Showing papers on "Ultimate tensile strength published in 1980"

Analysis and Performance of Fiber Composites

Abstract: Preface. 1 Introduction. 1.1 Definition. 1.2 Characteristics. 1.3 Classification. 1.4 Particulate Composites. 1.5 Fiber-Reinforced Composites. 1.6 Applications of Fiber Composites. Exercise Problems. References. 2 Fibers, Matrices, and Fabrication of Composites. 2.1 Advanced Fibers. 2.1.1 Glass Fibers. 2.1.2 Carbon and Graphite Fibers. 2.1.3 Aramid Fibers. 2.1.4 Boron Fibers. 2.1.5 Other Fibers. 2.2 Matrix Materials. 2.2.1 Polymers. 2.2.2 Metals. 2.3 Fabrication of Composites. 2.3.1 Fabrication of Thermosetting Resin Matrix Composites. 2.3.2 Fabrication of Thermoplastic-Resin Matrix Composites (Short-Fiber Composites). 2.3.3 Fabrication of Metal Matrix Composites. 2.3.4 Fabrication of Ceramic Matrix Composites. Suggested Reading. 3 Behavior of Unidirectional Composites. 3.1 Introduction. 3.1.1 Nomenclature. 3.1.2 Volume and Weight Fractions. 3.2 Longitudinal Behavior of Unidirectional Composites. 3.2.1 Initial Stiffness. 3.2.2 Load Sharing. 3.2.3 Behavior beyond Initial Deformation. 3.2.4 Failure Mechanism and Strength. 3.2.5 Factors Influencing Longitudinal Strength and Stiffness. 3.3 Transverse Stiffness and Strength. 3.3.1 Constant-Stress Model. 3.3.2 Elasticity Methods of Stiffness Prediction. 3.3.3 Halpin-Tsai Equations for Transverse Modulus. 3.3.4 Transverse Strength. 3.4 Prediction of Shear Modulus. 3.5 Prediction of Poisson's Ratio. 3.6 Failure Modes. 3.6.1 Failure under Longitudinal Tensile Loads. 3.6.2 Failure under Longitudinal Compressive Loads. 3.6.3 Failure under Transverse Tensile Loads. 3.6.4 Failure under Transverse Compressive Loads. 3.6.5 Failure under In-Plane Shear Loads. 3.7 Expansion Coefficients and Transport Properties. 3.7.1 Thermal Expansion Coefficients. 3.7.2 Moisture Expansion Coefficients. 3.7.3 Transport Properties. 3.7.4 Mass Diffusion. 3.8 Typical Unidirectional Fiber Composite Properties. Exercise Problems. References. 4 Short-Fiber Composites. 4.1 Introduction. 4.2 Theories of Stress Transfer. 4.2.1 Approximate Analysis of Stress Transfer. 4.2.2 Stress Distributions from Finite-Element Analysis. 4.2.3 Average Fiber Stress. 4.3 Modulus and Strength of Short-Fiber Composites. 4.3.1 Prediction of Modulus. 4.3.2 Prediction of Strength. 4.3.3 Effect of Matrix Ductility. 4.4 Ribbon-Reinforced Composites. Exercise Problems. References. 5 Analysis of an Orthotropic Lamina. 5.1 Introduction. 5.1.1 Orthotropic Materials. 5.2 Stress-Strain Relations and Engineering Constants. 5.2.1 Stress-Strain Relations for Specially Orthotropic Lamina. 5.2.2 Stress-Strain Relations for Generally Orthotropic Lamina. 5.2.3 Transformation of Engineering Constants. 5.3 Hooke's Law and Stiffness and Compliance Matrices. 5.3.1 General Anisotropic Material. 5.3.2 Specially Orthotropic Material. 5.3.3 Transversely Isotropic Material. 5.3.4 Isotropic Material. 5.3.5 Specially Orthotropic Material under Plane Stress. 5.3.6 Compliance Tensor and Compliance Matrix. 5.3.7 Relations between Engineering Constants and Elements of Stiffness and Compliance Matrices. 5.3.8 Restrictions on Elastic Constants. 5.3.9 Transformation of Stiffness and Compliance Matrices. 5.3.10 Invariant Forms of Stiffness and Compliance Matrices. 5.4 Strengths of an Orthotropic Lamina. 5.4.1 Maximum-Stress Theory. 5.4.2 Maximum-Strain Theory. 5.4.3 Maximum-Work Theory. 5.4.4 Importance of Sign of Shear Stress on Strength of Composites. Exercise Problems. References. 6 Analysis of Laminated Composites. 6.1 Introduction. 6.2 Laminate Strains. 6.3 Variation of Stresses in a Laminate. 6.4 Resultant Forces and Moments: Synthesis of Stiffness Matrix. 6.5 Laminate Description System. 6.6 Construction and Properties of Special Laminates. 