Showing papers on "Young's modulus published in 2011"

Indentation versus tensile measurements of Young's modulus for soft biological tissues.

Abstract: In this review, we compare the reported values of Young's modulus (YM) obtained from indentation and tensile deformations of soft biological tissues. When the method of deformation is ignored, YM values for any given tissue typically span several orders of magnitude. If the method of deformation is considered, then a consistent and less ambiguous result emerges. On average, YM values for soft tissues are consistently lower when obtained by indentation deformations. We discuss the implications and potential impact of this finding.

Mechanical characterisation of basalt fibre reinforced plastic

Abstract: New perspectives have arisen on basalt fibre applications due to the potential low cost of this material together with its good mechanical performance, in particular at high temperature. The idea to fill these fibres into a polymer matrix is relatively recent and could offer very interesting perspectives that have not yet been sufficiently investigated. In this work, with the principal aim of evaluating the possibility to replace glass fibres in most of their applications, mechanical tests were carried out on comparable E-glass and basalt fibre reinforced plastic laminates. The latter were cut by square plates fabricated through vacuum bag technology. The results obtained on the two laminates were compared showing a high performance of the basalt material in terms of young modulus, compressive and bending strength, impact force and energy. These good properties suggest possible applications of basalt fibres in fields where glass composites are nowadays largely applied. The short-beam strength tests confirmed what above said by denoting an interfacial adhesion similar to that between E-glass and epoxy matrix.

The use of the PeakForceTM quantitative nanomechanical mapping AFM-based method for high-resolution Young's modulus measurement of polymers

Abstract: PeakForceTM quantitative nanomechanical mapping (QNMTM) is a new atomic force microscopy technique for measuring Young's modulus of materials with high spatial resolution and surface sensitivity by probing at the nanoscale. In this work, modulus results from PeakForce™ QNM™ using three different probes are presented for a number of different polymers with a range of Young's moduli that were measured independently by instrumented (nano) indentation testing (IIT). The results from the diamond and silicon AFM probes were consistent and in reasonable agreement with IIT values for the majority of samples. It is concluded that the technique is complementary to IIT; calibration requirements and potential improvements to the technique are discussed.

Effect of nano-CaCO3 on hydration of cement containing supplementary cementitious materials

Abstract: The efficacy of the addition of nano-CaCO3 in accelerating the hydration of ordinary Portland cement (OPC) delayed by the presence of high volumes of supplementary cementitious materials including fly ash and slag was investigated. The conduction calorimetry indicated that the early hydration of OPC was significantly accelerated by the addition of the nano-CaCO3 and the higher the amount of CaCO3 addition, the greater was the accelerating effect. The thermogravimetric analysis results showed that the amounts of added CaCO3 became slightly lower as the hydration took place; however, any new reaction products were not detected by the X-ray diffractometry analysis. The engineering properties, including microhardness and modulus of elasticity, in the early stage of the hydration were remarkably improved by the addition of nano-CaCO3. It was suggested that the seeding effect of the nano-CaCO3 particles and the nucleation of C–S–H caused the enhanced strength development.

Mechanism of reinforcement in a nanoclay/polymer composite

Abstract: Using organomodified montmorillonite (MMT) (commonly called “Nanoclay”) to reinforce polymer-based composites have raised much attention to academic and industrial sectors due to the addition of small amount of nanoclay could substantially enhance the mechanical properties of pristine polymers. However, most of the works done previously have neglected to comprehensively study the basic reinforcing mechanism of the composites, particular the interaction between nanoclay and surrounding matrix even though high tensile strength and modulus were obtained. In this paper, uniformly-dispersed nanoclay/epoxy composite samples, based on our tailor-made experiment setup were fabricated. A tensile property test was conducted to examine the mechanical properties of the samples with different nanoclay content. It was found that the Young’s modulus and tensile strength of a composite with 5 wt.% of nanoclay increased up to 34% and 25% respectively, as compared with a pristine sample. Images obtained from scanning electron microscopy (SEM) and results extracted from transmission electron microscope (TEM) proved that interlocking and bridging effects did exist in the composites. Nanoclay clusters with the diameter of 10 nm could enhance the mechanical interlocking inside the composites and thus, breaking up the crack propagation. The formation of boundaries between the nanoclay clusters and epoxy can refine the matrix grains and further improve the flexural strength of the composites.

Superstrong ultralong carbon nanotubes for mechanical energy storage.

