scholarly journals Influence of measurement conditions and used devices on consequential creep modulus

2016 ◽  
Vol 76 ◽  
pp. 02025 ◽  
Author(s):  
Martin Reznicek ◽  
Martin Bednarik ◽  
Lenka Hylova ◽  
David Manas
Keyword(s):  
Creep Modulus

Dynamic Properties of Asphalt Binders Containing Fiber Modifiers

2010 ◽  
Vol 97-101 ◽  
pp. 724-727 ◽  
Author(s):  
Qun Shan Ye ◽  
Shao Peng Wu
Keyword(s):  
Shear Test ◽  
Dynamic Properties ◽  
Asphalt Binder ◽  
Asphalt Binders ◽  
Test Results ◽  
Modified Asphalt ◽  
Rate Versus ◽  
Complex Shear ◽  
Creep Modulus ◽  
Phase Angles

Dynamic shear test and creep shear test were employed to investigate the dynamic properties of various fiber modified asphalt binders with the fiber content of 1.0%. The test results indicate that complex shear modulus of asphalt binders containing fibers are increased while the phase angles are decreased greatly, which implies that the asphalt binder is reinforced by the addition of fibers and the elastic property of asphalt binder is improved significantly, especially at high frequency levels. The total strain during loading period and the residual strain after the creep shear test of asphalt binders are reduced greatly by the addition of fibers. Furthermore, the creep modulus of fiber modified asphalt binders is increased and the development rate versus loading time of creep modulus is decreased.

scholarly journals Modulus of Natural Rubber Crosslinked by Dicumyl Peroxide. I. Experimental Observations

1972 ◽  
Vol 45 (5) ◽  
pp. 1388-1402 ◽  
Author(s):  
L. A. Wood ◽  
G. W. Bullman ◽  
G. E. Decker
Keyword(s):  
Glass Transition ◽  
Natural Rubber ◽  
General Relation ◽  
Quantitative Measure ◽  
Cross Linking ◽  
Rigid Sphere ◽  
Dicumyl Peroxide ◽  
Shear Creep ◽  
Rubber Sheet ◽  
Creep Modulus

Abstract Natural rubber mixed with varying amounts of dicumyl peroxide are crosslinked by heating 120 min at 149° C. The quantitative measure of cross- linking was taken as the amount fp of decomposed dicumyl peroxide, the product of p, the number of parts added per hundred of rubber and f the fraction decomposed during the time of cure. The shear creep modulus G was calculated from measurements of the indentation of a flat rubber sheet by a rigid sphere. The glass transition temperature Tg, was raised about 1.2° C for each part of decomposed dicumyl peroxide. Above (Tg+12) the modulustemperature relations were linear with a slope that increased with increasing crosslinking. The creep rate was negligible except near the glass transition and at low values of fp. Values of G, read from these plots at seven temperatures, were plotted as a function of fp. The linearity of the two plots permits the derivation of the general relation: G=S(fp+B)T+H(fp+B)+A where A, B, H, and S are constants. The lines representing G as a function of fp at each temperature all intersected near the point, fp=0.45 phr, G=2.70 Mdyn cm−2(0.270 MN  m−2). . The constants were evaluated as A=2.70 Mdyn cm−2,B=−0.45 phr, S=5.925×10−3 Mdyn cm−2(phr)−1 K−1 and H=0.0684(Mdyn cm−2) (phr)−1. This equation represented satisfactorily all the data obtained at temperatures from —50 to +100° C for values of fp from about 1 to 24 phr.

Char Studies: Flame Retarded Polycarbonate/PET Blend

1994 ◽  
Vol 12 (6) ◽  
pp. 551-581 ◽  
Author(s):  
Joseph Green
Keyword(s):  
Porous Structure ◽  
Flame Retardant ◽  
Cone Calorimeter ◽  
Oxygen Index ◽  
The Other ◽  
High Oxygen Concentration ◽  
Dsc Studies ◽  
Flame Retarded ◽  
Creep Modulus ◽  
Tga And Dsc

Bromine and phosphorus were shown to be synergistic in flame retarding a polycarbonate/PET blend as measured by oxygen index. This synergy is enhanced when both elements are present in the same molecule. Cone calorimeter data confirm these observations. Chars were formed by py rolysis in the TGA apparatus, by burning at high oxygen concentration in the oxygen index apparatus and by forced combustion in the cone calorimeter. Chars formed from the polymer blend containing the brominated phosphate gave 40-50% more char by weight than when bromine, phosphorus or blends of the two were used. Analyses of the chars showed no bromine and considerable phosphorus. TGA and DSC studies suggest that the polycarbonate and the PET undergo transesterification during pyrolysis above 400°C and the brominated phosphate acts as a transesterification inhibitor or stabilizer. SEM of the chars showed a considerable difference. When the brominated phosphate was used the char had a fine porous structure and thick solid skin. The other chars showed poorer structure and less to no skin. Measurement of the properties of the chars showed the char from the polymer containing the brominated phosphate to have a creep modulus 35 times greater than the char obtained from the polymer containing the bromine flame retardant.

