Viscoelastic Response of Closed-Cell Polyurethane Foams From Half Hour-Long Creep Tests: Identification of Lomnitz Behavior

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Christian Pichler ◽  
Marcus Maier ◽  
Roman Lackner
Keyword(s):  
Creep Compliance ◽  
Polyurethane Foams ◽  
Elastic Compliance ◽  
Velocity Measurements ◽  
Creep Tests ◽  
Viscous Material ◽  
Material Parameters ◽  
Static Creep ◽  
Closed Cell ◽  
Logarithmic Type

In this paper, a protocol for interpretation of static creep tests on closed-cell polyurethane foams is defined, considering the influence of a finite loading duration when identifying creep compliance parameters. Experiments were conducted at isothermal conditions with temperatures ranging from 20 to 120 °C. The experimental results indicate Lomnitz, i.e., logarithmic-type creep behavior. We discuss uniqueness of the backcalculated parameters. Furthermore, the viscoelastic material parameters obtained were verified in independent experiments: elastic compliance by ultrasonic wave velocity measurements, viscous material parameters by relaxation tests.

Master Curve of Creep in Polymeric Off-Axis Composite Laminates

2006 ◽  
Vol 22 (3) ◽  
pp. 229-234 ◽  
Author(s):  
H-W. Hu
Keyword(s):  
Potential Theory ◽  
Fiber Orientation ◽  
Composite Laminates ◽  
Master Curve ◽  
Creep Compliance ◽  
Epoxy Composite ◽  
Elastic Compliance ◽  
Creep Tests ◽  
The One ◽  
Total Compliance

AbstractAn approach to establish a master curve for effective creep compliances of polymeric off-axis composites with various fiber orientations was presented. Carbon/epoxy composite IM7/977–3 was used to fabricate four types of off-axis specimens and then subjected to momentary creep tests after a period of initial aging. Creep compliance and elastic compliance were separated from the total compliance. Using one-parameter creep potential theory, creep compliances were transformed to effective creep compliances. After choosing a proper value for the one-parameter, all effective creep compliances with various off-axis fiber orientations were superposed into a master curve. This master curve enables us to obtain creep compliance with any off-axis fiber orientation by testing only one off-axis specimen.

scholarly journals Polyurethane Composite Foams Synthesized Using Bio-Polyols and Cellulose Filler

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3474
Author(s):  
Katarzyna Uram ◽  
Milena Leszczyńska ◽  
Aleksander Prociak ◽  
Anna Czajka ◽  
Michał Gloc ◽  
...  
Keyword(s):  
Cross Sections ◽  
Raw Materials ◽  
Polyurethane Foams ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Polyurethane Composite ◽  
Composite Foams ◽  
Closed Cell ◽  
Ft Ir ◽  
The Fourier Transform

Rigid polyurethane foams were obtained using two types of renewable raw materials: bio-polyols and a cellulose filler (ARBOCEL® P 4000 X, JRS Rettenmaier, Rosenberg, Germany). A polyurethane system containing 40 wt.% of rapeseed oil-based polyols was modified with the cellulose filler in amounts of 1, 2, and 3 php (per hundred polyols). The cellulose was incorporated into the polyol premix as filler dispersion in a petrochemical polyol made using calenders. The cellulose filler was examined in terms of the degree of crystallinity using the powder X-ray diffraction PXRD -and the presence of bonds by means of the fourier transform infrared spectroscopy FT-IR. It was found that the addition of the cellulose filler increased the number of cells in the foams in both cross-sections—parallel and perpendicular to the direction of the foam growth—while reducing the sizes of those cells. Additionally, the foams had closed cell contents of more than 90% and initial thermal conductivity coefficients of 24.8 mW/m∙K. The insulation materials were dimensionally stable, especially at temperatures close to 0 °C, which qualifies them for use as insulation at low temperatures.

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.

New strength metrics for containerboards: influences of basic papermaking factors

2018 ◽  
Vol 33 (4) ◽  
pp. 592-602
Author(s):  
Amanda Mattsson ◽  
Tetsu Uesaka
Keyword(s):  
Time Dependent ◽  
New Method ◽  
Creep Tests ◽  
Material Parameters ◽  
Dependent Failures ◽  
Short Term Strength ◽  
New Material ◽  
End Use ◽  
Future Work ◽  
Operating Window

Abstract In end-use, containerboard is subjected to a variety of loading histories, such as seconds of loading/unloading, hours of vibration, days of creep load. The fundamental question is whether the commonly measured static strength represents “strength” under these conditions. Another question is, since those time-dependent failures are notoriously variable, how to describe the probabilistic aspect. This study concerns the characterisation of these different facets of “strength”. In our earlier work, we have investigated the theoretical framework for time-dependent, probabilistic failures, and identified three material parameters: (1) characteristic strength, {S_{c}}, representing short-term strength, (2) brittleness/durability parameter, ρ, and (3) reliability parameter, β. We have also developed a new method that allows us to determine all these parameters much faster than typical creep tests. Using the new method, we have started investigating effects of basic papermaking variables on the new material parameters. Among the samples tested, the parameter ρ varied from 20 to 50, and β from 0.5 to 1.0. This suggests that, even within the current papermaking practice, there is a wide operating window to tune these new material parameters. The future work is, therefore, to find specific manufacturing variables that can systematically change these new material parameters.

