature Tgwere studied. In DMA LVDT controlled sinusoidal force is applied and measures the response of the input as shown in the figure 3. It measures parameters which are the signature properties of the material under supervision like storage modulus, loss modulus, tanδ which are helpful to predict the behavior of the material in varying forces and temperature.
The stress applied as a function of time at a given frequency, ω, is given as σ(t)=σ_0 sin⁡〖(ωt+δ)〗

From Hook’s law, input stress and response
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The storage modulus, (E՛) is proportional to the energy stored per cycle, the loss modulus; (E″) is proportional to the lost or dissipated energy per cycle. The storage modulus characterizes the elastic behavior of the material, and the loss modulus characterizes the viscous behavior of the material. The ratio of energy dissipated to energy stored is the tangent of the phase angle, δ, called tanδ, which is given by tan⁡δ=(E^" (ω))/(E^' (ω))
In this study oxidized refluxed CNT bucky paper impregnated in epoxy laminar composites were used and the behavior after post curing was also studied with the use of DMA.
4.3.1 Storage
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Figure1 (b) shows the effect of post curing on different type of CNT bucky paper reinforced laminar composites. It depicts that the peak values of the loss modulus was shifted towards the maximum temperature in both the cases i.e 16ply and 16ply fun after post curing , which indicate the reduction of polymer chain mobility and increase in the internal friction. This was further supported by its crosslink density. The increased internal friction due to cross linking between CNT and epoxy enhances the dissipative effect. Therefore the intensities of the peak were also increased after post

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