Application Of Time-temperature Superposition Principle Research Articles

Viscoelastic model for analysing the behaviour of adhesive-bonded FRP-to-steel joints in civil engineering applications

Adhesively bonding fibre reinforced polymer (FRP) plates have been a mainstream method for strengthening civil engineering structures. The effectiveness of bonding strengthening is dependent on the performance of the adhesive layer. This study examines the time-temperature dependent viscoelasticity of a typical structural epoxy adhesive and develops a linear viscoelastic material model that can be used for numerical analysis. An accelerated test method involving dynamic mechanical analysis (DMA) and time-temperature superposition principle (TTSP) were used to characterise the structural adhesive. The corresponding limitations of this method were discussed, including decomposition effect, nonlinear viscoelasticity, applicability of TTSP, and further curing of the sample. The numerical study of the long-term behaviour of the single lap-shear FRP-to-steel joint found that a slightly warmer temperature (30 °C for this study) is beneficial for the bonded joint as it can reduce the concentrated shear stress with negligible increase in the shear strain. However, a higher temperature (50 °C for this study) that near the adhesive’s glass transition temperature (Tg) could be detrimental as it can lead to significant shear strain in the adhesive joint within the first year of service life.

Flexural creep behavior of hierarchical bamboo structure using time-temperature-stress superposition principle

The long-term flexural creep properties of graded hierarchical bamboo are important to structural design in civil construction. The present study conducted the short-term flexural creep tests at a series of temperature (30–170 °C) and stress (7–15 MPa) conditions, for the bamboo from both inner and outer parts. The application of time-temperature superposition principle (TTSP) and time-temperature-stress superposition principle (TTSSP) was analyzed for the creep behavior of bamboo with regard to hierarchical structure. The results confirmed the feasibility of TTSP and TTSSP in flexural creep of bamboo by horizontal shifting. A creep model based on Findley power law was successfully employed to predict the flexural creep response of bamboo. Additionally, the sample from inner part of bamboo displayed a more pronounced flexible creep response compared with the sample from outer part, attributing a low fiber volume fraction in inner part due to bamboo growth strategy. The findings in this study broaden the knowledge of bamboo rheology, and is helpful for further work on the bamboo growth strategy effect on mechanical properties.

Application of time-temperature superposition principle to pull-off tensile strength of asphalt tack coats

Flexible pavements are multilayered structures that are designed to withstand vehicular traffic and thermal loading. Tack coat provides the bonding between these multilayers, which is a critical mechanism to provide a pavement with the monolithic action of asphalt layers to resist traffic and thermal loading, thereby dictating the pavement’s service life. Asphalt binder bond strength (BBS) is an indicator that can be used to evaluate the interlayer bonding ability of tack coat and changes as a function of temperature and loading rate. The focus of this paper is to prove that the time-temperature superposition principle is applicable to the BBS of various tack coat materials. In order to achieve this goal, BBS and dynamic shear rheometer (DSR) tests were conducted on four different tack coats, CRS-2, CRS-1h, NTCRS-1hM, and Ultrafuse. The Pneumatic Adhesion Tensile Testing Instrument (PATTI) was used to determine the BBS at 13 different temperatures ranging from 5 °C to 53 °C. The BBS data showed that adhesive failures between the binder and pull stub of PATTI caused the drop of BBS below 5 °C to 15 °C for hard (CRS-1h) and Non-tracking (NTCRS-1hM, Ultrafuse) tack coat. In addition to the BBS test, DSR tests were performed on the emulsion residue to measure the time-temperature shift factors at the reference temperature of 20 °C. It was found that the time-temperature shift factors determined from the DSR tests could be successfully used to shift the BBS vs. stress rate curves to construct the mastercurve for all four tack coat materials at a residual application rate of 0.14 L/m2 (0.03 Gal/yd2) as long as the BBS test exhibited cohesive failure between the binder and pull-off stubs. A simple method based on the BBS values at two temperatures is proposed to predict the mastercurve for routine characterization of the BBS mastercurve. No definite trend in the BBS mastercurve emerged among the different tack coat application rates for the different tack coats.