Influence of service ageing on polyester-reinforced polyvinyl chloride-coated fabrics reported through mathematical material models

2018 ◽  
Vol 89 (8) ◽  
pp. 1472-1487
Author(s):  
Krzysztof Zerdzicki ◽  
Pawel Klosowski ◽  
Krzysztof Woznica
Keyword(s):  
Polyvinyl Chloride ◽  
Constitutive Models ◽  
Uniaxial Tensile ◽  
Creep Tests ◽  
Material Models ◽  
Material Parameters ◽  
Coated Fabric ◽  
Coated Fabrics ◽  
Term Creep

In this paper the coupled service (constructional tension) and environmental (sunlight, rainfalls, temperature variations) ageing influence on the polyester-reinforced polyvinyl chloride (PVC)-coated fabric VALMEX is studied. Two cases of the same fabric have been analyzed: one USED for 20 years on the real construction of the Forest Opera in Sopot (Poland), and one kept as a spare material (NOT USED). The following tests have been conducted: uniaxial tensile, biaxial tensile and long-term creep tests. The obtained results have been used for the parameter identification of the piecewise non-linear, Burgers and Bodner–Partom models. Next, the analysis of the influence of environmental conditions on the parameters of these models has been made. It has been concluded that some parameters are more and the others are less sensitive to the exposure to environmental and mechanical conditions. The change of material parameters for fill threads (due to larger deformation) is higher. The obtained results may be useful in the durability evaluation of the textile membranes reinforced with polyester threads and PVC coated. All the constitutive models with the identified parameters may be used for the numerical analysis of structures made of fabrics at the service beginning and after long-term usage.

The performance of hot mix asphalt in dynamic and static creep tests

2017 ◽  
Vol 35 (15) ◽  
pp. 1627-1634 ◽  
Author(s):  
Alireza Khavandi Khiavi ◽  
Saeed Mansoori
Keyword(s):  
Hot Mix Asphalt ◽  
Creep Tests ◽  
Static Creep

Laboratory Investigate of the Effect of Fine Aggregates on Asphalt Mixture Materials

2011 ◽  
Vol 225-226 ◽  
pp. 577-580
Author(s):  
Yong Ye ◽  
Yi Zhou Cai
Keyword(s):  
Compressive Strength ◽  
Asphalt Mixture ◽  
Aggregate Size ◽  
Asphalt Mixtures ◽  
Fine Aggregate ◽  
Test Results ◽  
Creep Tests ◽  
Aggregate Gradation ◽  
Static Creep ◽  
Fine Aggregates

The objective of this study is to investigate and evaluate the effect of fine aggregates (aggregate size smaller than or equal to 2.36 mm) on the compressive strength and creep behavior of asphalt mixtures. The variables that are considered in the study include the sizes and gradations of fine aggregate. A kind of standant aggregate gradation and four kinds of reduced aggregate gradation mixture specimens are used. Uniaxial compression and static creep tests were realized at different loading conditions. The test results showed that the different fine aggregate sizes do not result in significant differences in compressive strength and creep values using the same percentage of fine aggregates (38.4%). Only the different gradations showed a little differences for mixtures made with different gradations but same aggregate size (between 2.36 and 1.18 mm).

scholarly journals An investigation on the effects of flaky particles on the properties of asphaltic mixtures

2015 ◽  
Vol 42 (11) ◽  
pp. 865-871 ◽  
Author(s):  
Babak Kazemi Darabadi ◽  
Hasan Taherkhani
Keyword(s):  
Creep Behaviour ◽  
Permanent Deformation ◽  
Asphaltic Concrete ◽  
Test Results ◽  
Creep Tests ◽  
Air Voids ◽  
Static Creep ◽  
Different Types ◽  
Creep Stiffness ◽  
Marshall Stability

Flaky particles, because of their shape, are considered as inferior aggregates in asphaltic mixtures, and specifications usually set limits on the amount of flaky particles in asphaltic mixtures. In this study, the effects of flaky particles content on the volumetric properties, Marshall Stability and creep behaviour of hot mixed asphaltic concrete have been investigated. Specimens with two different types of gradation and specified amounts of flaky particles were made and used for Marshall Stability and static creep tests. Test results show that the Marshall Stability decreases and the air voids content of asphaltic mixture and the voids in mineral aggregate increase as the flaky particles content increases. It is also found that flaky particles cause increase in permanent deformation and decrease in creep stiffness. The creep tests also show that the recoverable deformation of the mixtures decreases as the flaky particles content increases.

Obtaining Creep Compliance Parameters Accurately from Static or Cyclic Creep Tests

2005 ◽  
Vol 2 (8) ◽  
pp. 12263 ◽  
Author(s):  
J Kim ◽  
R Roque ◽  
B Birgisson
Keyword(s):  
Creep Compliance ◽  
Cyclic Creep ◽  
Creep Tests
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