scholarly journals Mechanical Behaviour at Low Strains of LDPE Foams with Cell Sizes in the Microcellular Range: Advantages of Using These Materials in Structural Elements

2008 ◽  
Vol 27 (6) ◽  
pp. 347-362 ◽  
Author(s):  
M.A. Rodriguez-Perez ◽  
J. Lobos ◽  
C.A. Perez-Muñoz ◽  
J.A. de Saja ◽  
L. Gonzalez ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Cell Size ◽  
Mechanical Behaviour ◽  
Cellular Structure ◽  
Mechanical Response ◽  
Young's Modulus ◽  
Production Method ◽  
Constant Density ◽  
Structural Elements ◽  
Compression Moulding

This paper presents the production method and the compressive mechanical response at low strains for a collection of polyethylene foams with high densities and cell sizes in the microcellular range. The materials were produced using an improved compression moulding technique that allows and independent control of density and cell size. The materials had a relative density between 0.27 and 0.92, an homogeneous and multi-structured cellular structure with dense skin and foamed core and cell sizes in the range 30 to 100 microns. The Young's modulus decreased with density. For relative densities higher than 0.7, the reduced Young's modulus of the foams was higher than that of the solid. In addition, it has been proved that variations in the cell size at constant density did not influence the Young's modulus. The advantages of using these materials for the production of plastic pipes have been analysed. In comparison with a solid pipe a reduction of the weight of foamed pipes loaded in compression of up to 40% can be reached.

Mechanical Behaviour of High Density Polyethylene Based Foams

2009 ◽  
Vol 620-622 ◽  
pp. 781-784
Author(s):  
Juan Lobos ◽  
Miguel A. Rodríguez-Pérez ◽  
Miguel del Carpio ◽  
Jose A. de Saja
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Cell Size ◽  
Surface Quality ◽  
Elastic Properties ◽  
Mechanical Behaviour ◽  
High Density Polyethylene ◽  
Cellular Structure ◽  
High Density ◽  
Linear Relationships

This paper presents the mechanical properties of a collection of high density Polyethylene based foams. The produced materials are characterised by a reduction in density up to 60%, an excellent surface quality, cell sizes in the microcellular range (around 50 microns) and a multi-structured cellular structure (cranial structure) with dense skin and foamed core. The mechanical properties of these materials showed linear relationships between Young’s modulus and density for densities above 0.7 g/cm3. In addition, variations in the cell size did not influence the elastic properties.

scholarly journals The effect of processing parameters on the mechanical characteristics of PLA produced by a 3D FFF printer

2020 ◽  
Vol 111 (3-4) ◽  
pp. 695-709
Author(s):  
H. Gonabadi ◽  
A. Yadav ◽  
S. J. Bull
Keyword(s):  
Tensile Strength ◽  
Young’S Modulus ◽  
Process Parameters ◽  
Mechanical Response ◽  
Complex Geometry ◽  
Young's Modulus ◽  
Laminate Plate ◽  
Surface Strain ◽  
Image Correlation ◽  
Build Orientation

Abstract 3D printing by fused filament fabrication (FFF) provides an innovative manufacturing method for complex geometry components. Since FFF is a layered manufacturing process, effects of process parameters are of concern when plastic materials such as polylactic acid (PLA), polystyrene and nylon are used. This study explores how the process parameters, e.g. build orientation and infill pattern/density, affect the mechanical response of PLA samples produced using FFF. Digital image correlation (DIC) was employed to get full-field surface-strain measurements. The results show the influence of build orientation and infill density is significant. For on-edge orientation, the tensile strength and Young’s modulus were 55 MPa and 3.5 GPa respectively, which were about 91% and 40% less for the upright orientation, demonstrating a significant anisotropy. The tensile strength and Young’s modulus increased with increasing infill density. In contrast, different infill patterns have no significant effect. Considering the influence of build orientation, based on the experimental results, a constitutive model derived from the laminate plate theory was employed. The material parameters were determined by tensile tests. Results demonstrated a reasonable agreement between the experimental data and the predictive model. Similar anisotropy to tension was observed in shear tests; shear modulus and shear strength for 45° flat orientation were about 1.55 GPa and 36 MPa, whereas for upright specimens they were about 0.95 GPa and 18 MPa, respectively. The findings provide a framework for systematic mechanical characterisation of 3D-printed polymers and potential ways of choosing process parameters to maximise performance for a given design.

