scholarly journals Development of an Advanced Dynamic Microindentation System to Determine Local Viscoelastic Properties of Polymers

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 833 ◽  
Author(s):  
Esther Ramakers-van Dorp ◽  
Thomas Haenel ◽  
Dominik Ciongwa ◽  
Bernhard Möginger ◽  
Berenika Hausnerova
Keyword(s):  
High Density Polyethylene ◽  
Viscoelastic Properties ◽  
Thermoplastic Polyurethane ◽  
Mechanical Analysis ◽  
Polybutylene Terephthalate ◽  
Tungsten Electrode ◽  
Complex Moduli ◽  
Spatially Resolved ◽  
Material Information ◽  
Adequate Method

This study presents a microindentation system which allows spatially resolved local as well as bulk viscoelastic material information to be obtained within one instrument. The microindentation method was merged with dynamic mechanical analysis (DMA) for a tungsten cone indenter. Three tungsten cone indenters were investigated: tungsten electrode, tungsten electrode + 2% lanthanum, and tungsten electrode + rare earth elements. Only the tungsten electrode + 2% lanthanum indenter showed the sinusoidal response, and its geometry remained unaffected by the repeated indentations. Complex moduli obtained from dynamic microindentation for high-density polyethylene, polybutylene terephthalate, polycarbonate, and thermoplastic polyurethane are in agreement with the literature. Additionally, by implementing a specially developed x-y-stage, this study showed that dynamic microindentation with a tungsten cone indenter was an adequate method to determine spatially resolved local viscoelastic surface properties.

scholarly journals Preparation and Characterization of Talc Filled Thermoplastic Polyurethane/Polypropylene Blends

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Emi Govorčin Bajsić ◽  
Vesna Rek ◽  
Ivana Ćosić
Keyword(s):  
Thermal Properties ◽  
Thermoplastic Polyurethane ◽  
Mechanical Analysis ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Polypropylene Blends ◽  
Pp Blends ◽  
The Degree Of Crystallinity ◽  
Better Than

The effect of the addition of talc on the morphology and thermal properties of blends of thermoplastic polyurethane (TPU) and polypropylene (PP) was investigated. The blends of TPU and PP are incompatible because of large differences in polarities between the nonpolar crystalline PP and polar TPU and high interfacial tensions. The interaction between TPU and PP can be improved by using talc as reinforcing filler. The morphology was observed by means of scanning electron microscopy (SEM). The thermal properties of the neat polymers and unfilled and talc filled TPU/PP blends were studied by using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The addition of talc in TPU/PP blends improved miscibility in all investigated TPU/T/PP blends. The DSC results for talc filled TPU/PP blends show that the degree of crystallinity increased, which is due to the nucleating effect induced by talc particles. The reason for the increased storage modulus of blends with the incorporation of talc is due to the improved interface between polymers and filler. According to TGA results, the addition of talc enhanced thermal stability. The homogeneity of the talc filled TPU/PP blends is better than unfilled TPU/PP blends.

Viscoelastic properties of woody hemp core

Holzforschung ◽  
2011 ◽  
Vol 65 (2) ◽  
Author(s):  
Rahime Bag ◽  
Johnny Beaugrand ◽  
Patrice Dole ◽  
Bernard Kurek
Keyword(s):  
Cell Wall ◽  
Viscoelastic Properties ◽  
Specific Effect ◽  
Mechanical Analysis ◽  
Low Molecular Weight ◽  
Dielectric Analysis ◽  
Technological Transformation ◽  
Chain Mobility ◽  
Cell Wall Polymers

Abstract The aim of this study was to determine the effect of removing extractives from the woody core of hemp (chènevotte) on the chain mobility of hemicelluloses and lignins, which can react during technological transformation such as de-fibering and/or composite materials production. Extractives are molecules with low molecular weight, which are present in the cell wall matrix and can be readily removed by solvents. In the present paper, the nature and amounts of extractives, removed under different conditions and with solvents of different polarities, were determined. The mobility and structural relaxations of lignins and hemicelluloses were stu-died in situ by dynamic mechanical analysis and dielectric analysis under controlled moisture content. Extractions at low temperature led to rigidification of lignins and plasticizing of hemicelluloses, probably due to local changes by the selective removal of molecules interacting with the polymers. Probably, the accessibility of hemicelluloses to plasticizing water was increased at controlled humidity. In contrast, hot extractions including water induced rigidification of the hemi-celluloses and plasticizing of lignins. This could be related to a combination of molecule extractions and chemical modi-fications of both polymers. This interpretation is supported by the variation of activation energy for relaxation of hemi-celluloses. It can be concluded that each type of extraction has a clear specific effect on the relaxation properties of the amorphous cell wall polymers.

