Analytical Algorithms for the Blend Ratios by Fibre-bundle Tensile Curves Part Ⅱ: Calculations of the Modulus Method and the Percentage Method

The principles for the modulus method and the percentage method are established and discussed in the part following Part Ⅰ of the series papers, in which we proposed the various algorithms of the strength method and the work method. The samples of Wool/PET blended fibre bundles, the method of fibre-bundle tensile tests and the typical specific stress-extension curves from the fibre bundles with different blend ratios are the same as in Part Ⅰ. It can be found that the theoretical results estimated by the modulus and percentage methods accord with the experimental values highly though the calculations of the two methods are slightly more complex than those of the strength and work methods. Especially, using the modulus method can not only avoid the influence of the error caused by the determination of the tensile curve of no fibre breaking in stretching, Y(e), but also need not to know the tensile curves of mono-component fibre bundles in certain calculation. The latter advantage of the modulus method exists in the percentage method too, but it should adopt the improved calculation of ones.

Tensile Elastic Modulus, Strength and Fracture of δ-Al_2O_(3f)/Al Alloy Composites

Based on the experimental and theoretical analysis, the tensile elastic modulus, strength and fracture characteristics of squeeze casting δ-Al2O3/Al alloy composites were studied. The fracture characteristics of composites were observed by SEM. The elastic modulus was predicted by the finite element method based on the energy equivalence principle, and the strength was predicted by the statistical integration average method using the maximum energy criterion of composite strength. In the prediction, the distribution density functions of the fiber's. orientation and length were considered. These functions were gained by experimental measurement. It is shown that the predicted results are in agreement with the experimental values well and the microstructure feature of composites controls the fracture characteristics.

Numerical analysis of bending property of bi-modulus materials and a new method for measurement of tensile elastic modulus

In nature,there are widely distributed bi-modulus materials with different deformation characteristics under compressive and tensile stress states,such as concrete,rock and ceramics.Due to the lack of constitutive model that could reasonably consider the bi-modulus property of materials,and the lack of simple and reliable measurement methods for the tensile elastic parameters of materials,scientists and engineers always neglect the effect of the bi-modulus property of materials in engineering design and numerical simulation.To solve this problem,this study utilizes the uncoupled strain-driven constitutive model proposed by Latorre and Montáns(2020)to systematically study the distributions and magnitudes of stresses and strains of bi-modulus materials in the three-point bending test through the numerical method.Furthermore,a new method to synchronously measure the tensile and compressive elastic moduli of materials through the four-point bending test is proposed.The numerical results show that the bi-modulus property of materials has a significant effect on the stress,strain and displacement in the specimen utilized in the three-point and four-point bending tests.Meanwhile,the results from the numerical tests,in which the elastic constitutive model proposed by Latorre and Montáns(2020)is utilized,also indicate that the newly proposed measurement method has a good reliability.Although the new measurement method proposed in this study can synchronously and effectively measure the tensile and compressive elastic moduli,it cannot measure the tensile and compressive Poisson’s ratios.

Acoustic emission activity in directly tensile test on marble specimens and its tensile damage constitutive model

For understanding acoustic emission （AE） activity and accumulation of micro-damage inside rock under pure tensile state, the AE signals has been monitored on the test of directly tension on two kinds of marble specimens. A tensile constitutive model was proposed with the damage factor calculated by AE energy rate. The tensile strength of marble was discrete obviously and was sensitive to the inside microdefects and grain composition. With increasing of loading, the tensile stress-strain curve obviously showed nonlinear with the tensile tangent modulus decreasing. In repeated loading cycle, the tensile elastic modulus was less than that in the previous loading cycle because of the generation of micro damage during the prior loading. It means the linear weakening occurring in the specimens. The AE activity was corresponding with occurrence of nonlinear deformation. In the initial loading stage which only elastic deformation happened on the specimens, there were few AE events occurred; while when the nonlinear deformation happened with increasing of loading, lots of AE events were generated. The quantity and energy of AE events were proportionally related to the variation of tensile tangent modulus. The Kaiser effect of AE activity could be clearly observed in tensile cycle loading. Based on the theory of damage mechanics, the damage factor was defined by AE energy rate and the tensile damage constitutive model was proposed which only needed two property constants. The theoretical stress-strain curve was well fitted with the curve plotted with tested datum and the two property constants were easily gotten by the laboratory testing.