Mechanical Property Determination of Bone Through Nanoindentation Testing and Finite Element Simulation

2007 ◽  
Author(s):  
Jingzhou Zhang ◽  
Timothy C. Ovaert
Keyword(s):  
Young’S Modulus ◽  
Mechanical Response ◽  
Bone Cells ◽  
Young's Modulus ◽  
Maximum Load ◽  
Indentation Creep ◽  
Testing Conditions ◽  
Element Simulation ◽  
Unloading Rate ◽  
Testing Condition

Measurement of the mechanical properties of bone is important for estimation of the local mechanical response of bone cells to loading experienced on a larger scale. An increasing number of measurements of the hardness and Young’s modulus of bone tissue have been undertaken using nanoindentation [1,2]. However, testing conditions have not been uniform. The interactions that can occur between testing condition parameters were considered in this study, and average hardness and Young’s modulus were obtained as a function of indentation creep testing conditions (maximum load, loading/unloading rate (both equal in magnitude), load-holding time, and indenter shape).

scholarly journals An Experimental–Numerical Approach for Modelling the Mechanical Behaviour of a Pneumatic Tyre for Agricultural Machines

2020 ◽  
Vol 10 (10) ◽  
pp. 3481 ◽  
Author(s):  
Alexandros Sotirios Anifantis ◽  
Maurizio Cutini ◽  
Marco Bietresato
Keyword(s):  
Young’S Modulus ◽  
Mechanical Behaviour ◽  
Young's Modulus ◽  
Elastic Field ◽  
Numerical Approach ◽  
Fe Model ◽  
Real Scale ◽  
Tread Rubber ◽  
Agricultural Machines

The mechanical behaviour of an agricultural tyre is a matter of extreme interest as it is related to the comfort of operators, to the adherence of agricultural machines, and to the compaction of agricultural soil. Moreover, the deformability of the tyres plays a fundamental role in vehicle stability in terms of side rollover. The behaviour of a loaded tyre during its deformation is complex, due to the combined contributions of the carcass components, the tread rubber and the air contained within it. Therefore, this study proposes an experimental–numerical approach for the mechanical characterization of agricultural tyres based on real-scale experiments and matches these results with a finite-element (FE) model. The tyre flattening in the elastic field has been described using two coefficients (Young’s modulus “E”, Poisson’s ratio “ν”), whose values have been identified with an iterative FEM procedure. The proposed approach was applied to two different tyres (420/85 R24 and 460/85 R34), each one inflated at two different pressures (1.0 bar and 1.6 bar). Young’s modulus was appreciated to be highly variable with the inflation pressure “p” of the tyres. Furthermore, the response surface methodology was applied to find two mathematical regression models, useful for studying the variations of the tyre footprint dimensions according to the type of tyre. This simple approach can be applied in other simulations without suffering any loss of accuracy in the description of the phenomenon.

scholarly journals Nucleotides-Induced Changes in the Mechanical Properties of Living Endothelial Cells and Astrocytes, Analyzed by Atomic Force Microscopy

2021 ◽  
Vol 22 (2) ◽  
pp. 624
Author(s):  
Juan Carlos Gil-Redondo ◽  
Jagoba Iturri ◽  
Felipe Ortega ◽  
Raquel Pérez-Sen ◽  
Andreas Weber ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Endothelial Cells ◽  
Young’S Modulus ◽  
Mechanical Response ◽  
Adhesion Force ◽  
Young's Modulus ◽  
Nucleotide Receptors ◽  
Receptor Stimulation ◽  
Force Microscopy ◽  
Atomic Force

Endothelial cells and astrocytes preferentially express metabotropic P2Y nucleotide receptors, which are involved in the maintenance of vascular and neural function. Among these, P2Y1 and P2Y2 receptors appear as main actors, since their stimulation induces intracellular calcium mobilization and activates signaling cascades linked to cytoskeletal reorganization. In the present work, we have analyzed, by means of atomic force microscopy (AFM) in force spectroscopy mode, the mechanical response of human umbilical vein endothelial cells (HUVEC) and astrocytes upon 2MeSADP and UTP stimulation. This approach allows for simultaneous measurement of variations in factors such as Young’s modulus, maximum adhesion force and rupture event formation, which reflect the potential changes in both the stiffness and adhesiveness of the plasma membrane. The largest effect was observed in both endothelial cells and astrocytes after P2Y2 receptor stimulation with UTP. Such exposure to UTP doubled the Young’s modulus and reduced both the adhesion force and the number of rupture events. In astrocytes, 2MeSADP stimulation also had a remarkable effect on AFM parameters. Additional studies performed with the selective P2Y1 and P2Y13 receptor antagonists revealed that the 2MeSADP-induced mechanical changes were mediated by the P2Y13 receptor, although they were negatively modulated by P2Y1 receptor stimulation. Hence, our results demonstrate that AFM can be a very useful tool to evaluate functional native nucleotide receptors in living cells.

scholarly journals Design of Kinematic Connectors for Microstructured Materials Produced by Additive Manufacturing

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1500
Author(s):  
Miguel R. Silva ◽  
João A. Dias-de-Oliveira ◽  
António M. Pereira ◽  
Nuno M. Alves ◽  
Álvaro M. Sampaio ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Functionally Graded Materials ◽  
Cellular Structure ◽  
Young's Modulus ◽  
Functionally Graded ◽  
Graded Materials ◽  
Mean Values ◽  
Shear Moduli ◽  
Young’S Moduli ◽  
Unit Cells