Impact of material concentration and distribution on composite parts manufactured via multi-material jetting

2018 ◽  
Vol 24 (5) ◽  
pp. 872-879 ◽  
Author(s):  
Nicholas Alexander Meisel ◽  
David A. Dillard ◽  
Christopher B. Williams
Keyword(s):  
Material Properties ◽  
Viscoelastic Properties ◽  
Design Space ◽  
Base Material ◽  
Material Design ◽  
Mechanical Analysis ◽  
Material Composition ◽  
Significant Shift ◽  
Content Type ◽  
Property Changes

Purpose Material jetting approximates composite material properties through deposition of base materials in a dithered pattern. This microscale, voxel-based patterning leads to macroscale property changes, which must be understood to appropriately design for this additive manufacturing (AM) process. This paper aims to identify impacts on these composites’ viscoelastic properties due to changes in base material composition and distribution caused by incomplete dithering in small features. Design/methodology/approach Dynamic mechanical analysis (DMA) is used to measure viscoelastic properties of two base PolyJet materials and seven “digital materials”. This establishes the material design space enabled by voxel-by-voxel control. Specimens of decreasing width are tested to explore effects of feature width on dithering’s ability to approximate macroscale material properties; observed changes are correlated to multi-material distribution via an analysis of ingoing layers. Findings DMA shows storage and loss moduli of preset composites trending toward the iso-strain boundary as composition changes. An added iso-stress boundary defines the property space achievable with voxel-by-voxel control. Digital materials exhibit statistically significant changes in material properties when specimen width is under 2 mm. A quantified change in same-material droplet groupings in each composite’s voxel pattern shows that dithering requires a certain geometric size to accurately approximate macroscale properties. Originality/value This paper offers the first quantification of viscoelastic properties for digital materials with respect to material composition and identification of the composite design space enabled through voxel-by-voxel control. Additionally, it identifies a significant shift in material properties with respect to feature width due to dithering pattern changes. This establishes critical design for AM guidelines for engineers designing with digital materials.

Viscoelastic Properties of PVB Interlayer for Laminated Glass Structures Used in Building Reconstructions

2019 ◽  
Vol 808 ◽  
pp. 115-122
Author(s):  
Miroslav Vokáč ◽  
Tomáš Hána ◽  
Klára V. Machalická ◽  
Martina Eliášová
Keyword(s):  
Viscoelastic Properties ◽  
Thermoplastic Polyurethane ◽  
Maxwell Model ◽  
Polyvinyl Butyral ◽  
Laminated Glass ◽  
Building Structures ◽  
Structural Element ◽  
Stress Strain ◽  
Existing Building ◽  
Material Parameters

Laminated glass is a structural element used extensively in a reconstruction of existing building structures because of its transparency and simplicity. When using laminated glass as a glass staircase, balustrades, transparent flooring, facades or other structural elements, it is advisable to consider the shear interaction of individual glass panes in the cross-section. A conservative approach where the glass panes shear interaction is not considered, is uneconomical. This interaction depends on the properties of polymeric interlayers used in lamination process. Various commercial products based on PVB (polyvinyl butyral), EVA (ethylene vinyl acetate), ionomer, or thermoplastic polyurethane (TPU) are used. Stiffness of polymers depends on temperature and duration of a load. Interlayers exhibit the viscoelastic properties and temperature dependency usually described by the generalized Maxwell model and WLF model (Williams-Landel-Ferry). Parameters of these models are the most effectively determined by Dynamic Mechanical Thermal Analysis (DMTA), where the material is cyclically loaded at different frequencies and temperatures. Material parameters were found by DMTA in shear for PVB type of interlayer Trosifol® BG R20. In addition, the experimental quasi-static loading tests in shear were performed at different loading rates and at various temperatures. These experimental stress-strain diagrams were compared to the theoretical stress-strain relations obtained from Maxwell model with material parameters based on DMTA testing. All tests were performed in Klokner Institute CTU in Prague.