Abstract: Energy storage in a proper form is essential for a good grid strategy. The systems developed so far mostly use batteries or capacitors in which energy is stored electrochemically or electrostatically. Mechanical energy storage is also one of the most important ways for energy conversion. In fact, water reservoirs on high mountains store mechanical energy using the gravitational potential on the earth, and the surplus energy can be mechanically stored in water pumped to a higher elevation using pumped storage methods. Other systems for mechanical energy storage were realized, such as flstoring mechanical energies by the use of a rapidly rotating mass and steel springs storing mechanical energies by their elasticity. However, such mechanical energy storage usually is operated on a macroscopic scale, and the energy density is not very high. With the fast development of nano- and micro-electromechanical systems (N/MEMS) and actuators, nanoscale mechanical energy storage is highly required. Developing a robust nonmaterial with good mechanical performance and stable supply is the fi rst step. Ultralong carbon nanotubes (CNTs) with the properties of 1‐2 TPa modulus and 100‐200 GPa strength, [ 1‐4 ] the strongest material ever known, have shown promising potential for the storage of mechanical energy, either by their deformation in the composite materials, [ 5‐7 ] or by their elastic deformation produced by stretching or compressing the pristine tubes or tube arrays. [ 8 ] Theoretical calculation suggested that the energy storage capacity, in the latter case, can be at least three orders higher than that of steel spring and several times that of the fl ywheels and lithium ion batteries. [ 9 , 10 ] The mechanical energy storage capacity of CNTs depends on their mechanical properties, while which directly depend on their molecular structures. Besides, CNTs that simultaneously have theoretically high strength (100‐200 GPa), high tensile modulus (1‐2 TPa) and high breaking strain ( > 15%) are not yet experimentally available on the macroscale. [ 2 , 11‐20 ] This is mainly due to the existence of defects in the fabricated CNTs. Even for CNTs with little defects, the highest reported breaking strain is 13.7% ± 0.3%, [ 21 ] which is still lower than the theoretical value. [ 22 , 23 ] Here we experimentally demonstrate that the as-grown defect-free CNTs with length over 10 cm, have breaking strain up to 17.5%, tensile strength up to 200 GPa and Young’s modulus up to 1.34 TPa. They could endure a continuously repeated mechanical strain-release test for over 1.8 × 10 8 times. The extraordinary mechanical performance qualifi es them with high capacity for the storage of mechanical energy. The CNTs can store mechanical energy with a density as high as 1125 Wh kg − 1 and a power density as high as 144 MW kg − 1 , indicating the CNTs can be a promising medium for the storage of mechanical energy.

Correlation between relaxations and plastic deformation, and elastic model of flow in metallic glasses and glass-forming liquids

Abstract: We study the similarity and correlations between relaxations and plastic deformation in metallic glasses (MGs) and MG-forming liquids. It is shown that the microscope plastic events, the initiation and formation of shear bands, and the mechanical yield in MGs where the atomic sites are topologically unstable induced by applied stress, can be treated as the glass to supercooled liquid state transition induced by external shear stress. On the other hand, the glass transition, the primary and secondary relaxations, plastic deformation and yield can be attributed to the free volume increase induced flow, and the flow can be modeled as the activated hopping between the inherent states in the potential energy landscape. We then propose an extended elastic model to describe the flow based on the energy landscape theory. That is, the flow activation energy density is linear proportional to the instantaneous elastic moduli, and the activation energy density ρE is determined to be a simple expression of ρ E = 10 11 G + 1 11 K . The model indicates that both shear and bulk moduli are critical parameters accounting for both the homogeneous and inhomogeneous flows in MGs and MG-forming liquids. The elastic model is experimentally certified. We show that the elastic perspectives offers a simple scenario for the flow in MGs and MG-forming liquids and are suggestive for understanding the glass transition,plastic deformation, and nature and characteristics of MGs

Advanced mechanical properties of graphene paper

Abstract: Graphene paper (GP) has been prepared by flow-directed assembly of graphene nanosheets. The mechanical properties of as-prepared GPs were investigated by tensile, indentation, and bending tests. Heat treated GPs demonstrate superior hardness, ten times that of synthetic graphite, and two times that of carbon steel; besides, their yielding strength is significantly higher than that of carbon steel. GPs show extremely high modulus of elasticity during bending test; in the range of a few terapascal. The high strength and stiffness of GP is ascribed to the interlocking-tile microstructure of individual graphene nanosheets in the paper. These outstanding mechanical properties of GPs could lead to a wide range of engineering applications.

On the elasticity of transverse isotropic soft tissues (L).

Abstract: Quantitative elastography techniques have recently been developed to estimate the shear modulus μ of soft tissues in vivo. In the case of isotropic and quasi-incompressible media, the Young's modulus E is close to 3 μ, which is not true in transverse anisotropic tissues such as muscles. In this letter, the transverse isotropic model established for hexagonal crystals is revisited in the case of soft solids. Relationships between elastic constants and Young's moduli are derived and validated on experimental data found in the literature. It is shown that 3 μ(⊥) ≤ E(⊥) ≤ 4 μ(⊥) and that E(//) cannot only be determined from the measurements of μ(//) and μ(⊥).

