Showing papers on "Young's modulus published in 1972"

The Part-Through Surface Crack in an Elastic Plate

Abstract: Elastic plate with part-through surface crack, determining stress intensity factor for remote tensile and bending loads

A Simple Procedure for Experimental Determination of the Longitudinal Shear Modulus of Unidirectional Composites

Abstract: to define a simple procedure for the experimental measurement of the longitudinal shear modulus using the specimen proposed by Petit (Ref. 1 ). For such a laminate, subjected to a uniaxial tensile stress in the 0° direction, the shear stresses referred to the principal axes of each layer are independent of material properties and equal to 1/2 of the applied tensile stress. Thus, the shear stress on axes at ±45° is constant through the thickness and uniform throughout the plate, except for laminate edge effects. Since this stress is known as a simple function of the applied tensile stress, it is only necessary to determine the shear strain at these ±45° angles in order to define the desired shear modulus of the unidirectional layers. This strain can be determined readily by measuring the laminate strains at 0° and 90°. The desired shear strain is then simply the difference between these two strains. This yields a very simple expression for the longitudinal shear modulus, namely:

The Young's modulus and Poisson's ratio of arsenic, antimony and bismuth

Abstract: The orientational dependences of the Young's modulus and Poisson's ratio of the A7 structure elements arsenic, antimony, and bismuth are investigated, using available experimental data of the six elastic compliance constants. The behaviour of these technical elastic constants in antimony and bismuth is shown to differ not only in degree but also in kind from that of arsenic, which exhibits the characteristics expected of a layer-like crystal; arsenic is elastically a very anisotropic material, its Young's modulus varies by a factor as large as 11.3: the largest anisotropy ratio reported for a metallic element.

Stability of a beam on an elastic foundation subjected to a follower force.

Abstract: Discussion of a new aspect in the behavior of a cantilevered beam on an elastic foundation subjected to a follower force at its free end. The critical load for flutter is found to be independent of the foundation modulus which characterizes the Winkler-type elastic imbedding. The frequency of vibration of the beam increases with increasing foundation modulus, but the magnitude of the critical load is not affected. This result is valid for any 'tangency coefficient' value.

Local Stress Measurement in Thin Thermal SiO2 Films on Si Substrates

Abstract: A novel method for local stress determination in SiO2 has been developed. The method consists in etching of SiO2 in a manner to create an oxide bridge and separating SiO2 from silicon in the bridge area. In this way, released oxide allows strain calculation and determination of compressive stress in the direction of the longitudinal axis of the bridge. Stress calculations limited to an area as small as 4×10−6 in. 2 have been obtained. The limiting factors to the accuracy of stress determination are the use of a bulk quartz modulus of elasticity, and the accuracy of the measurement of bridge deflection. The thinner the SiO2 film, the higher the accuracy of strain determination. Local stress as high as 1.78×1010 dyn/cm2 is detected in 272‐A‐thick film. The compressive stress determined by this method indicates strong thickness dependence in the films below 1500 A; the thinner the thermal oxide, the higher the average composition stress to its Si/SiO2 interface value. The method is particularly useful for th...

Practical method of conducting the indirect tensile test

Abstract: A PRACTICAL METHOD OF CONDUCTING THE INDIRECT TENSILE TEST TO DETERMINE THE TENSILE PROPERTIES OF STABILIZED MATERIALS IS DESCRIBED. A PAIR OF HALF-INCH-WIDE CURVED FACE LOADING STRIPS AND LOADING EQUIPMENT CAPABLE OF APPLYING A COM- PRESSIVE LOAD AT A CONTROLLED DEFORMATION RATE, PREFERABLY 2 INCHES PER MINUTE, MUST BE USED TO DETERMINE TENSILE STRENGTH. THE LARGE MOTORIZED GYRATORY PRESS IN USE BY THE TEXAS HIGHWAY DEPARTMENT CAN PROVIDE THIS LOADING RATE AND CAN BE EASILY MODIFIED TO ACCEPT THE LOADING STRIPS. FROM THE DIMENSIONS OF THE TEST SPECIMEN AND FAILURE LOAD, THE TENSIL STRENGTH CAN BE CALCULATED. THE DETERMINATION OF POISSON'S RATIO, THE MODULUS OF ELASTICITY, AND THE TENSILE STRAINS REQUIRES THE MEASUREMENT OF VERTICAL AND HORIZONTAL DEFORMATIONS OF THE SPECIMEN AT VARIOUS APPLIED LOADS. SIMPLE MATHEMATICAL EQUATIONS HAVE BEEN DEVELOPED TO CALCULATE THESE TENSILE PROPERTIES. /FHWA/