Heat Built Up During Dynamic Mechanical Analysis (DMA) Testing of Rubber Specimens

2018 ◽  
Author(s):  
Roja Esmaeeli ◽  
Ashkan Nazari ◽  
Haniph Aliniagerdroudbari ◽  
Seyed Reza Hashemi ◽  
Muapper Alhadri ◽  
...  
Keyword(s):  
Dynamic Mechanical Analysis ◽  
Heat Generation ◽  
Temperature Rise ◽  
Viscoelastic Properties ◽  
Mechanical Analysis ◽  
Compression Tests ◽  
Element Analysis ◽  
Dynamic Mechanical ◽  
Fea Model ◽  
Static And Dynamic Moduli

The viscoelastic properties of rubbers play an important role in dynamic applications and are commonly measured and quantified by means of Dynamic Mechanical Analysis (DMA) tests. The rubber properties including the static and dynamic moduli are a function of temperature; and an increase in the temperature leads to a decrease in both moduli of the rubber. Due to the heat generation inside the rubber during the DMA test and the possible change of the rubber properties it is important to quantify the amount of temperature rise in the rubber specimen during the test. In this study, a Finite Element Analysis (FEA) model is used to predict the heat generation and temperature rise during the rubber DMA tests. This model is used to identify the best shape of the specimen to achieve the minimum increase in temperature during the test. The double sandwich shear test and the cyclic compression tests are considered in this study because these two tests are mostly used in industry to predict the rubber viscoelastic properties.

Optical-Mechanical Analysis of Parabolic Trough Solar Concentrators to Support Commercial Development

2013 ◽  
Author(s):  
Kenneth Biggio ◽  
Rachel Backes ◽  
Jennifer Crawford
Keyword(s):  
Design Process ◽  
Performance Metrics ◽  
Mechanical Analysis ◽  
Optical Performance ◽  
Parabolic Trough ◽  
Commercial Development ◽  
Spatially Resolved ◽  
Cost Of Energy ◽  
And Performance ◽  
The Cost

The thermal performance of parabolic trough concentrating solar collectors depends on both the structural and optical characteristics of the design. In order to reduce the cost of energy, advanced concentrating structures must significantly reduce the cost of collectors while maintaining good optical performance. This paper discusses a Finite Element Ray Tracer (FERT) that has been developed specifically to support the commercial design process. This is achieved by tying the whole of the support structure directly to its optical effects. Consequently, the optical performance metrics go beyond the typical reflector slope error RMS or average intercept factor to present the designer with spatially resolved analysis of localized performance. By incorporating this analytical method into the structural design process, collector cost and performance can be balanced efficiently and rapidly, allowing for an accelerated design period. At times, this insight has driven better, albeit unexpected, design decisions. The paper presents an overview of the development process that Abengoa R&D uses to take advantage of its analytical optical analysis capability throughout all phases of a project, as well as a review of its implementation. A selection of case studies is also presented to illustrate how FERT enables the designer to identify local areas of concern, diagnose the cause, and quickly develop possible redesign strategies. Finally, the significance of various parameters within the ray tracer are discussed.

The effect of yield damage on the viscoelastic properties of cortical bone tissue as measured by dynamic mechanical analysis

2007 ◽  
Vol 82A (3) ◽  
pp. 530-537 ◽  
Author(s):  
Yener N. Yeni ◽  
Richard R. Shaffer ◽  
Kevin C. Baker ◽  
X. Neil Dong ◽  
Michele J. Grimm ◽  
...  
Keyword(s):  
Dynamic Mechanical Analysis ◽  
Cortical Bone ◽  
Bone Tissue ◽  
Viscoelastic Properties ◽  
Mechanical Analysis ◽  
Dynamic Mechanical
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