Predictions of Young’s modulus of short inorganic fiber reinforced polymer composites

An expression of Young’s modulus of short inorganic fiber reinforced polymer composites was derived based on the tensile strength equation proposed in the previous paper, and the factor affecting the Young’s modulus was analyzed. This equation was applied to estimate the Young’s modulus of short inorganic fiber reinforced polymer composites. The results showed that the relative Young’s modulus increased nonlinearly with increasing fiber volume fraction, while increased linearly with an increase of fiber length-diameter ratio. Finally, the equation was verified preliminarily by using the measured Young’s modulus of the short glass fiber (SGF) reinforced polycarbonate/acrylnitrile–butadiene–styrene copolymer composites and the polypropylene reinforced respectively with SGF and short carbon fiber reported from literature, good agreement was found between the predictions and the experimental data.     

Analysis of effect of fiber orientation on Young’s modulus for unidirectional fiber reinforced composites

Young’s modulus of unidirectional glass fiber reinforced polymer (GFRP) composites for wind energy applications were studied using analytical, numerical and experimental methods. In order to explore the effect of fiber orientation angle on the Young’s modulus of composites, from the basic theory of elastic mechanics, a procedure which can be applied to evaluate the elastic stiffness matrix of GFRP composite as an analytical function of fiber orientation angle (from 0° to 90°), was developed. At the same time, different finite element models with inclined glass fiber were developed via the ABAQUS Scripting Interface. Results indicate that Young’s modulus of the composites strongly depends on the fiber orientation angles. A U-shaped dependency of the Young’s modulus of composites on the inclined angle of fiber is found, which agree well with the experimental results. The shear modulus is found to have significant effect on the composites’ Young’s modulus, too. The effect of volume content of glass fiber on the Young’s modulus of composites was investigated. Results indicate the relation between them is nearly linear. The results of the investigation are expected to provide some design guideline for the microstructural optimization of the glass fiber reinforced composites.     

Measurement and prediction of Young’s modulus of a Pb-free solder

Accurate and reproducible measurements of the Youngs modulus of solders are complicated by the early onset of yielding, microporosity, and variations in cooling rate. In this study, we report measurements of Youngs modulus of an Sn–3.5 wt % Ag solder by two techniques: (a) loading–unloading measurements in tension, and (b) non-destructive resonant ultrasound spectroscopy. Both techniques yielded similar values of Youngs modulus. The modulus decreased with increasing microporosity, in accordance with predicted values. Cooling rate affected the Ag₃Sn intermetallic morphology, but not Youngs modulus since the distribution of the particles was relatively random. This result was confirmed by microstructure-based finite element modeling.     

On Young’s modulus of multi-walled carbon nanotubes

Carbon nanotubes (CNTs) were discovered by Iijima in 1991 as the fourth form of carbon. Carbon nanotubes are the ultimate carbon fibres because of their high Young’s modulus of ≈ 1 TPa which is very useful for load transfer in nanocomposites. In the present work, CNT/Al nanocomposites were fabricated by the powder metallurgy technique and after extrusion of the nanocomposites bright field transmission electron microscopic (TEM) studies were carried out. From the TEM images so obtained, a novel method of ascertaining the Young’s modulus of multi-walled carbon nanotubes is worked out in the present paper which turns out to be 0·9 TPa which is consistent with the experimental results.     

Investigation the effect of sintering temperature on Young’s modulus evaluation and thermal shock behavior of a cordierite–mullite based composite

A marked mismatch between CTE of cordierite and mullite in composition develops internal stress, which causes significant growth of cracks and subsequent damages which confer them a very good ability to thermal shock resistance. To investigate the effect of sintering temperature on the thermal shock resistance, the samples sintered at four different temperatures and evaluation of Young’s modulus monitored during 25 shock cycles. The results showed that densification behavior, thermomechanical properties and thermal shock resistance of this refractory was closely related to sintering temperature. Furthermore, during specific (5th to 10th) thermal-shock cycles a notable increase occurs in the Young’s modulus of the samples, this attributed to the formation of viscose bridges, which shield the tip of growing cracks.     

Prediction of Young’s modulus and Poisson ratio for foamed metals using octahedron model

Abstract

The present paper deals with the mathematical–physical expression of Young’s modulus and Poisson ratio of foamed metals. As it is known that, Young’s modulus and Poisson ratio are two basic mechanical parameters of engineering materials. Foamed metal is a class of excellent engineering materials with dual attributes of structural and functional characteristics; therefore, these two parameters are investigated for these materials, and the relevant mathematical–physical expressions are derived from the ‘octahedron model’ of porous materials in the present paper. The results show that the apparent Young’s modulus displays a quite complicated mathematical relationship to porosity of the porous body, and the apparent Poisson ratio is just a characteristic of the material constant almost not relative to porosity of the foamed metal.     