Effect of ageing on stiffness of very loose sand

2002 ◽  
Vol 39 (1) ◽  
pp. 149-156 ◽  
Author(s):  
J A Howie ◽  
T Shozen ◽  
Y P Vaid
Keyword(s):  
Soil Structure ◽  
Stress Ratio ◽  
Triaxial Compression ◽  
High Stress ◽  
Volumetric Strain ◽  
Compression Tests ◽  
Close Attention ◽  
Stress Ratios ◽  
Creep Modulus ◽  
Triaxial Compression Tests

The paper presents the results of laboratory triaxial compression tests to study the stiffness of very loose Fraser River sands. The stiffness has been shown to be very dependent on the time of confinement prior to shearing and the stress ratio at which the sample is aged. Higher stress ratios resulted in very low initial moduli with no ageing, but the moduli increased by several hundred percent during the first 1000 min of ageing. For ageing at a stress ratio of 1.0 (i.e., isotropic ageing), the initial moduli were higher than those for ageing at high stress ratios, but the stiffness increased by only about 60% during the first 1000 min of ageing. The rate of stiffness increase was approximately linear with the logarithm of time up to ageing times of 10 000 min (>1 week). Ageing at any stress ratio resulted in reduced contractive volumetric strain during subsequent shearing, reflecting a change in soil structure during ageing. The dεv /dεa ratio under triaxial compression loading decreased as the ageing stress ratio increased. The results suggest that close attention must be paid to the age of laboratory samples prepared to study the stress–strain response of sands at strains up to about 0.1%, particularly in studies on loose sand.Key words: sands, ageing, creep, modulus.

Creep Behavior of Lignocellulosic-Fiber/Polypropylene Matrix Composites

2012 ◽  
Vol 730-732 ◽  
pp. 295-300 ◽  
Author(s):  
José R.M. d'Almeida ◽  
Anderson L.L. da Silva
Keyword(s):  
Creep Behavior ◽  
Polymer Matrix Composites ◽  
Fiber Surface ◽  
Element Model ◽  
Matrix Composites ◽  
Chemical Treatments ◽  
Lignocellulosic Fiber ◽  
Data Points ◽  
Polypropylene Matrix ◽  
Creep Modulus

Lignocellulosic residues obtained after the sustainable harvesting of heart of palm from pejibaye (Bactris gasipaes) palms were managed to produce chopped fibers. These fibers can be used to manufacture agglomerated panels and also as reinforcement in polymer-matrix composites. Polypropylene (PP) is a convenient polymer to be loaded with these residues due to its large applications, including under-the-bonnet applications by the automotive industry. PP-pejibaye composites with 10wt% of fiber mass fraction were manufactured and their creep behavior was studied. The experimental results were suitably described analyzing the variation of the creep modulus fitting the experimental data points to the three-element model where the Kelvin-Voigt element is attached to an independent spring. The results obtained show that the incorporation of the chopped pejibaye fibers to not affect the creep performance of the composite. This behavior is very promising, since untreated fibers were used, meaning that the use of expensive and many times environmentally detrimental fiber surface chemical treatments can be avoided.

The Stiffness of Human Apophyseal Articular Cartilage as an Indicator of Joint Loading

1994 ◽  
Vol 208 (1) ◽  
pp. 33-43 ◽  
Author(s):  
M W Swanepoel ◽  
J E Smeathers ◽  
L M Adams
Keyword(s):  
Elastic Layer ◽  
Deformation Behaviour ◽  
Thickness Distribution ◽  
Joint Cartilage ◽  
Constitutive Analysis ◽  
Joint Surfaces ◽  
Low Modulus ◽  
The Mean ◽  
Creep Modulus ◽  
Semi Empirical

