Rapid Lifetime Evaluation of Hybrid Composite Rods by Creep Behavior

2013 ◽  
Vol 873 ◽  
pp. 373-378
Author(s):  
Feng Tao Lan ◽  
Ye Wen Cao ◽  
Ying Nan Wang ◽  
Xin Chen ◽  
Chong Zhang
Keyword(s):  
Hybrid Composite ◽  
Superposition Principle ◽  
Mechanical Analysis ◽  
Widespread Application ◽  
Accelerated Creep ◽  
Different Temperatures ◽  
Time Temperature Superposition Principle ◽  
Term Creep ◽  
Short Term Creep

Hybrid composite rods, comprised of unidirectional reinforcing carbon/glass-fiber and adhesive epoxy matrix, are viewed as promising candidates to be used in high-voltage overhead conductors. However, before widespread application, their long-term durability needs to be clarified. In this study, accelerated creep testing for hybrid composite rods, is presented by taking dynamic mechanical analysis tests at different temperatures. Using the time-temperature superposition principle and thermal activation energy theory, the short-term creep data are combined to generate creep long-term compliance master curves. Through the master curve, predictions can be made concerning the creep levels that will occur during the design lifetime of hybrid composite rods (i.e., 30 years). It is found that after 30-year service at 120 °C, fully-cured hybrid composite rods only exhibit a slight increase in compliance (about 5%), indicating a satisfactory creep resistance at this temperature.

Effects of moisture content and temperature on wood creep

Holzforschung ◽  
2018 ◽  
Vol 72 (12) ◽  
pp. 1071-1078 ◽  
Author(s):  
Tai-Yun Hsieh ◽  
Feng-Cheng Chang
Keyword(s):  
Moisture Content ◽  
Creep Strain ◽  
Superposition Principle ◽  
Japanese Cedar ◽  
Creep Tests ◽  
Instantaneous Strain ◽  
Proposed Model ◽  
Time Temperature Superposition Principle ◽  
Term Creep ◽  
Short Term Creep

AbstractThe effects of moisture content (MC) and temperature (T) on the creep of Japanese cedar were investigated via a series of short-term creep tests, while MC had a higher effect than T, desorption of water caused more deformation. The results were separated into two distinct groups with MCs higher or lower than the equilibrium moisture content (EMC) and it was found that the mechano-sorptive effect is time-independent. The total creep strain of wood was explained by a model considering the instantaneous strain, creep strain and strain induced by the mechano-sorptive effect. The proposed model is in agreement with the creep master curves based on the time-temperature superposition principle (tTSP).

Viscoelastic properties of kenaf reinforced unsaturated polyester composites

2014 ◽  
Vol 03 (01) ◽  
pp. 1450004 ◽  
Author(s):  
Ekhlas A. Osman ◽  
Saad A. Mutasher
Keyword(s):  
Unsaturated Polyester ◽  
Superposition Principle ◽  
Creep Data ◽  
Kenaf Fiber ◽  
Temperature Superposition ◽  
Polyester Composites ◽  
Time Temperature Superposition Principle ◽  
Term Creep ◽  
Strain Model

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.

scholarly journals Assessment of Long Term Creep Using Strain Rate Matching From the Stepped Isostress Method

2019 ◽  
Author(s):  
Robert Mach ◽  
Jacob Pellicotte ◽  
Amanda Haynes ◽  
Calvin Stewart
Keyword(s):  
Creep Strain ◽  
Superposition Principle ◽  
Time Shift ◽  
Projection Model ◽  
New Approach ◽  
Matlab Code ◽  
Accelerated Creep ◽  
Term Creep ◽  
Calibration Approach