Young’s modulus and Poisson’s ratio of concrete at high temperatures: Experimental investigations

When exposed to fire, Young’s modulus of concrete degrades. Thus, exact knowledge of temperature-dependent reduction is important to determine the fire-resistance of concrete or composite members. Nevertheless, existing material properties for the Young’s and shear modulus of concrete are linked with some incertitudes.In addition, normative regulations lack information on the temperature-dependent Poisson’s ratio. In an attempt to overcome some of the existing uncertainties, experimental work was conducted to investigate elastic material properties of fire-exposed concrete. For this purpose, the Impulse Excitation Technique was used as an innovative testing technique. Based on experimental results, the authors propose new elastic material formulations for fire-exposed concrete.     

Measuring Young’s modulus of biological objects in a liquid medium using an atomic force microscope with a special probe

A special probe with a 5-μm-diameter ball fixed at the end is developed for an atomic force microscope (AFM), with the use of which it is possible to obtain more correct values of the Young’s moduli of biological objects in liquid media and eliminate the risk of damaging the sample surface. In particular, the AFM measurements with this probe in situ revealed an increase in the Young’s modulus of rat blood vessel under the action of chlorhexidine.     

Organization-oriented technology opportunities analysis based on predicting patent networks: a case of Alzheimer’s disease

Scientometrics - This study aims to investigate how to test and assess the dichotomy of roles from an organization-oriented perspective for technology opportunity analysis, in context of the...     

Free damped vibrations of a viscoelastic oscillator based on Rabotnov’s model

Free damped vibrations of a linear viscoelastic oscillator based on Rabotnov’s model involving one fractional parameter and several relaxation (retardation) times are investigated. The analytical solution is obtained in the form of two terms, one of which governs the drift of the system’s equilibrium position and is defined by the quasi-static processes of creep occurring in the system, and the other term describes damped vibrations around the equilibrium position and is determined by the systems’s inertia and energy dissipation. The drift is governed by an improper integral taken along two sides of the cut of the complex plane. Damped vibrations are determined by two complex conjugate roots of the characteristic equation, which are located in the left half-plane of the complex plane. The behaviour of the characteristic equation roots as function of the system’s parameters is shown in the complex plane. Dedicated to the bright memory of Academician Yury N. Rabotnov.     

Real-time optimization of plug-in hybrid electric vehicles based on Pontryagin’s minimum principle

Clean Technologies and Environmental Policy - Battery aging can greatly reduce the energy efficiency of plug-in hybrid electric vehicles (PHEVs). This paper presents a novel real-time energy...     

Effect of defects and loading on prediction of Young��s modulus of SWCNTs

In this paper, the influence of various vacancy and Stone-Wales defects on the Young??s modulus of single-walled carbon nanotubes is investigated via a structural model. Dispersion in experimental results is the motivation for this work. Our results show that the type of method used (loading and boundary condition) for the prediction of the Young??s modulus of SWCNTs is very important for the results. The effect of different types of defects on the Young??s modulus is also studied for zigzag and armchair nanotubes with various aspect ratios (length/diameter). A comparison of our results with those of experimental methods indicates that for the exact prediction of the Young??s modulus of SWCNTs we need to apply the correct conditions.     

Scaling of conductivity and Young’s modulus in replicated microcellular materials

Scaling exponents for the conductivity and stiffness of replicated microcellular materials exceed commonly predicted values of 1 and 2. We show here that this is caused by the fact that, in replicated microcellular materials, the solid architecture varies with the relative density: a simple derivation based on the physics of powder consolidation returns and explains the observed scaling behaviour. The same derivation also gives an explanation for Archie’s law, known to describe the conductivity of wet soils.     

Determination of the Young’s modulus of porous ß-type Ti–40Nb by finite element analysis

Macroporous ß-type Ti–40Nb compacts with particularly low stiffness suitable for biomedical applications were successfully processed by a space-holder sintering method with a total porosity range of 50–60%. The microstructure of these samples as well as their phase composition and their mechanical properties were carefully analyzed. The samples comprise macropores with 100–300 μm size formed by NaCl space-holder particles and micropores of 1–3 μm size within the sintered Ti–Nb alloy. The correlation between the mesoscopic Young’s modulus and the microporosity of the alloy was analyzed by combining compression tests, microcomputer tomography (μCT), and finite element analysis (FE). The derived relationship permits to predict the macroscopic Young’s modulus of macroporous compacts for a known morphology of the macroporosity.     

