Effect of Cure State on Stress Relaxation in 3501-6 Epoxy Resin

1997 ◽  
Vol 119 (3) ◽  
pp. 262-265 ◽  
Author(s):  
S. R. White ◽  
A. B. Hartman
Keyword(s):  
Stress Relaxation ◽  
Epoxy Resin ◽  
Creep Compliance ◽  
Numerical Technique ◽  
Matrix Material ◽  
Relaxation Modulus ◽  
Master Curves ◽  
Creep Tests ◽  
Three Point Bending ◽  
Direct Inversion

Little experimental work has been done to characterize how the viscoelastic properties of composite material matrix resins develop during cure. In this paper, the results of a series of creep tests carried out on 3501–6 epoxy resin, a common epoxy matrix material for graphite/epoxy composites, at several different cure states is reported. Beam specimens were isothermally cured at increasing cure temperatures to obtain a range of degrees of cure from 0.66 to 0.99. These specimens were then tested in three-point bending to obtain creep compliance over a wide temperature range. The master curves and shift functions for each degree of cure case were obtained by time-temperature superposition. A numerical technique and direct inversion were used to calculate the stress relaxation modulus master curves from the creep compliance master curves. Direct inversion was shown to be adequate for fully cured specimens, however it underpredicts the relaxation modulus and the transition for partially cured specimens. Correlations with experimental stress relaxation data from Kim and White (1996) showed that reasonably accurate results can be obtained by creep testing followed by numerical conversion using the Hopkins-Hamming method.

Behavior of Nonlinear Viscoelastic Material Under Simultaneous Stress Relaxation in Tension and Creep in Torsion

1969 ◽  
Vol 36 (1) ◽  
pp. 22-27 ◽  
Author(s):  
J. S. Y. Lai ◽  
W. N. Findley
Keyword(s):  
Stress Relaxation ◽  
Multiple Integral ◽  
Analytical Investigation ◽  
Integral Approach ◽  
Successive Approximations ◽  
Tension Stress ◽  
Creep Tests ◽  
Direct Inversion ◽  
Nonlinear Viscoelastic ◽  
Shearing Strain

An experimental and analytical investigation is presented for simultaneous stress relaxation in tension and creep in torsion of polyurethane in the nonlinear range of stresses. The method employed a multiple integral approach with an assumed product form of kernel function to describe creep behavior. The required constants were determined from pure creep experiments on polyurethane. The tension stress and shearing strain versus time for simultaneous stress relaxation and creep were computed from results of these pure creep tests alone, and the results were compared with experiments on the same polyurethane under simultaneous stress relaxation and creep. In the method of analysis, direct inversion of the equation for creep was used as a first approximation for relaxation. Means for obtaining successive approximations and for accounting for cross effects are described. The second approximation was found to be adequate to describe the observed behavior very satisfactorily.

Indentation Creep and Relaxation Measurements of Polymers

2004 ◽  
Vol 841 ◽  
Author(s):  
Mark R. VanLandingham ◽  
Peter L. Drzal ◽  
Christopher C. White
Keyword(s):  
Stress Relaxation ◽  
Mechanical Response ◽  
Creep Compliance ◽  
Relaxation Modulus ◽  
Polymeric Materials ◽  
Indentation Creep ◽  
Dimethyl Siloxane ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
Creep And Stress Relaxation

ABSTRACTInstrumented indentation was used to characterize the mechanical response of polymeric materials. A model based on contact between a rigid probe and a linear viscoelastic material was used to calculate values for creep compliance and stress relaxation modulus for epoxy, poly(methyl methacrylate) (PMMA), and two poly(dimethyl siloxane) (PDMS) elastomers. Results from bulk rheometry studies were used for comparison to the indentation creep and stress relaxation results. For the two glassy polymers, the use of sharp pyramidal tips produced responses that were considerably more compliant (less stiff) than rheometry values. Additional study of the deformation remaining in epoxy after creep testing revealed that a large portion of the creep displacement measured was due to post-yield flow. Indentation creep measurements of the epoxy using a rounded conical tip also produced nonlinear responses, but the creep compliance values appeared to approach linear viscoelastic values with decreasing creep force. Responses measured for the PDMS were mainly linear elastic, but the filled PDMS exhibited some time-dependence and nonlinearity in both rheometry and indentation measurements.