6.6.1 Symmetric Laminates. 6.6.2 Unidirectional, Cross-Ply, and Angle-Ply Laminates. 6.6.3 Quasi-isotropic Laminates. 6.7 Determination of Laminae Stresses and Strains. 6.8 Analysis of Laminates after Initial Failure. 6.9 Hygrothermal Stresses in Laminates. 6.9.1 Concepts of Thermal Stresses. 6.9.2 Hygrothermal Stress Calculations. 6.10 Laminate Analysis Through Computers. Exercise Problems. References. 7 Analysis of Laminated Plates and Beams. 7.1 Introduction. 7.2 Governing Equations for Plates. 7.2.1 Equilibrium Equations. 7.2.2 Equilibrium Equations in Terms of Displacements. 7.3 Application of Plate Theory. 7.3.1 Bending. 7.3.2 Buckling. 7.3.3 Free Vibrations. 7.4 Deformations Due to Transverse Shear. 7.4.1 First-Order Shear Deformation Theory. 7.4.2 Higher-Order Shear Deformation Theory. 7.5 Analysis of Laminated Beams. 7.5.1 Governing Equations for Laminated Beams. 7.5.2 Application of Beam Theory. Exercise Problems. References. 8 Advanced Topics in Fiber Composites. 8.1 Interlaminar Stresses and Free-Edge Effects. 8.1.1 Concepts of Interlaminar Stresses. 8.1.2 Determination of Interlaminar Stresses. 8.1.3 Effect of Stacking Sequence on Interlaminar Stresses. 8.1.4 Approximate Solutions for Interlaminar Stresses. 8.1.5 Summary. 8.2 Fracture Mechanics of Fiber Composites. 8.2.1 Introduction. 8.2.2 Fracture Mechanics Concepts and Measures of Fracture Toughness. 8.2.3 Fracture Toughness of Composite Laminates. 8.2.4 Whitney-Nuismer Failure Criteria for Notched Composites. 8.3 Joints for Composite Structures. 8.3.1 Adhesively Bonded Joints. 8.3.2 Mechanically Fastened Joints. 8.3.3 Bonded-Fastened Joints. Exercise Problems. References. 9 Performance of Fiber Composites: Fatigue, Impact, and Environmental Effects. 9.1 Fatigue. 9.1.1 Introduction. 9.1.2 Fatigue Damage. 9.1.3 Factors Influencing Fatigue Behavior of Composites. 9.1.4 Empirical Relations for Fatigue Damage and Fatigue Life. 9.1.5 Fatigue of High-Modulus Fiber-Reinforced Composites. 9.1.6 Fatigue of Short-Fiber Composites. 9.2 Impact. 9.2.1 Introduction and Fracture Process. 9.2.2 Energy-Absorbing Mechanisms and Failure Models. 9.2.3 Effect of Materials and Testing Variables on Impact Properties. 9.2.4 Hybrid Composites and Their Impact Strength. 9.2.5 Damage Due to Low-Velocity Impact. 9.3 Environmental-Interaction Effects. 9.3.1 Fiber Strength. 9.3.2 Matrix Effects. Exercise Problems. References. 10 Experimental Characterization of Composites. 10.1 Introduction. 10.2 Measurement of Physical Properties. 10.2.1 Density. 10.2.2 Constituent Weight and Volume Fractions. 10.2.3 Void Volume Fraction. 10.2.4 Thermal Expansion Coefficients. 10.2.5 Moisture Absorption and Diffusivity. 10.2.6 Moisture Expansion Coefficients. 10.3 Measurement of Mechanical Properties. 10.3.1 Properties in Tension. 10.3.2 Properties in Compression. 10.3.3 In-Place Shear Properties. 10.3.4 Flexural Properties. 10.3.5 Measures of In-Plane Fracture Toughness. 10.3.6 Interlaminar Shear Strength and Fracture Toughness. 10.3.7 Impact Properties. 10.4 Damage Identification Using Nondestructive Evaluation Techniques. 10.4.1 Ultrasonics. 10.4.2 Acoustic Emission. 10.4.3 x-Radiography. 10.4.4 Thermography. 10.4.5 Laser Shearography. 10.5 General Remarks on Characterization. Exercise Problems. References. 11 Emerging Composite Materials. 11.1 Nanocomposites. 11.2 Carbon-Carbon Composites. 11.3 Biocomposites. 11.3.1 Biofibers. 11.3.2 Wood-Plastic Composites (WPCs). 11.3.3 Biopolymers. 11.4 Composites in "Smart" Structures. Suggested Reading. Appendix 1: Matrices and Tensors. Appendix 2: Equations of Theory of Elasticity. Appendix 3: Laminate Orientation Code. Appendix 4: Properties of Fiber Composites. Appendix 5: Computer Programs for Laminate Analysis. Index.