Large strain/time dependent mechanical behaviour of PMMAs of different chain architectures. Application of time-temperature superposition principle

The relevance of equivalent strain rate at reference temperature derived from time/temperature superposition principle is validated as a constitutive parameter at large strain for PMMAs of different chain architecture. Shift factors were obtained from DMTA at infinitesimal strain, then identified according to Williams-Landel-Ferry or Arrhenius equations and finally extended to large deformations. Mechanical behaviour was characterized under cyclic tensile loading. So-called 3D digital image correlation was used to measure local strain. It is demonstrated that for different experimental conditions having same equivalent strain rate, the macroscopic behaviour will be the same. This was validated for elastoplastic, viscoelastic and rubbery behaviours. Such experimental observations indicate that time/temperature superposition at low strain can be extended for large deformation for PMMA. Additionally, the study opens a new way of addressing the temperature and strain rate dependencies in constitutive model by using the equivalent strain rate at reference temperature as a unique parameter.

Thermo-Mechanical Properties of Soft Candy: Application of Time-Temperature Superposition to Mimic Response at High Deformation Rates

Soft candy primarily consists of an amorphous sugar matrix with highly adhesive and cohesive characteristics, which is generated by rapid cooling of a supersaturated sugar solution. The integration of fondant in soft candy leads to a partial recrystallization of the amorphous sugar so that the dispersed sugar crystals disrupt the continuous amorphous phase; this lowers cohesiveness, and creates a short texture that is responsible for a more brittle fracture. Final processing (e.g., cutting and packaging) is usually done at temperatures between 25 and 45 °C and short time scale. This study analyzed the effects of temperature and time scale on thermo-mechanical properties of different types of soft candy. The application of time-temperature superposition principle on small amplitude oscillatory shear experiments resulted in master curves that covered a frequency window up to 105 rad/s, hence a time scale that is relevant in rapid processing. The respective shift factors depend on material properties, and a main factor of influence is the presence of a crystalline phase. Simple penetration and tensile tests give additional information on material behavior, especially with respect to effects of temperature on adhesiveness and cohesiveness. The results of the study provide support for further optimizing soft candy formulations to ensure rapid and undisturbed processing.

Viscoelastic properties of kenaf reinforced unsaturated polyester composites

In order to quantify the effect of temperature on the mechanical and dynamic properties of kenaf fiber unsaturated polyester composites, formulations containing 10 wt.% to 40 wt.% kenaf fiber were produced and tested at two representative temperatures of 30°C and 50°C. Dynamic mechanical analysis was performed, to obtain the strain and creep compliance for kenaf composites at various styrene concentrations. It is possible to obtain creep curves at different temperature levels which can be shifted along the time axis to generate a single curve known as a master curve. This technique is known as the time–temperature superposition principle. Shift factors conformed to a William–Landel–Ferry (WLF) equation. However, more long term creep data was needed in order to further validate the applicability of time-temperature superposition principle (TTSP) to this material. The primary creep strain model was fitted to 60 min creep data. The resulting equation was then extrapolated to 5.5 days; the creep strain model of power-law was successfully used to predict the long-term creep behavior of natural fiber/thermoset composites.

시간-온도 중첩이론을 적용한 아스팔트 바인더의 점소성 구성 모형

PURPOSES: Suggestion of asphalt binder constitutive model based on time-temperature superposition principle and overstress concept in order to describe behavior of asphalt binders. METHODS: A series of temperature sweep tests and multiple stress creep and recovery(MSCR) tests are performed to verify the applicability of time-temperature superposition principle(t-Ts) and to develop viscoelastoplastic constitutive equation based on overstress concept. For the tests, temperature sweep tests at various high temperature and various frequency and MSCR test at <TEX>$58^{\circ}C$</TEX>, <TEX>$64^{\circ}C$</TEX> <TEX>$70^{\circ}C$</TEX>, <TEX>$76^{\circ}C$</TEX>, and <TEX>$82^{\circ}C$</TEX> are performed. From the temperature sweep tests, dynamic shear modulus mastercurve and time-temperature shift function are built and the shift function and MSCR at <TEX>$58^{\circ}C$</TEX> are utilized to determine model coefficients of VBO model. RESULTS: It is observed that the time-temperature shift function built at low strain level of 0.1% is applicable not only to 1.0% strain level temperature sweep test but also maximum 500,00% strain level of MSCR test. As well, the modified VBO model shows perfect prediction on MSCR measured strain at the other temperatures. CONCLUSIONS: The Time-temperature superposition principle stands hold from very low strain level to very high strain level and that the modified VBO model can be applicable for various range of strain and temperature region to predict elastic, viscoelastic, and viscoplastic strain of asphalt binders.

