Time Temperature Stress Superposition Research Articles

Flexural properties of surface reinforced wood/plastic deck board

AbstractDecking and railing is the largest and fastest growing market for wood–plastic composites (WPCs). Despite WPC's advantages in comparison to lumber, its modulus and creep resistance need to be further improved for demanding structural applications. In this study, WPC deck boards were reinforced by the composite sheets made of commingled glass and polypropylene fiber. Various reinforcement arrangements were carried out to identify the optimal one. Scanning electron microscopy revealed good bonding at the reinforcement/WPC interface. All reinforced samples exhibited considerably increased modulus of rupture, modulus of elasticity, and strain at break. The creep resistance of the reinforced WPC boards was also greatly improved. Creep strain was simulated with Findley's model. Master curves of creep compliance were generated by time–temperature–stress superposition principle. The Prony series was found to be the analytical expression of the master curves with acceptable accuracy. With improved mechanical properties, the reinforced WPC board can be used in more demanding applications. POLYM. ENG. SCI., 47:281–288, 2007. © 2007 Society of Plastics Engineers.

Effect of Stress-Induced Damage Evolution on Long-Term Creep Behavior of Nonlinear Viscoelastic Polymer

The mechanical behaviors were investigated by nonlinear creep tests of poly(methyl methacrylate) under different temperatures. The test duration was 4000 seconds. The corresponding temperature shift factors, stress shift factors and temperature-stress shift factors were obtained according to time-temperature superposition principle, the time-stress superposition principle and the time-temperature-stress superposition principle (TTSSP). The master creep compliance curve up to about 1-month at a reference temperature 22 degrees centigrade and a reference stress 14 MPa was constructed, and the effect of stress-induced damage evolution on the long-term creep behavior of polymeric material was accounted. It was shown that TTSSP provides an effective accelerated test technique in the laboratory, the results obtained from a short-term creep test of poly(methyl methacrylate) specimen at high temperature and stress level can be used to construct the master creep compliance curve for prediction of the long-term mechanical properties at relatively lower temperature and stress level, and the master creep compliance curve with damage considered can be applied to accurately characterize the long-term creep behavior of nonlinear viscoelastic polymer.

Scottish style and American romantic idiom

This paper presents an experimental and analytical study about the effect of temperature on the flexural creep of GFRP laminates produced by vacuum infusion. Such laminates are considered for use in the faces of sandwich panels for building floor application. Flexural creep tests were carried out in a three point bending configuration for stress levels of 15%, 25% and 35% of the laminate's flexural strength, and temperatures of 20 °C, 24 °C and 28 °C (a range likely to be found in the envisaged application), with durations between 1000 h and 2215 h. The creep response was observed to increase both with temperature and stress level. Findley's power law was used to model the experimental results, and extended to include an Arrhenius equation for temperature dependence of the creep response. The proposed model provided a good fit to the experimental creep curves, and was used to derive a set of practical design equations for the time-temperature dependent (i) flexural modulus, (ii) creep coefficient, and (iii) flexural modulus reduction factor. Finally, the time-temperature-stress superposition principle (TTSSP) and the time-stress superposition principle (TSSP) were used to obtain “master curves” that compared well with the proposed model's predictions.

Effects of temperature on the creep behaviour of woven and stitched composites

This paper presents an investigation of the tensile creep behaviour of woven fibre composite stitched, through the thickness, with cotton or carbon threads along the loading direction. Creep tests were conducted at various temperatures. It was found that the through-thickness stitching significantly improved the creep deformation and creep rupture resistance of these composites. The creep data were analysed using the ‘timetemperature-stress superposition principle’ theory (TTSSP). The long-term behaviour of the material could then be predicted by means of a master curve. Finite-element analyses of the composites was also carried out and the stitching was found to considerably reduce the interlaminar stresses.

Creep behavior of carbon-fiber-reinforced polyetheretherketone (PEEK) [ ±45]4s laminated composites (I)

The creep properties of AS-4/PEEK [ ± 45]4s laminated composites have been investigated. The temperature dependence of the viscoelastic behavior of the matrix composite and the bulk resin was studied by dynamic mechanical analysis. The tensile properties were measured at elevated temperature. The tensile failure morphology at elevated temperature was investigated by scanning electron microscopy. The accelerated characterization of the creep response due to the effect of temperature and stress was studied. Short-term creep tests were performed at various stress levels and at elevated temperatures. The creep strain data were fitted by using the Findley equation. It was found that results predicted by the Findley equation showed good agreement with the experimental data. Coupling with the Findley equation, a master curve was constructed by using the time-temperature-stress superposition principle (TTSSP) with a reference condition at 85°C and 94.38 MPa. From the short-term creep test obtained after 600 min, a smooth master curve was obtained by the proposed procedure of accelerated characterization and a creep strain of 106.29 min can be predicted.