Viscoelastic Properties of an Epoxy Resin during Cure

2001 ◽  
Vol 35 (10) ◽  
pp. 883-904 ◽  
Author(s):  
Daniel J. O'Brien ◽  
Patrick T. Mather ◽  
Scott R. White
Keyword(s):  
Epoxy Resin ◽  
Viscoelastic Properties ◽  
Entire Range ◽  
Parallel Plate ◽  
Relaxation Modulus ◽  
Material Behavior ◽  
Gel Point ◽  
Processing Conditions ◽  
Practical Model ◽  
Point Bend

The cure dependent relaxation modulus of an epoxy resin was investigated over the entire range of cure extent. Parallel plate rheometry was used to measure the material behavior below the gel point of the epoxy network. Creep testing in three-point bend was used for specimens cured past gelation. All data were converted to the stress relaxation modulus for comparison of the material behavior among the various cure states and between the two experimental techniques. The data were used to develop a practical model for predicting the cure dependence of the relaxation modulus throughout cure under varying processing conditions.

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.

Characterization of Mechanical and Viscoelastic Properties of SC-15 Epoxy Nanocomposites Reinforced With Multi-Walled Carbon Nanotubes, Nanoclay and Binary Nanoparticles

2014 ◽  
Author(s):  
Tanjheel H. Mahdi ◽  
Mohammad E. Islam ◽  
Mahesh V. Hosur ◽  
Alfred Tcherbi-Narteh ◽  
S. Jeelani
Keyword(s):  
Carbon Nanotubes ◽  
Epoxy Resin ◽  
Viscoelastic Properties ◽  
Flexural Modulus ◽  
Epoxy Nanocomposites ◽  
Multiwalled Carbon ◽  
Epoxy Resin System ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes ◽  
Binary Nanoparticles

Mechanical and viscoelastic properties of polymer nanocomposites reinforced with carboxyl functionalized multiwalled carbon nanotubes (COOH-MWCNT), montmorillonite nanoclays (MMT) and MWCNT/MMT binary nanoparticle were investigated. In this study, 0.3 wt. % of COOH-MWCNT, 2 wt. % of MMT and 0.1 wt. % COOH-MWCNT/2 wt. % MMT binary nanoparticles by weight of epoxy were incorporated to modify SC-15 epoxy resin system. The nanocomposites were subjected to flexure test, dynamic mechanical and thermomechanical analyses. Morphological study was conducted with scanning electron microscope. Addition of each of the nanoparticles in epoxy showed significant improvement in mechanical and viscoelastic properties compared to those of control ones. But, best results were obtained for addition of 0.1% MWCNT/2% MMT binary nanoparticles in epoxy. Nanocomposites modified with binary nanoparticles exhibited about 20% increase in storage modulus as well as 25° C increase in glass transition temperature. Flexural modulus for binary nanoparticle modified composites depicted about 30% improvement compared to control ones. Thus, improvement of mechanical and viscoelastic properties was achieved by incorporating binary nanoparticles to epoxy nanocomposites. The increase in properties was attributed to synergistic effect of MWCNTs and nanoclay in chemically interacting with each other and epoxy resin as well as in arresting and delaying the crack growth once initiated.

scholarly journals Changes in Color and Dynamic Viscoelastic Properties of Epoxy Resin Composites by Surface Modification of Carbon Fibers

TANSO ◽  
1996 ◽  
Vol 1996 (173) ◽  
pp. 148-153
Author(s):  
Takao Yoshikawa ◽  
Akira Kojima ◽  
Sugio Otani ◽  
Eiichi Yasuda
Keyword(s):  
Surface Modification ◽  
Epoxy Resin ◽  
Carbon Fibers ◽  
Viscoelastic Properties ◽  
Resin Composites ◽  
Epoxy Resin Composites

Cure Monitoring of Thermosets Using Disc Bimorph Transducers

2015 ◽  
Vol 220-221 ◽  
pp. 380-384
Author(s):  
Egidijus Dragašius ◽  
Inga Skiedraite
Keyword(s):  
Thin Layer ◽  
Epoxy Resin ◽  
Piezoelectric Transducers ◽  
Small Samples ◽  
Gel Point ◽  
Cure Monitoring ◽  
Flow Processes ◽  
Before And After ◽  
Resin Curing ◽  
Further Development

The article discusses the results of experiments on the further development of the method for monitoring the state of the small samples of resin and polymers during curing. The applied method is based on a change in the structure of oscillating transducers leading to variations in the form and/or mode of oscillation. The thin layer of epoxy resin was placed between two piezoelectric transducers in the form of piezoceramic plates. Curing epoxy resin forms a bimorph and its characteristics change along with variations in viscosity or, after the gel point, stiffness. It is possible to establish the level of epoxy resin curing by monitoring changes in the resonance parameters of bimorph elements. The main purpose of cure monitoring of small samples is to develop a new method for evaluating the parameters of resin both before and after the gel point thus taking into consideration that the use of rheological data measured with reference to small samples will be applied for designing or interpreting bulk-flow processes where epoxy may be considered a continuum.