The main characteristic of materials with a functional gradient is the progressive composition or the structure variation across its geometry. This results in the properties variation in one or more specific directions, according to the functional application requirements. Cellular structure flexibility in tailoring properties is employed frequently to design functionally-graded materials. Topology optimisation methods are powerful tools to functionally graded materials design with cellular structure geometry, although continuity between adjacent unit-cells in gradient directions remains a restriction. It is mandatory to attain a manufacturable part to guarantee the connectedness between adjoining microstructures, namely by ensuring that the solid regions on the microstructure’s borders i.e., kinematic connectors) match the neighboring cells that share the same boundary. This study assesses the kinematic connectors generated by imposing local density restrictions in the initial design domain (i.e., nucleation) between topologically optimised representative unit-cells. Several kinematic connector examples are presented for two representatives unit-cells topology optimised for maximum bulk and shear moduli with different volume fractions restrictions and graduated Young’s modulus. Experimental mechanical tests (compression) were performed, and comparison studies were carried out between experimental and numerical Young’s modulus. The results for the single maximum bulk for the mean values for experimental compressive Young’s modulus (Ex¯) with 60%Vf show a deviation of 9.15%. The single maximum shear for the experimental compressive Young’s modulus mean values (Ex¯) with 60%Vf, exhibit a deviation of 11.73%. For graded structures, the experimental mean values of compressive Young’s moduli (Ex¯), compared with predicted total Young’s moduli (ESe), show a deviation of 6.96 for the bulk graded structure. The main results show that the single type representative unit-cell experimental Young’s modulus with higher volume fraction presents a minor deviation compared with homogenized data. Both (i.e., bulk and shear moduli) graded microstructures show continuity between adjacent cells. The proposed method proved to be suitable for generating kinematic connections for the design of shear and bulk graduated microstructured materials.

Compressive behavior and deformation-mode map of an open cell alumina

1990 ◽  
Vol 5 (1) ◽  
pp. 163-171 ◽  
Author(s):  
Chuong Q. Dam ◽  
Rasto Brezny ◽  
David J. Green
Keyword(s):  
Young’S Modulus ◽  
Cell Size ◽  
Young's Modulus ◽  
Porous Ceramic ◽  
Substantial Reduction ◽  
Deformation Mode ◽  
Compressive Behavior ◽  
Unstable Crack ◽  
Crushing Strength ◽  
Open Cell

Compressive behavior of an open cell, porous ceramic has been examined and compared to a prior theoretical model. The study involved (i) microstructural characterization, (ii) crushing strength and Young's modulus measurements, and (iii) construction of a deformation-mode map. Initially, the crushing behavior was found to be different than predicted theoretically. Weaker struts throughout the material fractured during the loading and this damage was accumulated until a macroscopic crack or cracks propagated through the material at the crushing stress. Further work showed the discrepancy was related to the uniformity of loading in these porous materials. The use of compliant faces on the loading rams improved the loading uniformity, leading to a substantial reduction in the experimental scatter and increasing the likelihood of unstable crack propagation events rather than damage accumulation. Both crushing strength and Young's modulus were found to be dependent on cell size, but this was considered to be a result of strut cracking at the smallest cell size. A deformation-mode map was constructed using the average stress/strain values at critical points such as the onset of crushing, the minimum crushing stress, and the densification stress. Although some of the details of the deformation map were different from that expected theoretically, the map did appear to be a useful guide to the compressive behavior.

scholarly journals Composites Based on Polypropylene and Talc: Processing Procedure and Prediction Behavior by Using Mathematical Models

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Laiza Marinho Racca ◽  
Elen Beatriz Acordi Vasques Pacheco ◽  
Luiz Carlos Bertolino ◽  
Cristiane Xavier da Silva Campos ◽  
Monica Calixto de Andrade ◽  
...  
Keyword(s):  
Particle Size ◽  
Mathematical Models ◽  
Young’S Modulus ◽  
Mechanical Behaviour ◽  
Young's Modulus ◽  
Tensile Tests ◽  
Reinforcing Effect ◽  
Thermoplastic Matrix ◽  
Processing Procedure ◽  
Sem Analyses

iPP/Talc composites were produced, with different methods of filler addition in iPP matrix. Two different grades of Talc were used for comparison. The tensile tests results showed that talc particles promoted an improvement in composite rigidity, indicating the reinforcing effect of the talc particles in the iPP matrix. However, PP/talc-based composites that were prepared from a masterbatch and with talc grade with smaller particle size showed a better efficiency on dispersion/distribution of particle filler on the thermoplastic matrix, resulting in an improvement in Young’s modulus property, even with higher filler contents. SEM analyses evaluated the composite morphologies and different mathematical models were used as a tool on prediction of mechanical behaviour of the materials. It was observed that the results of Young’s modulus of the composites can be adjusted by different models, depending on the talc characteristics and the mixing procedure used.

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