Effect of Testing Conditions on Fibre-Bundle Tensile Properties-Part Ⅱ: the Gauge Length and Elongation Speed in Wool Fibre Bundle Measurement

The testing conditions of a fibre bundle tensile tester (TENSOR) are elongation speed (ES), gauge length (GL), pretension, jaw pressure, environmental temperature and relative humidity, instrument linearity and sensitivity. The effects on fibre-bundle tensile properties at different GL and ES have been discussed in detail and compared with Peirce’s theories on the weaklinks and the breaking time effect. The experimental results indicate that the tensile properties of fibre bundles are strongly affected by GL and vary with different GL. The reasonable GL should be 5 15 mm rather than 3.2 mm for wool bundle measurements. The ES ranging from 20 mm/min to 40 mm/min is beneficial for obtaining comparatively stable and accurate tensile values, whereas 20 mm/min used in current testing for wool fibre bundles is at the lower limit of the suggested range. For bundle modulus measurement, the sampling interval must be selected appropriately. The new calculation of the sampling interval has been established.

Effect of Testing Conditions on Fibre-Bundle Tensile Properties Part Ⅰ: Sample Preparation, Bundle Mass and Fibre Alignment of Wool Bundles

Due to the effects of samples and testing conditions on fibre-bundle tensile behaviour, it is necessary to investigate the relationships between experimental factors and tensile properties for the fibre-bundle tensile tester (TENSOR). The effects of bundle sample preparation, fibre bundle mass and fibre alignment have been tested. The experimental results indicated that (1) the low damage in combing and no free-end fibres in the cut bundle are most important for the sample preparation; (2) the reasonable bundle mass is 400700 tex, but the tensile properties measured should be modified with the bundle mass because a small amount of bundle mass causes the scatter results, while the larger is the bundle mass, the more difficult to comb fibres parallel and to clamp fibre evenly; and (3) the fibre irregular arrangement forms a slack bundle resulting in interaction between fibres, which will affect the reproducibility and accuracy of the tensile testing.

Residual Tensile Strength of Plain Concrete Under Tensile Fatigue Loading

The functional relation between the residual tensile strength of plain concrete and number of cycles was determined. 99 tappered prism specimens of plain concrete were tested under uniaxial tensile fatigue loading. Based on the probability distribution of the residual tensile strength, the empirical expressions of the residual tensile strength corresponding to the number of cycles were obtained. The residual tensile strength attenuating curves can be used to predict the residual fatigue life of the specimen under variable-amplitude fatigue loading. There is a good correlation between residual tensile strength and residual secant elastic modulus. The relationship between the residual secant elastic modulus and number of cycles was also established.

Effect of the amount of lignin on tensile properties of single wood fibers

Chemical components are the main factors affecting the mechanical properties of wood fibers. Lignin is one of the main components of wood cell walls and has a critical effect on the mechanical properties of paper pulp and wood fiber based composites. In this study, we carried out tensile tests on single mature latewood tracheids of Chi- nese fir （Cunninghamia lanciolata （Lamb.） Hook.）, using three different delignified treatment methods to obtain different amounts of lignin. We applied single fiber tests to study the effect of the amount of lignin on mechanical tensile proper- ties of single wood fibers at the cellular level. The results show that in their dry state, the modulus of elasticity of single fi- bers decreased with the reduction in the amount of Iignin; even their absolute values were not high. The amount of lignin affects the tensile strength and elongation of single fibers considerably. Tensile strength and elongation of single fibers increase with a reduction in the amount of lignin.

Size and strain rate effects in tensile strength of penta-twinned Ag nanowires

Penta-twinned Ag nanowires（pt-AgNWs） have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform largescale atomistic simulations to investigate the influence of sample size and strain rate on the tensile strength of pt-AgNWs. The simulation results show an apparent size effect in that the nanowire strength（defined as the critical stress for dislocation nucleation） increases with decreasing wire diameter. To account for such size effect, a theoretical model involving the interaction between an emerging dislocation and the twin boundary has been developed for the surface nucleation of dislocations. It is shown that the model predictions are in quantitative agreement with the results from atomistic simulations and previous experimental studies in the literatures. The simulations also reveal that nanowire strength is strain-rate dependent, which predicts an activation volume for dislocation nucleation in the range of 1–10b^3,where b is the magnitude of the Burgers vector for a full dislocation.