Ultra-high-strength polyethylene filaments by solution spinning/drawing

Abstract: This paper deals with ultra-high-strength monofilaments of linear polyethylene that are produced by solution spinning and subsequent hot drawing at 120° C. The influence of the draw ratio on the mechanical and thermal properties of the fibres was investigated. Some salient features of a polyethylene filament with a draw ratio of 31.7 are: tensile strength at break=3.0 GPa, Young's modulus=90 GPa and DSC-melting point at a scan speed of 10° C min−1=145.5° C. The modulus was found to depend linearly on the draw ratio. The tensile strength tended, by contrast, to approach an upper limit at high draw ratios. Additional morphological and X-ray studies revealed an extremely good orientation of the macromolecules in the fibre direction of the highly drawn polyethylene monofilaments.

The intrinsic tensile behavior of the matrix of bovine articular cartilage and its variation with age

Abstract: To study the age dependence of the uniaxial tensile behavior of bovine articular cartilage, 216 specimens of articular cartilage from the patellofemoral joint were grouped into two age categories: those from joints with growth plates present (open physes) and those from joints without growth plates (no physes). We prepared standard, dumbbell-shaped test specimens from the three ultrastructural zones of the tissue: the superficial tangential zone, the middle zone, and the deep zone. As was done in the early works of Kempson et al. and of Woo et all., we prepared specimens whose long axes were either parallel or perpendicular to the axis of the local split line on the joint surface. In these tensile tests we observed a profound difference between the two age groups in terms of the variations in the tensile properties related to the depth below the surface. With increasing distance from the articular surface, the tensile strength and stiffness increased in the open-physis group and decreased in the no-physis group. Directional dependence of the tensile response was manifested by increased stiffness and strength of the samples oriented parallel to the split-line axis when compared with the samples oriented perpendicular to it. Distortion of the initially flat, straight-sided portion of the gauge section was observed in most of the 216 specimens immediately after the application of tensile strains. This effect casts serious doubts on all previous measurements of cross-sectional dimensional changes. At present, we believe that this distortion occurs because articular cartilage is an inhomogeneous, layered material. We also observed that cartilage exudes substantial amounts of its interstitial fluid when the applied tensile strain becomes large. These two effects create serious problems in assessing the true volumetric changes and the material properties of cartilage specimens during uniaxial tension experiments.