Flexural strength in fiber-containing concrete

Abstract: A method of making a two-phase material comprising a mix of concrete and fibers of a material having a modulus of elasticity of at least about 20 million psi substantially uniformly distributed therein with an average spacing between fibers of up to about 0.3 inch. The flexural strengths are measured for a plurality of substantially different average bond areas of the fibers per unit area in planes normal to tensile stress in test specimens of the two-phase material, and the fibers are provided and distributed in such quantity in the bulk mix that the average bond area of the fibers intersecting planes normal to the stress at known regions of highest tensile stress is sufficient to provide at least a preselected flexural strength in such regions.

A study of the relationships between time, strength, deformation and fracture of plain concrete

Abstract: Synopsis A review of previous work shows that the relationship between compressive strength and rate of strain for concrete is dependent upon curing conditions, strength and age. Tests are reported in which for strain rates slower than 2·5 7times; 10−4/s the strength of concrete was independent of strain rate. The applicability to concrete of a criterion recently established for a sandstone is examined. This criterion is based upon the incremental Poisson's ratio and defines the critical stress of concrete. The use of cored and sawn concrete cylinders produced uniform fracturing of test specimens and facilitated the study of fracture patterns resulting from varying strain rates and load histories.

Strength of short‐fiber reinforced composites

Abstract: The structural utility of short, glass fiber-reinforced epoxy composities is experimentally investigated for fiber volume fractions from 0.15 to 0.5. The strength and stiffness of systems with randomly oriented fibers are compared with those of similar composites with aligned fibers. The ultimate strength of both types of material increses in a reasonably linear fashion with volume fraction up to 0.5. For all volume fractions in this range, strength of the random composites is slightly higher than the longitudinal and much higher than the transverse strength of equivalent compsites with aligned fibers. The modulus of the random system is approximately two-thirds the longitudinal and twice the transverse modulus of the unidirectional material. The structural utility of the flow molded material is greatest in uniaxial, stiffness critical situations. The greater strength and planar isotropy of the random composites make them preferable in all strength limited or multiaxial applications.

Effect of modulus ratio on stress near a discontinuous fiber

Abstract: The effect of the fiber to matrix modulus of elasticity ratio varying from 10 to 200 was investigated for a two-dimensional plane-stress composite configuration having a simulated fiber volume fraction of 045 and containing a discontinuous fiber Uniaxial loading parallel to the fibers was considered Two independent techniques were used: moire strain analysis and finite-element analysis Displacements were measured from four experimental models by utilizing optical fringe-multiplication techniques The finite-element method yielded stresses which agreed closely with those obtained from the experimental analysis Matrix stress-concentration factor near the discontinuous fiber was found to increase rapidly with increasing modulus ratio, reaching a value of 20 for a modulus ratio of 200 The finite-element method was shown to be a valuable tool for micromechanical stress analysis of composite materials, and the accuracy of strain analysis by moire-fringemultiplication techniques was demonstrated for problems containing sever strain gradients

Dynamic‐mechanical and tensile properties of poly(vinyl chloride). Influence of thermal history and crystallinity