scholarly journals A Combined Exponential-Power-Law Method for Interconversion between Viscoelastic Functions of Polymers and Polymer-Based Materials

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3001
Author(s):  
Vitor Dacol ◽  
Elsa Caetano ◽  
João R. Correia
Keyword(s):  
Mechanical Response ◽  
Creep Compliance ◽  
Viscoelastic Behavior ◽  
Relaxation Modulus ◽  
Creep Tests ◽  
General Applicability ◽  
Wide Range ◽  
Long Time ◽  
Linear Viscoelastic ◽  
The Time Domain

Understanding and modeling the viscoelastic behavior of polymers and polymer-based materials for a wide range of quasistatic and high strain rates is of great interest for applications in which they are subjected to mechanical loads over a long time of operation, such as the self-weight or other static loads. The creep compliance and relaxation functions used in the characterization of the mechanical response of linear viscoelastic solids are traditionally determined by conducting two separate experiments—creep tests and relaxation tests. This paper first reviews the steps involved in conducting the interconversion between creep compliance and relaxation modulus in the time domain, illustrating that the relaxation modulus can be obtained from the creep compliance. This enables the determination of the relaxation modulus from the results of creep tests, which can be easily performed in pneumatic equipment or simple compression devices and are less costly than direct relaxation tests. Some existing methods of interconversion between the creep compliance and the relaxation modulus for linear viscoelastic materials are also presented. Then, a new approximate interconversion scheme is introduced using a convenient Laplace transform and an approximated Gamma function to convert the measured creep compliance to the relaxation modulus. To demonstrate the accuracy of the fittings obtained with the method proposed, as well as its ease of implementation and general applicability, different experimental data from the literature are used.

scholarly journals Comparative Analysis of Viscoelastic Properties of Open Graded Friction Course under Dynamic and Static Loads

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1250
Author(s):  
Liding Li ◽  
Chunli Wu ◽  
Yongchun Cheng ◽  
Yongming Ai ◽  
He Li ◽  
...  
Keyword(s):  
Dynamic Modulus ◽  
Viscoelastic Properties ◽  
Functional Relationship ◽  
Creep Compliance ◽  
Relaxation Modulus ◽  
Creep Tests ◽  
Static Loads ◽  
Burgers Model ◽  
Viscoelastic Parameters ◽  
Open Graded Friction Course

The viscoelastic properties of open graded friction course (OGFC) are closely related to anti-permanent deformation ability, noise reduction ability and durability. To study the viscoelastic parameters of OGFC under dynamic and static loads and to establish the functional relationship between them, uniaxial compression creep tests and dynamic modulus tests were performed to obtain the creep compliance and the dynamic modulus of OGFC. In addition, the Burgers model, modified Burgers model, second-order extensive Maxwell model, Scott-Blair model and modified Sigmoid model were employed to quantitatively analyze the dynamic and static viscoelastic properties of OGFC. Subsequently, the relaxation modulus of OGFC was deduced by the viscoelastic theory. Then, the dynamic modulus of OGFC was calculated according to the deduced relaxation modulus. Based on the calculated values and the measured values of dynamic modulus, the functional relationship of viscoelastic parameters of OGFC under dynamic and static loads was established. The results show that the increase in test temperature has adverse effects on the viscoelastic indexes of OGFC, such as creep compliance, relaxation modulus, and dynamic modulus; the dynamic modulus derived from static creep compliance has a good linear correlation with that obtained by dynamic modulus tests, but the correlation of the phase angle is poor.

scholarly journals Research of Method for Solving Relaxation Modulus Based on Three-Point Bending Creep Test

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2021 ◽  
Author(s):  
Yazhen Sun ◽  
Zhangyi Gu ◽  
Jinchang Wang ◽  
Xuezhong Yuan
Keyword(s):  
Creep Test ◽  
Relaxation Modulus ◽  
High Viscosity ◽  
Transcendental Equation ◽  
Creep Tests ◽  
Three Point Bending ◽  
Viscoelastic Parameters ◽  
Relaxation Experiments ◽  
Laboratory Investigations ◽  
Relaxation Characteristics