インデンテーション法による粘弾性特性の評価と時間-温度換算則の適用

インデンテーション法による粘弾性特性の評価と時間-温度換算則の適用

OS1209 インデンテーション法による粘弾性特性の評価と時間-温度換算則の適用(ナノ・マイクロからの視点からの変形と破壊の力学(2),オーガナイズドセッション)

OS1209 インデンテーション法による粘弾性特性の評価と時間-温度換算則の適用(ナノ・マイクロからの視点からの変形と破壊の力学(2),オーガナイズドセッション)

Application of Time-temperature Superposition Principle on Cell Density of Foamed Plastics

Application of Time-temperature Superposition Principle on Cell Density of Foamed Plastics

On Interconversion of Various Material Functions of PMMA

The interconversion between various linear viscoelastic functions forPoly (methyl) methacrylate (PMMA) is explored. With the availability offour time or frequency-dependent material functions (shear, bulk,uniaxial and Poisson) on the same material, various material functionsare computed using the correspondence principle of the linearized theoryof viscoelasticity through the use of standard relations. Computedmaterial functions are evaluated against the directly measuredproperties and the limitations imposed on successful interconversion dueto the experimental errors in the underlying physical data are explored.It is observed that the differences between the computed and measuredfunctions were larger than suggested by experimental error. The resultsintimates the need to thoroughly re-examine the applicability oftime-temperature superposition principle often employed to develop`master curves' for viscoelastic functions, especially with respect tothe glassy domain.

マウスガードの化学構造と動的粘弾性

The chemical structures and dynamic viscoelastic properties of the proprietary mouth-formed and custom-made mouthguards used in contact sports were investigated to evaluate shock absorption and moldability.The infrared spectra of the molecular structure of each material were identified as ethylene-vinyl acetate copolymer (EVA). The contents of vinyl acetate in EVA were 27-39 mass%. The weight average molecular weights measured by the gel permeation chromatography were 99, 000-150, 000.The master curves of storage modulus G′, dynamic viscosity η′ and loss tangent tanδat the reference temperature of 35°C were constructed from the data obtained at different temperatures, by the application of time-temperature superposition principle. By this method, it is possible to evaluate the viscoelastic properties expanded to both higher and lower frequencies than can be obtained experimentally.The difference of G′ and tanδfor each material was due to the vinyl acetate content and molecular weight in EVA. Marked effects of the molecular weight on the master curves of tanδwere observed in a lowfrequency range: the lower the molecular weight, the higher the tanδ.It was suggested that the shock absorption and moldability of mouthguards could be evaluated from the master curve of tanδ.

結晶性高分子における張力-温度特性の粘弾性的意義

Equations describing force-temperature characteristics at constant length with constant rate of cooling are derived in two ways from the theory of linear viscoelasticity.The first method based upon the relaxation time spectrum and the time-temperature superposition principle gives Eq. (8). Secondly, Eq. (9) is deduced from the approximate consideration that the stress relaxation due to the contraction of original length with descending temperature is estimated by step-wise cooling approximation and use of relaxation modulus corresponding to the time of each step.Force-temperature measurement and its analysis are conducted on unoriented crystalline polyethylene terephthalate.The first and the second theoretical deductions are successfully applied to these results as shown in Figs. (3) and (4). While verifications of the first method are confined to the temperature range only above the second-order transition temperature (95°C, Fig. (1)) due to the limitation of the applicability of time-temperature superposition principle, those of the second method are done over the whole temperature range of measurements.