Effect of cross-linker density of P(NIPAM-co-AAc) microgels at solid surfaces on the swelling/shrinking behaviour and the Young’s modulus

Abstract: The effect of the amount of cross-linker in poly(N-isopropylacrylamide-co-acrylic acid) microgel particles on the swelling behaviour and their elasticity is studied. The distribution of the stiffness through the particle is also investigated. Therefore, the swelling ratio obtained from dynamic light scattering measurements in aqueous solutions is compared with the one after adsorption at polycation-coated silicon wafers. The studies of the swelling behaviour at the surface are carried out with scanning force microscopy (SFM) against liquid. The Young’s modulus is determined by indentation experiments with an SFM. With increasing amount of cross-linker, the ability to shrink as well as the shift in the lower critical solution temperature and in particle size (hysteresis) during the heating and cooling processes decreases. In addition, the particles at the surface preserve their height/width ratio at high amount of cross-linker, while at low amounts the shrinking and swelling mainly takes place with respect to changes in height. The particles show their highest Young’s modulus in the centre of the particles and become stiffer with increasing the amount of cross-linker and the temperature.

The effect of process conditions on mechanical properties of laser‐sintered nylon

Abstract: Purpose – The purpose of this paper is to measure the effect of process conditions on mechanical properties of laser‐sintered nylon 12 (Duraform®) and to determine the range of conditions that provide consistent mechanical performance for additive manufacturing.Design/methodology/approach – Tensile test specimens were fabricated over a range of well‐characterized process conditions including laser power, laser speed, scan spacing, layer thickness, build orientation, and build position. Tensile modulus, yield strength, ultimate tensile strength and elongation‐at‐fracture were measured and related to process parameters.Findings – Tensile properties are strongly related to the amount of energy deposited during scanning. Strength and modulus approach their maximum values as the energy deposited exceeds the amount needed to fully melt the applied powder. Elongation‐at‐fracture does not reach its maximum until higher energy‐melt ratio. Performance of blends with reused powder matches that of virgin powder when ...

Young modulus, mechanical and electrical properties of isolated individual and bundled single-walled boron nitride nanotubes.

Abstract: The Young modulus of individual single-walled boron nitride nanotubes (SW-BNNTs) was determined using a high-resolution transmission-electron microscope (HRTEM)-atomic force microscope (AFM) set-up. The Young modulus and maximum stress for these NTs were deduced from the analysis of the stress-strain curves, and discussed as a function of the considered value for the shell thickness of an SW-BNNT. The elastic properties of bundles of SW-BNNTs were also investigated. All these experiments revealed that SW-BNNTs are very flexible. Furthermore, the electrical behavior of these SW-BNNTs was also analyzed employing a scanning tunneling microscope (STM) holder integrated with the same HRTEM. I/V curves were measured on individual tubes as well as on bundles of SW-BNNTs.

Mechanical characterization of single bamboo fibers with nanoindentation and microtensile technique

Abstract: More mechanical information on fibers is needed for better understanding of the complex mechanical behavior of bamboo as well as optimizing design of bamboo fiber based composites. In this paper, in situ imaging nanoindentation and an improved microtensile technique were jointly used to characterize the longitudinal mechanical behavior of fibers of Moso bamboo (Phyllostachys pubescens Mazei ex H. de Lebaie) aged between 0.5 and 4 years. These methods show that 0.5-year-old fibers have similar mechanical performances to their older counterparts. The average longitudinal tensile modulus and tensile strength of Moso bamboo fibers ranges from 32 to 34.6 GPa and 1.43 to 1.69 GPa, respectively, significantly higher than nearly all the published data for wood fibers. This finding could be attributed to the microstructural characteristics of the small microfibrillar angle and scarcity of pits in bamboo fibers. Furthermore, our results directly support the assumption that the widely used Oliver-Pharr analysis method in nanoindentation test significantly underestimates the longitudinal elastic modulus of anisotropic plant cell wall.

Super deformability and Young's modulus of GaAs nanowires.

Abstract: A significant size effect on the mechanical properties of GaAs nanowires (NWs) is reported A remarkable elastic strain of approximate to 11% for NWs with diameters of 50-150 nm and obvious plastic deformation in NWs with diameters <= 25 nm are revealed The Young's modulus of the NWs can be more than double that of bulk GaAs

Properties of high-workability concrete with recycled concrete aggregate

Abstract: This study presents the effects of recycled concrete aggregate (RCA) on the key fresh and hardened properties of concrete. RCA was used to produce high-workability concrete substituting 0-100% natural coarse aggregate (NCA) by weight. The slump and slump flow of fresh concretes were determined to ensure high workability. In addition, the compressive, flexural and splitting tensile strengths, modulus of elasticity, and permeable voids of hardened concretes were determined. The test results revealed that RCA significantly decreased the workability of concrete. RCA also affected the compressive strength, modulus of elasticity, and permeable voids of concrete. At the age of 28 days, the concrete with 100% RCA provided 12.2% lower compressive strength and 17.7% lesser modulus of elasticity than the control concrete. Also, 100% RCA increased the permeable voids of 28-day old concrete by 8.2%. However, no significant negative impact of RCA was observed on the flexural and splitting tensile strengths of concrete.