The stiffness and thickness distribution of healthy lumbar apophyseal cartilage was measured in 25 lumbar motion segments (L1–4). The cartilage indentation and needling techniques of Swann and Seedhom (37) were suitably altered to cope with the low modulus and small size of the joint surfaces. A load of 3.12 ± 0.19 N (mean ± s.d.) was applied to the cartilage through a hemispherical indenter of 4.756 mm diameter. The stiffness was calculated using the displacement and instantaneous load 150 ms and 2 s after the indenter first contacted the surface, and using the equations of both Waters (46) and Hayes et al. (47). The mean stiffness of apophyseal joint cartilage was 2.8 M Pa ± 4 per cent (mean ± 95 per cent confidence limit), and thickness 1.02 mm ± 3 per cent. Peripheral apophyseal joint cartilage was softer than central cartilage. The stiffnesses of the centres of the superior and inferior joint surfaces were 3.01 MPa ± 12 per cent and 3.55 MPa ± 11 per cent. Inferior surfaces had a mean thickness of 0.93 mm ± 5 per cent and stiffness of 2.88 MPa ± 7 per cent. Superior surfaces had a mean thickness of 1.10 mm ± 4 per cent and stiffness of 2.74 MPa ± 5 per cent. It was found that the stiffness of cartilage calculated according to the formula of Hayes et al. (47), based on a constitutive analysis of a thin isotropic elastic layer, was directly proportional to both the stiffness calculated using the semi-empirical formula of Waters (46), derived to describe indentation of thin rubber sheets, and the nominal compressive creep modulus calculated by dividing the mean contact stress by the strain at the deepest point of indentation. The creep modulus calculated 2 s after contact was directly proportional to the creep modulus calculated 150 ms after indenter contact, implying that deformation behaviour was uniform between these points despite variation of cartilage stiffness.

scholarly journals Polyvinyl Alcohol Hydrogel Irradiated and Acetalized for Osteochondral Defect Repair: Mechanical, Chemical, and Histological Evaluation after Implantation in Rat Knees

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
N. A. Batista ◽  
A. A. Rodrigues ◽  
V. P. Bavaresco ◽  
J. R. L. Mariolani ◽  
W. D. Belangero
Keyword(s):  
Polyvinyl Alcohol ◽  
Optical Microscopy ◽  
Foreign Body Reaction ◽  
Osteochondral Defect ◽  
Mechanical Test ◽  
Indentation Test ◽  
Histological Evaluation ◽  
Trochlear Groove ◽  
Defect Repair ◽  
Creep Modulus

Polyvinyl Alcohol (PVA) hydrogel plugs were implanted in artificial osteochondral defects on the trochlear groove of rat knees. After 0, 3, 6, 12, and 24 weeks of followup, samples containing the implants were mechanically evaluated by creep indentation test, chemically, and histologically by optical microscopy. The mechanical test pointed towards an increase of the implant creep modulus and the chemical analysis exhibited an increasing concentration of calcium and phosphorus within the implants over time. Optical microscopy showed no foreign body reaction and revealed formation, differentiation, and maintenance of new tissue at the defect/implant interface. The absence of implant wear indicated that the natural articular lubrication process was not disturbed by the implant. The performance of the irradiated and acetalized PVA was considered satisfactory for the proposed application.

Characterizing Chicken Eggshell Reinforced Polypropylene (PP)

2011 ◽  
Vol 264-265 ◽  
pp. 871-879 ◽  
Author(s):  
Sivarao ◽  
Mohd Rizal Salleh ◽  
A. Kamely ◽  
A. Tajul ◽  
Taufik
Keyword(s):  
Calcium Carbonate ◽  
Operating Temperature ◽  
Research Work ◽  
Hardness Test ◽  
Sulfated Polysaccharides ◽  
Potential Source ◽  
Chicken Eggshell ◽  
Egg Shell ◽  
Creep Modulus ◽  
Flexural Tests

Chicken eggshell (ES) is an industrial by product containing 95% calcium carbonate and its disposal constitutes a serious environmental hazard. ES contains about 95% calcium carbonate in the form of calcite and 5% organic materials such as type X collagen, sulfated polysaccharides, and other proteins. Although there have been several attempts to use eggshell components for different applications, its chemical composition and availability makes eggshell a potential source of filler for PP composites. In this research work, different proportions of chicken eggshell as bio-filler for polypropylene (PP) composite were compared with different operating temperature by creep test, hardness test and SEM photomicrographs. The eggshell had been prepared by blending and sieving them into granule size of less than 160μm. The granules were then mixed with polypropylene into four weight ratios, 10%, 20%, 30% and 40% respectively using fine extruder, where silane was used as the coupling agent. From the result, it was learnt that, the ES filler had improved Creep Strain and Creep Modulus for the operating temperatures of 34°C and 80°C. Tensile and flexural tests were also performed to study the pattern and behaviour of the chicken egg shell particulated polypropylene. In general, the findings can be concluded that not all ratios of particulation yielded positive as expected, but there were also conditions where virgin polypropylene yields better result depending on the test type and composite matrices.

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