Effects of porosity on tensile mechanical properties of porous FeAl intermetallics

Uniaxial tensile tests and scanning electron microscopy(SEM)experiments were carried out on the porous FeAl intermetallics(porosities of 41.1%,44.2%and 49.3%,pore size of 15−30μm)prepared by our research group to study the macroscopic mechanical properties and microscopic failure mechanism.The results show that the tensileσ−εcurves of the porous FeAl with different porosities can be divided into four stages:elasticity,yielding,strengthening and failure,without necking phenomenon.The elastic modulus,ultimate strength and elongation decrease with the increase of porosity and the elongation is much lower than 5%.A macroscopic brittle fracture appears,and the microscopic fracture mechanism is mainly intergranular fracture,depending on the Al content in the dense FeAl intermetallics.In addition,the stochastic porous model(SPM)with random pore structure size and distribution is established by designing a self-compiling generation program in FORTRAN language.Combined with the secondary development platform of finite element software ANSYS,the effective elastic moduli of the porous FeAl can be determined by elastic analysis of SPM and they are close to the experimental values,which can verify the validity of the established SPM for analyzing the elastic properties of the porous material.

Study on the Tangential Tensile Mechanical Properties of Moso Bamboo

In this work,we used tensile tests to analyze the tangential failure forms of raw bamboo and determine a relationship between tangential tensile strength,elastic modulus,position,density,and moisture content.We found that the tangential mechanical properties of the culm wall were mainly dependent on the mechanical properties of the basic structure of the thin wall.Formulas for calculating the tangential tensile strength of moso bamboo and adjusting the moisture content were also determined.The tangential tensile strength and the tangential tensile modulus of elasticity(TTMOE)followed:outer>middle>inner,and diaphragm>bamboo node>culm wall.Below the fiber saturation point,the tangential tensile strength and TTMOE values of the bamboo gradually decreased with increasing moisture content.When the moisture content was 15%,the tangential tensile strengths of the inner,middle,outer,culm wall,bamboo node,and diaphragm samples of the five-year-old moso bamboo were 3.17,3.29,3.31,3.24,3.67,and 8.85 MPa,respectively.Furthermore,their TTMOE values were 215.09,227.98,238.45,224.04,267.21,and 559.27 MPa,respectively.Hence,this study provides a theoretical basis for future research on bamboo cracking.

Mechanical Characterization of Electroplated Ni Films by Micro-tensile Testing

Mechanical properties of structural materials are particularly important for design, performance realization and reliability analysis of microelectromechanical systems （MEMS）. Furthermore, accurate database of mechanical properties at the micro scale can provide indispensable reference for establishing MEMS standard. Electroplated nickel film is one of the most favored structural materials used in MEMS, thus its mechanical properties has been studied for many years. However, the measured values show large scatter in Yotmg＇s modulus of nickel film. Young＇s modulus and yield stress of electroplated nickel film are measured by using a micro-tensile testing instrument. The tensile load applied on the specimen is measured by a load cell with accuracy 0.25 mN directly, without additional friction. Through measuring the axial stiffness coefficient of the tensile instnunent in situ, the tensile strain of the specimen is obtained by using two-serial spring model. The electroplated nickel films were fabricated from sulfarnate baths, and the gauge section is 500μm long and 10μm wide nominally, and thickness range between 25 μm and 50μm. The obtained Young＇s modulus from tensile testing is 83＋6 GPa for nickel specimens electroplated at current density of 20 mA/cm2 and it increases to 124＋5 GPa as current density is decreased to 10 mA/cm2. The phenomena are interpreted in terms of porosity of microstructure. The higher current density produced rnicrostucture with low density and high volume fraction of pores, and the microstructure of high porosity corresponds to a lower modulus. The measured values of Young＇s modulus are consistent with those of calculated from the exponential empirical formula between Young＇s modulus and porosity. The micro-tensile testing instrument can also be used for mechanical measurement of other MEMS films.