Abstract: The dynamic-mechanical properties as a function of temperature and the low- and high-speed tensile properties at 23°C have been determined on specimens of conventional suspension-polymerized PVC and of low-temperature-polymerized PVC roll milled and then compression molded at different temperatures. It has been found that the main transition α and the shear modulus above Tα depend on the thermal history and are strongly affected by crystallinity, whereas the dynamic-mechanical spectrum below Tα is not influenced by these parameters. Room-temperature tensile modulus and yield properties are very little affected by processing history and crystallinity. The elongation at break and the fracture energy, on the contrary, increase, at any fixed strain rate, for conventional PVC with milling temperature. The same trend has been found for low-temperature PVC, but the elongation at break-versus-temperature curve is shifted, as a whole, toward higher temperatures by approximately 50°C. Such results are discussed in terms of homogeneity of the specimens, which is controlled by the melting process of the crystallites. Stereoscanning electron micrographs of fracture surfaces appear to substantiate these conclusions.

Elastic Constants of Bulk Polymers

Abstract: : In previous work, a static multi-modulus technique was used for the simultaneous determination of Young's and bulk moduli on a single specimen of several polymeric materials. Now additional data have been obtained on a series of plasticized polyvinyl chloride polymers, on a series of polyphenyl-quinoxalines, cured with varying amounts of crosslinking agent, and on several other individual polymers. All the new data fit the same pattern as the earlier data. It was found that there is an optimum plasticizer content for PVC which maximizes moduli characteristics. In the case of the polyphenylquinoxaline, the elastic properties remained constant at all crosslinking agent concentrations. (Author)

Connexions between the moduli for anistropic elastic materials

Abstract: For homogeneous isotropic elastic materials there are simple interrelations connecting Young's modulus, Poisson's ratio, the rigidity modulus and the modulus of compression. However for anisotropic materials the situation is quite different. Young's modulus is a function of direction and Poisson's ratio and the rigidity modulus are functions of pairs of orthogonal directions. Here some simple universal connexions between the moduli for various directions are simply derived for general anisotropic materials. No particular symmetry is assumed in the material.

Tensile properties of PRD-49 fiber in epoxy matrix

Abstract: Recently a high-modulus and high-strength organic fiber, identified as PRD-49-III by the manufacturer, became commercially available. To assess the fiber performance and its potential as a reinforcement for fiber composites, the tensile properties of the fiber in an epoxy matrix were determined. During this study over 6000 fiber/epoxy strands were made using the filament winding process; these strands were representative samples taken from over 60 lb of single-end fiber. The fiber uniformity, its strength distribution at room and LN2 temperature, stress-strain characteristics, and the strain rate effect on the fiber strength were evaluated.

Rheology of building materials

Abstract: This document is a survey of the longterm deformations of building materials. A description of these deformations, common to all the materials, is given. The following materials are considered: concrete, cellular concrete, wood, fiberboard, particle board, plywood, and to a lesser extent polymers and aluminium. The influences of time, stress, temperature and moisture are discussed.

Influence of the Shape of Dispersed Particles on the Elastic Behavior of Composite Materials

Abstract: : Young's modulus was measured on a series of composites of magnesium oxide containing low concentrations of graphite in the shape of flakes, fibers and nearly spherical particles. Comparison of the measured modulus with predictions of elastic behavior based on particle shape was in excellent agreement. The results indicate not only that accurate predictions of elastic moduli are possible, but also, that dispersed particle shape has a dominating influence on the elastic properties of composite materials at low concentrations of an included phase. (Author)

An instrument for measuring rheological properties by bending. Application to food materials of plant origin.

Abstract: A new instrument, the MITEX MK II Bending Tester, is described as a means of measuring the following rheological properties of solid foods: bending moment, curvature, bending rigidity, modulus of elasticity, curvature set and bending moment loss. Equations applicable to bending and results of measurements on samples of celery, carrot, apple and potato are presented. Changes of the modulus of elasticity in relation to the time of exposure of sample strips to the ambient atmosphere, and graphical and mathematical treatment of the data for estimating a total ‘adjusted time’ (age) of a particular sample are discussed.