Young’s modulus evolution at high temperature of SiC refractory castables

The evolution of Young’s modulus versus temperature has been evaluated in SiC-based hydraulically bonded refractories used in waste-to-energy (WTE) plants. Two types of low cement castables (LCC) with 60 and 85 wt% of SiC aggregates have been considered. The study was conducted by the way of a high temperature ultrasonic pulse-echo technique which allowed in situ measurement of Young’s modulus during heat treatment starting from the as-cured state up to 1400 °C in air or in neutral atmosphere (Ar) and during thermal cycles at intermediate temperatures (1000 and 1200 °C). For comparison in order to facilitate interpretation, thermal expansion has also been followed by dilatometry performed in the same conditions. Results are discussed in correlation with phase transformations occurring in the oxide matrix (dehydration at low temperature, crystallization of phases in the CaO–Al₂O₃–SiO₂ system) above 800 °C and damage occurring when cooling. The influence of oxidation of SiC aggregates on elastic properties is also discussed.     

Effect of a heating–cooling cycle on elastic strain and Young’s modulus of high performance and ordinary concrete

In this paper, the variations of elastic strain and Young modulus of high performance concrete and ordinary concrete during a heating?Ccooling cycle is presented. For the HPC, two heating rates are applied: 1.5 and 0.1?°C/min corresponding respectively to accidental and service conditions. For ordinary concrete, the results of service conditions are given. The temperatures of 400 and 220?°C are the heating??s final temperature phase of the accidental and service conditions respectively. The present work analyses the differences between the value of the elastic strain and the Young??s modulus at the beginning of the test (at ambient temperature), the end of the heating part and the end of the cooling part of each variation. Indeed, during the heating phase, the corresponding heating rates are applied until successive constant temperature levels are achieved: 150, 200, 300 and 400?°C for the high-performance concrete under accidental conditions and 140, 190 and 220?°C for both high-performance and ordinary concrete under service conditions. Those applied temperatures are maintained for several hours to ensure the stabilisation of internal temperature and physico-chemical thermo dependent processes. Moreover, the influence of the difference in mix concretes between the two types of concretes and the heating rate influence on those variations is also presented.     

Simplified fractal FEA model for the estimation of the Young’s modulus of Ti foams obtained by powder metallurgy

This work reports the introduction of a new finite elements model, for the estimation of the Young’s modulus (E) of metallic foams obtained by means of powder metallurgy using a Space Holder Phase (SHP). The model is based on the reduction of the volume, and the replication of the expected porosity distribution as fractal using two different pore sizes, which depend on the SHP. Ti foams with porosities ranging from 30% to 70% were experimentally obtained and characterized to validate the model. The effect of the porosity on the Young’s modulus for the Ti foams was estimated using the proposed model, and compared to the experimental values. Estimations obtained were in excellent agreement with the experimental results, with relative errors ranging from 0.8% to 11.2%. Both, experimental and estimated values for E showed important decreases as the porosity increases: e.g. E estimations were 37.1 and 9.3 GPa for porosities of 30% and 70%, respectively. The results demonstrated the fractal behavior of the porosity for the experimental metallic foams, as well as the efficacy of the proposed model for predicting the mechanical properties of these materials, being an important tool for their design and manufacture.     

Correlation between Young’s modulus and impregnation quality of epoxy-impregnated SWCNT buckypaper

Carbon nanotube (CNT) sheets, also known as buckypaper, have high potential for structural applications due to their high volume fraction of CNT, the strongest and stiffest materials known. In this work, two different techniques, one based on positive pressure and another based on vacuum infiltration, are utilized to impregnate single-walled carbon nanotube (SWCNT) buckypaper sheets of 50–70 μm in thickness, resulting in a Young’s modulus of up to 15.4 GPa. Scanning electron microscopy demonstrates that the vacuum-based technique results in more effective impregnation of the buckypaper than the positive pressure technique. Thermogravimetry analysis of vacuum-impregnated specimens indicated a void content ranging from 5% to 32%. An advanced Mori–Tanaka-based micromechanics technique is also utilized to predict the effect of SWCNT volume fraction and void content on Young’s modulus of nanocomposites. These calculations suggest a higher void content of around 40% for the vacuum-impregnated composites.