The Bone Mineral Content and Ultimate Compressive Strength of Lumbar Vertebrae

Abstract: The bone mineral content of 109 lumbar vertebrae from 36 different subjects was determined by dual photon absorptiometry. The mean age of the subjects was 58.5 years (range, 31 to 79 years). The ultimate strength of the vertebral bodies was determined during axial compression. Bone mineral content and ultimate compressive strength were correlated (r = 0.86) and the strength was found to increase linearly with increasing amounts of bone mineral content. No differences in this correlation were found in the four vertebral levels (L1–4) included in the study, but a difference in this correlation was found between specimens taken from male and female subjects. The results make it possible to estimate the strength of a vertebral body from the knowledge of its bone mineral content as determined by dual photon absorptiometry and provide a basis for estimations of normal and abnormal amounts of bone mineral content in the vertebrae of the lumbar spine.

Phase transformations and tensile properties of Ti-10V-2Fe-3AI

Abstract: The effect of heat treatment on the microstructure of the metastableα-Ti alloy Ti-10V-2Fe-3Al has been studied using light and electron metallography, analytical electron microscopy, and X-ray diffraction. A survey of the effects of microstructure on tensile properties of the alloy also has been conducted. It has been found that the alloy contains inclusions which are rich in Ti, S, Si, and P. The alloy has been shown to form ω-phase both athermally and isothermally. The isothermal ω can have either an ellipsoidal or a cuboidal morphology. The reasons for this are enumerated. The formation of α-phase has been studied, and three distinct modes of formation are described. A stress induced orthorhombic martensite also has been observed. The effect of this stress induced product on tensile behavior is discussed. The relative roles of inclusions and α-phase precipitates in the tensile fracture also have been examined.

Adhesion and Adsorption of Polymers

Abstract: One: Polymer Surface Interactions- Introductory Remarks- Statistical Mechanics of Surface Tension and Adsorption- Surface and Interfacial Tensions of Polymer Melts and Solutions- Donor-Acceptor Interactions at Interfaces- Surface Tension of Solids: Generalization and Reinterpretation of Critical Surface Tension- A Role of Molecular Forces in Adhesive Interactions of Polymers- Discussion- Two: Characterization of Adhesive Interfaces- Introductory Remarks- Photoacoustic Spectroscopy for the Study of Adhesion and Adsorption of Dyes and Polymers- Adhesive-Adherend Bond Joint Characterization by Auger Electron Spectroscopy and Photoelectron Spectroscopy- Techniques for Measuring Adhesive vs Cohesive Failure- Failure Characterization of a Structural Adhesive- Dielectric Relaxation Gradients in an Adhesive Bond- New Approach to the Understanding of Adhesive Interface Phenomena and Bond Strength- Discussion- Three: Polymeric Structural Adhesives- Introductory Remarks- Fracture Mechanics and Adherence of Viscoelastic Solids- The Viscoelastic Shear Behavior of a Structural Adhesive- Surface Energetics and Structural Reliability of Adhesive Bonded Metal Structures- Composition and Ageing of a Structural, Epoxy Based Film Adhesive- Viscoelastic Characterization of Structural Adhesive via Force Oscillation Experiments- Crack Healing in Semicrystalline Polymers, Block Copolymers and Filled Elastomers- Discussion- Four: Fracture Strengths in Polymeric Systems- Introductory Remarks- Criterion of Interfacial Fracture on Tensile Adhesive Joint- Deformation and Shear Strength of FRP Adhesive Joints- Stress Distribution and Strength in Shear on the Adhesive Lap Joint Loading Bending Moment- Fracture Criteria on Peeling- Superposition of Peel Rate, Temperature and Molecular Weight for T Peel Strength of Polyisobutylene- Discussion- Author Index

Experimental investigations of shear and elongational flow properties of polystyrene melts reinforced with calcium carbonate, titanium dioxide, and carbon black

