| With advantages such as high strength,low curing shrinkage,many kinds of bonding and excellent corrosion resistance,epoxy resin has been widely used in various aspects of practical engineering.Especially in civil engineering,epoxy resin adhesive have a good prospect for development in using as building repair adhesive to repair structural cracks.Many indexes of epoxy resin,including heat resistance and mechanical properties,will significantly affect the use of materials.Especially,it has typical viscoelastic properties,which cause the time related factors such as heating rate,loading frequency,aging time have a significant impact on the mechanical behavior of the material.Therefore,the study on the dynamic mechanical behavior of epoxy resin adhesives in their aging process is not only of theoretical significance,but also has a broad prospect of engineering application.This paper was supported by the science and technology project of Hunan Provincial Science&Technology Department(2010GK3110),the key projects of the science and technology plan of The Education Department Of Hunan Province(10A130)and the postgraduate innovation project of Central South Forestry University of Science and Technology.The main work and innovation points are summarized as follows:(1)A formula of epoxy resin adhesive was designed and prepared.The curing degree,tensile strength and DMA temperature spectrum were tested and analyzed to determine the strength and heat resistance of the adhesive.(2)A DMA 8000 dynamic thermal mechanical analyzer which protected by PerkinElmer Company of USA was used to measure the DMA frequency spectrum of the samples.The results showed that with the increase of temperature,the storage modulus under the same frequency tended to decrease.And if the values of the storage modulus under the same temperature were compared,the storage modulus increased with the increase of frequency.However,the loss modulus decreased with the increase of frequency or temperature.(3)According to the time-temperature equivalent theory,taking 50? as the reference temperature.The frequency-modulus test curve measured under the reference temperature did not move,and the frequency-modulus curve under other temperature levels moved horizontally,which made all the curves forming a main curve with the curve under 50?.After horizontal translation of the displacement factor,the relationship between the storage modulus and the frequency can be obtained under a wide frequency of 12 orders of magnitude(10-6?106Hz)under 50?.The curve was then fitted by the constitutive equations of Zener rheological models with integer order or different fractional orders respectively.The results showed that the fractional order rheological models could better describe the dynamic viscoelastic behavior of materials under wide frequency than the traditional integer order model,and the lower the fractional order,the better the fit.(4)The dynamic viscoelastic behavior of the self-made epoxy resin structural adhesive during thermal aging under 75 °C and 100? was studied by using the time-aging time equivalent principle.Using the principle of time-temperature equivalence,the experimental data under different aging times were amplified to a wide frequency for comparison.Because the shape of each curve was similar,the isometric relationship of dynamic viscoelasticity of the adhesive under different aging time was established by introducing the aging time displacement factor.The influence of aging temperature on the aging time displacement factor was also discussed.The calculation model of dynamic viscoelastic aging time displacement factor was obtained,which provides a reference frame for predicting the service life of adhesive. |
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