Axial Tensile Testing of Single Fibres

The mechanical and damage properties of single fibres used in fibrous composite have gained tremendous importance in recent years. These properties are used in determination of effective properties of composites by micromechanics. These are also used in the micromechanical damage modeling. Further, these properties are used as an indicator of the excellence of product by manufacturers. In the present study the axial tensile modulus, ultimate strength and failure strain of single fibres are determined for carbon and glass fibres. ASTM D3379-75 standard is followed and a number of fibers are tested for statistical analysis. The axial tensile moduli measured are 246.7 GPa and 93.3 GPa, respectively and strength are 3031.6 MPa and 2035.9 MPa, respectively for carbon and glass fibres. Further, the respective axial tensile failure strains are 0.0137 and 0.0224. The error in the measurement of axial modulus is below 8% while for axial tensile strength is below 1%.

Estimation of Single-fibre Tensile Properties from the Bundle Tensile Curve of Polyester Fibres

Fibre bundle tensile curves can be used to characterise fibre processing properties and end-use performance directly and to predict single-fibre properties in theory. In this paper, the tensile behaviour of polyester fibre-bundles has been analysed in characteristic values and diagramming. The characteristic distributions which include the symmetry distribution on right part, SRBS′ (e), on left part, SLBS′(e) and the curve on base-line modification, MBS′ (e),based on the modulus distribution, BS′ (e), as well as the frequency density function of broken fibres, B′ (e), have been derived from the tail of bundle tensile curves. The theoretical and measured results show that the most important curves are MBS′ ( e ) and B′ ( e ) and can be used to estimate the breaking-extension distribution of single fibres. Especially for MBS′(e), the modulus distribution can accurately characterize single-fibre tensile properties and is no limitation as the calculation of B′(e) because the bundle specific stress Y(e) of no fibre breaking at extension e should be found at first.

Effect of Aramid/Carbon Hybrid on the Tensile Properties of Multilayered Biaxial Weft Knitted Fabric Reinforced Composites

The effects of aramid/carbon on tensile properties of multilayered biaxial weft knitted( MBWK) fabric reinforced composites are analyzed by experiments. The tensile tests are inducted by the SHIMADZU AG-250 KNE universal material testing machine and Aramis V6 digital image correlation( DIC) technique.More specifically,the composite samples own four hybrid ratios(Na∶ Nc= 12∶ 0,8 ∶ 4,6 ∶ 6 and 4 ∶ 8). The results showed that the aramid/carbon hybrid MBWK fabric reinforced composites showed nearly linear response until reaching the maximum load and the inserting yarns distribution on the surface of MBWK fabrics reinforced composites had a great influence on the strain pattern distribution. Besides,the tensile strength,the tensile modulus and the elongation at breakage of 0° samples and 90° samples increased with the decreasing of aramid/carbon hybrid ratio. In a word,the changes of tensile strength, tensile modulus and elongation at breakage have a lot to do with the difference of aramid/carbon hybrid ratio.

RELATION BETWEEN DYNAMIC LOSS MODULUS AND DIFFUSION COEFFICIENT IN A MODIFIED PET FIBER

The mobility of polymer chain segments is shown to play a major role in the diffusion ofdisperse dyes in a copolymerization modified PET system, monoepoxy compoundCH_3 (CH_3),OCH_2CH--CH_2 modified PET. The rate of dye diffusion (diffusion coefficient D) hasbeen related to the time-dependent mechanical property, dynamic loss modulus E', which iscontrolled by the mobility of chain segments. In this modified copolyester system, the variance ofamount of modifier in the copolyester fibers causes the change in disperse dye diffusion coefficientto fiber, and in the dynamic loss modulus of the fibers, but the relationship between the diffusionand the dynamic loss modulus is in agreement with the theoretical relation derived by Bell andDumbleton. The relation obtained in this paper is:Ln D=-2. 28Ln E'+26. 81