Synthesis of Liquid Crystalline Epoxy Resin p-BDEPB and Cure Kinetics with 3-MeTHPA

2010 ◽  
Vol 428-429 ◽  
pp. 71-74 ◽  
Author(s):  
Jun Gang Gao ◽  
Cai Yun Zhang ◽  
Li Huo ◽  
Yuan Yuan Zhang
Keyword(s):  
Epoxy Resin ◽  
Liquid Crystalline ◽  
Allyl Bromide ◽  
Cure Kinetics ◽  
Curing Temperature ◽  
Gel Point ◽  
Liquid Crystalline Epoxy ◽  
Clearing Point ◽  
Reaction Orders ◽  
Epoxy Value

A liquid crystalline epoxy resin of p-biphenylene di-4-(2,3-epoxypropyloxy)benzoate (p-BDEPB) was synthesized from allyl bromide, 4-hydroxy ethyl benzoate and 4,4-dihydroxybiphenyl. Its structure and liquid crystalline behavior were characterized by DSC, 1H-NMR, FTIR, POM and XRD. The results are shown that this compound is smectic liquid crystalline.The melting point of p-BDEPB is 210 oC and clearing point is over 300 oC, the epoxy value is 0.312 mol/100g. The average curing Ea of p-BDEPB/3-methyl-tetrahydrophthalic anhydride (MeTHPA) system is 97.2kJ/mol. The gel point of cured-system Tgel is 89.0 oC, curing temperature Tcu is 132.5 oC and finishing temperature Tf is 146.5 oC. The curing reaction can be described by the autocatalytic Šesták-Berggren (S-B) equation, the two reaction orders m and n is 0.23 and 0.74, respectively.

Modeling Stresses in Polyimide Films

1993 ◽  
Vol 308 ◽  
Author(s):  
Michael T. Pottiger ◽  
John C. Coburn
Keyword(s):  
Finite Element Analysis ◽  
Computer Modeling ◽  
Entire Range ◽  
Applied Load ◽  
Narrow Range ◽  
A Priori ◽  
Material Behavior ◽  
Polyimide Films ◽  
Element Analysis ◽  
The Ideal

The trend towards higher density and smaller feature sizes in today's devices, and the increasing costs associated with designing and manufacturing these devices, has placed a greater emphasis on obtaining an a priori understanding of how various materials will perform in a device. A number of manufacturers have turned to computer modeling, utilizing finite element analysis to aid in the design of new devices and reduce the costs associated with preparing prototypes. The use of computer modeling requires a constitutive equation relating the response of a material to an applied load. Polymer behavior is complex and writing an equation or a series of equations that describe the behavior of the polymer over the entire range of possible temperatures and deformations is nontrivial. Instead, series of equations that describe ideal material behavior are used in an attempt to describe the behavior of real materials over a narrow range of temperatures and deformations. For solids, the ideal material response that is generally used to describe real polymer behavior is linear elasticity.

scholarly journals Contribution of glycosaminoglycans to viscoelastic tensile behavior of human ligament

2009 ◽  
Vol 106 (2) ◽  
pp. 423-431 ◽  
Author(s):  
Trevor J. Lujan ◽  
Clayton J. Underwood ◽  
Nathan T. Jacobs ◽  
Jeffrey A. Weiss
Keyword(s):  
Viscoelastic Properties ◽  
Viscoelastic Behavior ◽  
Tensile Tests ◽  
Tissue Level ◽  
Collagen Fibrils ◽  
Material Behavior ◽  
Structural Failure ◽  
Extracellular Matrix Molecules ◽  
Before And After ◽  
Different Levels

The viscoelastic properties of human ligament potentially guard against structural failure, yet the microstructural origins of these transient behaviors are unknown. Glycosaminoglycans (GAGs) are widely suspected to affect ligament viscoelasticity by forming molecular bridges between neighboring collagen fibrils. This study investigated whether GAGs directly affect viscoelastic material behavior in human medial collateral ligament (MCL) by using nondestructive tensile tests before and after degradation of GAGs with chondroitinase ABC (ChABC). Control and ChABC treatment (83% GAG removal) produced similar alterations to ligament viscoelasticity. This finding was consistent at different levels of collagen fiber stretch and tissue hydration. On average, stress relaxation increased after incubation by 2.2% (control) and 2.1% (ChABC), dynamic modulus increased after incubation by 3.6% (control) and 3.8% (ChABC), and phase shift increased after incubation by 8.5% (control) and 8.4% (ChABC). The changes in viscoelastic behavior after treatment were significantly more pronounced at lower clamp-to-clamp strain levels. A 10% difference in the water content of tested specimens had minor influence on ligament viscoelastic properties. The major finding of this study is that mechanical interactions between collagen fibrils and GAGs are unrelated to tissue-level viscoelastic mechanics in mature human MCL. These findings narrow the possible number of extracellular matrix molecules that have a direct contribution to ligament viscoelasticity.

Scaling Behaviour of the Viscoelastic Properties of a Biopolymer System Near the Gel Point

1989 ◽  
Vol 177 ◽  
Author(s):  
M. A. V. Axelos ◽  
M. Kolb
Keyword(s):  
Steady State ◽  
Percolation Theory ◽  
Viscoelastic Properties ◽  
Sol Gel ◽  
Oscillatory Shear ◽  
Gel Point ◽  
Rheological Measurements ◽  
Scaling Behaviour ◽  
Sol Gel Transition ◽  
Gel Transition

ABSTRACTRheological measurements have been performed on pectin-calcium systems close to the sol-gel transition. Two different experimental setups - steady state and oscillatory shear measurements - show scaling of the viscoelastic properties. The results of both types of measurements are consistent with each other and with scalar percolation theory.

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