A method was developed for solving the relaxation modulus of high viscosity asphalt sand (HVAS) based on the three-point bending creep test, and was verified by comparison with experimental results. In this method, firstly, a transcendental equation was obtained by the convolution, and then equations were obtained by Taylor’s formula, which were solved by Mathmatica to obtain the relaxation modulus by Newton’s method. Subsequently, the laboratory investigations of the viscoelastic parameters of the Burgers model for the HVAS by three-point bending creep tests were carried out. In addition, the method was verified by comparing the relaxation moduli with the indoor relaxation experiments. Results showed that the numerical calculation and the test data were in good agreement, and the relaxation characteristics of the HVAS were reflected more accurately. The method can be used to study the relaxation characteristics of the asphalt mixtures effectively. In addition, this study provides a research basis for road crack prevention.

scholarly journals Study on creep perform of epoxy resin for launch canister

2021 ◽  
Vol 2125 (1) ◽  
pp. 012054
Author(s):  
Fu-Quan Wei ◽  
Wen-chao Yang ◽  
Zhe-xian Zhan ◽  
Cun-gui Yu
Keyword(s):  
Epoxy Resin ◽  
Matrix Material ◽  
Element Model ◽  
Tensile Creep ◽  
Creep Model ◽  
Resin Matrix ◽  
Model Parameters ◽  
Test Results ◽  
Creep Tests ◽  
Term Creep

Abstract In order to study the creep perform of the launch canister, creep perform of the epoxy resin (matrix material) were studied. The creep model of epoxy resin was established based on Bailey-Norton model. Constant stress tensile creep tests at room temperature were carried out on epoxy resin specimens under different stress levels, and the model parameters were obtained by fitting the test data. The finite element model of the specimen was established in the ABAQUS software and the tensile simulation was carried out. The simulation results are consistent with the test results. Results show that time-hardening model can describe the short-term creep perform of epoxy resin with error less than 20%.

The Mechanical Properties of Organic Modified Epoxy Resin

2020 ◽  
Vol 43 (3) ◽  
pp. 10-14
Author(s):  
Georgel MIHU ◽  
Claudia Veronica UNGUREANU ◽  
Vasile BRIA ◽  
Marina BUNEA ◽  
Rodica CHIHAI PEȚU ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Epoxy Resin ◽  
Epoxy Matrix ◽  
Epoxy Resins ◽  
Mechanical Tests ◽  
Organic Modification ◽  
Three Point Bending ◽  
Modified Epoxy

Epoxy resins have been presenting a lot of scientific and technical interests and organic modified epoxy resins have recently receiving a great deal of attention. For obtaining the composite materials with good mechanical proprieties, a large variety of organic modification agents were used. For this study gluten and gelatin had been used as modifying agents thinking that their dispersion inside the polymer could increase the polymer biocompatibility. Equal amounts of the proteins were milled together and the obtained compound was used to form 1 to 5% weight ratios organic agents modified epoxy materials. To highlight the effect of these proteins in epoxy matrix mechanical tests as three-point bending and compression were performed.

scholarly journals Effect of rice husk (treated/untreated) and rice husk ash on fracture toughness of epoxy bio-composite

2020 ◽  
Vol 29 (1) ◽  
pp. 177-185
Author(s):  
Neeraj Bisht ◽  
Prakash Chandra Gope
Keyword(s):  
Fracture Toughness ◽  
Epoxy Resin ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Matrix Material ◽  
Secondary Reinforcement ◽  
Filler Loading ◽  
Particle Reinforcement ◽  
Pure Epoxy ◽  
Fibre Treatment

AbstractPresent work studies the effect of particle reinforcement on fracture toughness of bio-composites. The filler used has been taken as rice husk. Epoxy resin has been taken as matrix material. Composites with varying filler loading of 10, 20, 30 and 40 wt.% were fabricated. The fracture toughness was seen to be increasing with increase in filler loading. However beyond 20% there was a decrease in fracture toughness with increase in filler loading. The effect of fibre treatment on toughness was also observed. Rice husk fibres pre-treated with NaOH were used. It was observed that fracture toughness further improved due to treatment. The increase in fracture toughness was significant. Fracture toughness increased from 1.072 to 2.7465 MPa√mm for 20% reinforcement and after treatment it increased to 2.876 MPa√mm. It was observed that concentration of treatment media also affects the fracture toughness. Further the effect of hybridization was observed by addition of rice husk ash as a secondary reinforcement. The fracture toughness of the resulting composites was remarkably higher than that of pure epoxy.

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