Abstract Creep testing is an ongoing need, particularly with the development of new candidate alloy systems for advanced energy systems. The conventional creep test (CT) is regarded as a proven method to gather creep data however, the test is impractical due to being real-time: lasting up to 105 hours to characterize the service of long-lived turbomachinery components. Accelerated methods to gather the long-term creep properties of materials are needed to reduce the time to qualification of new materials. The time-temperature-stress-superposition principle (TTSSP) and the derivative time-temperature superposition principle (TTSP), time-stress superposition principle (TSSP), stepped isothermal method (SIM), and stepped isostress method (SSM) are accelerated creep tests (ACT) commonly used to predict the long-term creep behaviors of polymers and composites. The TTSP and TSSP tests require multiple specimen tested at various temperatures/stresses whereas the SIM and SSM tests employ a single specimen where temperature/stress are periodically step increased until rupture. The stepped creep deformation curve can then be time and strain shifted to produce a master creep curve. While these ACTs are useful tools to predict long-term creep, the drawback is the lack of mathematical laws to determine the virtual start time and time shift factors, especially for different materials. In this paper, a new self-calibration approach is developed and compared to existing SSM data for Kevlar 49. This new approach focuses on matching the creep strain rates between stress steps and fitting the data to a master curve using a modified theta projection model. This is performed using a MATLAB code consisting of five subroutines. The first subroutine takes the stress, time, and creep strain from SSM/SIM tests, and segregates the data intro arrays corresponding to each stress level. The second subroutine finds the constants for the modified theta projection model for each stress level. The third subroutine performs a time shift adjustment using creep strain rate matching. The fourth subroutine calculates the accelerated time of rupture. The last subroutine generates accelerated creep versus time plots. Kevlar 49 SSM data is gathered from literature and run through the MATLAB code. The master curves generated from the MATLAB are compared to the conventional creep curve of Kevlar 49 as well as the master curve gathered from literature in order to validate the feasibility of this new approach. The goal of this project is to vet if the self-calibration approach can produce results similar to the reference calibration approach.

scholarly journals Time–Temperature–Plasticization Superposition Principle: Predicting Creep of a Plasticized Epoxy

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1848 ◽  
Author(s):  
Andrey E. Krauklis ◽  
Anton G. Akulichev ◽  
Abedin I. Gagani ◽  
Andreas T. Echtermeyer
Keyword(s):  
Glass Transition ◽  
Creep Behavior ◽  
Superposition Principle ◽  
Matrix Material ◽  
Epoxy Compound ◽  
Polymer Materials ◽  
Short Term ◽  
Term Creep ◽  
Short Term Creep

Long-term creep properties and the effect of water are important for fiber reinforced polymer (FRP) composite materials used in offshore applications. Epoxies are often used as a matrix material in such composites. A typical design lifetime of offshore FRP structures is 25 or more years in direct contact with water leading to some deterioration of the material properties. Knowing and predicting the extent of the material property deterioration in water is of great interest for designers and users of the offshore FRP structures. It has been established that the time–temperature superposition principle (TTSP) is a useful tool for estimating changes in properties of polymer materials at long times or extreme temperatures. In this work, a time–temperature–plasticization superposition principle (TTPSP) is described and used for predicting the long-term creep behavior of an epoxy compound. The studied epoxy does not degrade chemically via hydrolysis or chain scission but is negatively affected by plasticization with water. The methodology enables prediction of the long-term viscoelastic behavior of amorphous polymers at temperatures below the glass transition (Tg) using short-term creep experimental data. The results also indicate that it is possible to estimate the creep behavior of the plasticized polymer based on the short-term creep data of the respective dry material and the difference between Tg values of dry polymer and plasticized polymer. The methodology is useful for accelerated testing and for predicting the time-dependent mechanical properties of a plasticized polymer below the glass transition temperature.

Prediction of Long Term Stress Rupture Data for 2124

2006 ◽  
Vol 519-521 ◽  
pp. 1041-1046 ◽  
Author(s):  
Brian Wilshire ◽  
H. Burt ◽  
N.P. Lavery
Keyword(s):  
Q Methodology ◽  
Fracture Behavior ◽  
Stress Rupture ◽  
Creep Data ◽  
Short Term ◽  
Rupture Data ◽  
Term Creep ◽  
Term Data ◽  
Short Term Creep

The standard power law approaches widely used to describe creep and creep fracture behavior have not led to theories capable of predicting long-term data. Similarly, traditional parametric methods for property rationalization also have limited predictive capabilities. In contrast, quantifying the shapes of short-term creep curves using the q methodology introduces several physically-meaningful procedures for creep data rationalization and prediction, which allow straightforward estimation of the 100,000 hour stress rupture values for the aluminum alloy, 2124.

Short-Term Creep Data Based Long-Term Creep Life Predictability for Grade 92 Steels and Its Microstructural Basis

2018 ◽  
Vol 25 (3) ◽  
pp. 713-722 ◽  
Author(s):  
Seen Chan Kim ◽  
Jae-Hyeok Shim ◽  
Woo-Sang Jung ◽  
Yoon Suk Choi
Keyword(s):  
Creep Data ◽  
Creep Life ◽  
Short Term ◽  
Term Creep ◽  
Short Term Creep
Sign in / Sign up

Export Citation Format

Share Document