Tensile Properties of Veins of Damselfly Wing

Microtension test of Costa and Radius veins of damselfly wing was conducted to measure tensile strength and modulus. The specimens were classified into fresh and dry depending on when the samples were prepared and tested. Fresh samples tested immediately after extracting from the fly while the dry samples were tested one year after extraction and stored in a desiccator. Measured load-displacement response and fracture load were used to calculate modulus and strength. Field Emission Scanning Electron Microscope was used to measure the fracture morphology and cross-section of the vein. The results showed that the veins are brittle and fracture surface is flat. The average strength (232 - 285 MPa) and modulus (14 - 17 GPa) of the Costa and Radius veins were nearly same for both fresh and dry samples. The tensile modulus of the veins was 8% - 10% higher than the indentation (compressive) modulus and was nearly the same as that of human bones.

Influence of Angle Ply Orientation on Tensile Properties of Carbon/Glass Hybrid Composite

Hybrid composites are considered materials of great potential for engineering applications. One advantage of hybrid composite materials for the designer is that the properties of a composite can be controlled to a considerable extent by the choice of fibers and matrix and by adjusting the orientation of the fiber. The scope for this tailoring of the properties of the material is much greater, however, when different kinds of fiber orientations are incorporated in the same resin matrix. For the study of potential of these materials, in this work specimens were prepared with different angle ply ori entation of carbon/glass hybrid with epoxy resin as an adhesive. Three orientations viz 0°/90°, 45°/45° and 30°/60° were considered for studies. Mechanical properties such as tensile strength, tensile modulus, & peak load of the hybrid com posites were determined as per ASTM standards. Vacuum bagging technique was adopted for the fabrication of hybrid specimens. It was observed that angle ply orientation at 0°/90° showed significant increase in tensile properties as compared to other orientation. Scanning electron micrographs of fractured surfaces were used for a qualitative evaluation of interfacial properties of woven carbon-glass hybrid composites. These results indicated that carbon-glass hybrid composites offered the merits of synthetic fibers.

Enhancement in Elastic Modulus of GFRP Bars by Material Hybridization

Fiber reinforced polymer (FRP) reinforcing bars for concrete structure has been extensively investigated for last two decades and a number of FRP bars are commercially available. However, one of shortcomings of the existing FRP bars is its low elastic modulus, if glass fibers are used (i.e., GFRP). The main objective of this study using the concept of material hybridization is to develop a viable hybrid FRP bar for concrete structures, especially for marine and port con- crete structures. The purposes of hybridization are to increase the elastic modulus of GFRP bar with acceptable tensile strength. Two types of hybrid GFRP bar were considered in the development: GFRP crust with steel core and GFRP bar with steel wires dispersed over the cross-section. Using E-glass fibers and unsaturated polyester resins, the hybrid GFRP bar samples of 13 mm in diameter were pultruded and tested for tensile properties. The effect of hybridization on tensile properties of GFRP bars was evaluated by comparing the results of tensile test with those of non-hybrid GFRP bars. The results of this study indicated that the elastic modulus of the hybrid GFRP bar was increased by up to 270 percent by the material hybridization. The results of the test and the future recommendations are summarized in this paper. To ensure long-term durability of the hybrid GFRP bars in waterfront structure applications, the individual and combined effects of environmental conditions on hybrid GFRP rebar itself as well as on the interface between rebar and concrete should be accessed.

Calculation of Measurement Uncertainty for Stiffness Modulus of Asphalt Mixture

Asphalt mixture is a highly heterogeneous material, which is one of the reasons for high measurements uncertainty when subjected to tests. The results of such tests are often unreliable, which may lead to making bad professional judgments. They can be avoided by carrying out reliable analyses of measurement uncertainty adequate for the research methods used and conducted before the actual research is done. This paper presents the calculation of measurements uncertainty using as an example--the determination of the stiffness modulus of the asphalt mixture, which, in turn, was accomplished using the indirect tension method. The paper also shows the employment of the basic methods of statistical analysis, such as testing two mean values and conformity tests. Essential concepts in measurements uncertainty have been compiled and the determination of the stiffness module parameters are discussed. It has been demonstrated that the biggest source of error in the stiffness modulus measuring process is the displacement measure. The aim of the research was to find the measurement uncertainty for stiffness modulus by an indirect tensile test and the presentation of examples of the used statistical methods.