Abstract: Shear and elongational flow measurements on polystyrene melts reinforced with small particles were carried out. The influences of loading level, particle size and surface treatment on shear viscosity, principal normal stress difference, and elongational viscosity were discussed. These systems exhibited yield values for both shear and elongational flow. Experimental values for the ratio of the tensile to the shear yield stress give satisfactory agreement with the predictions of the von Mises yield criterion. The yield value appears to increase with decreasing particle size and may be varied with surface treatment. The principal normal stress difference at fixed shear stress decreases with volume loading of particulates. The results are interpreted in terms of a system forming a gel due to interparticle forces, which is disrupted by a critical distortional strain energy.

Materials Science Comparative Evaluation of Ceramic-metal Bond Tests Using Finite Element Stress Analysis

Abstract: Eleven porcelain-fused-to-metal bond tests were analyzed for interfacial shear stress distribution using finite-element stress analysis. Stress concentration effects are significant in ten of the 11 tests. A high probability of tensile failure within porcelain or the interfacial region was found in eight of the 11 tests analyzed.

Tensile properties and morphology of blends of polyethylene and polypropylene

Abstract: The tensile behavior of blends of linear polyethylene (PE) and isotactic polypropylene (PP) was examined in relation to their morphology. Yield stress increases monotonically with increasing PP content, while true ultimate strength is much lower in all blends than in the pure polymers as a result of early fracture. The blends fail at low elongation because of their two-phase structure, consisting of interpenetrating networks or of islands of PE in a PP matrix, as shown by scanning electron microscopy of fracture surfaces and transmission electron microscopy of thin films. While spherulites in PP are very large (∼100 μm in diameter), addition of 10% or more of PE drastically reduces their average size. This, together with the profusion of intercrystalline links introduced by PE, may be associated with maximization of tensile modulus in blends containing ∼80% PP. Introduction of special nucleating agents to PP reduces average spherulite size and is accompanied by slight improvements in modulus. Thin films of blends strained in the electron microscope neck and fibrillate in their PE regions, but fracture cleanly with little fibrillation in areas of PP.

Compression strength of carbon, glass and Kevlar-49 fibre reinforced polyester resins

Abstract: The compression behaviour of a series of polyester resins of various compositions and in different states of cure has been investigated. Their mechanical characteristics having been established, the same range of resins was then used as a matrix material for a series of composites reinforced with carbon, glass and aromatic polyamide fibres. The composites were unidirectionally reinforced, having been manufactured by pultrusion, and were compression tested in the fibre direction after a series of experiments to assess the validity of a simple testing procedure. “Rule of Mixtures” behaviour occurred in glass-polyester composites up to limiting volume fractions (V f) of 0.31 for strength and 0.46 for elastic modulus, the compression modulus being equal to the tensile modulus, and the apparent fibre strength being in the range 1.3 to 1.6 GPa at this limiting V f. At a V f of 0.31 the strengths of reinforced polyesters were proportional to the matrix yield strength, σ my, and their moduli were an inverse exponential function of σ my. For the same matrix yield strength a composite with an epoxy resin matrix was stronger than polyester based composites. At V f=0.30, Kevlar fibre composites behaved as though their compression modulus and strength were much smaller than their tensile modulus and strength, while carbon fibre composites were only slightly less stiff and weaker in compression than in tension. The compression strengths of the polyester resins were found to be proportional to their elastic moduli.

Tensile fracture of cancellous bone

Abstract: Excised specimens of cancellous bone from human femora were subjected to compressive or tensile testing, and the resulting force-displacement curves were recorded. The relationships between bone strength and apparent density were similar for specimens tested in these two loading modes. The modulus of elasticity was also comparable for the tensile and compressive specimens. Specimens loaded in compression absorbed considerable energy after the initial fracture because of progressive impaction of the trabeculae. In the specimens loaded in tension, the fractured bone fragments separated and therefore absorbed little additional energy after the initial failure. The energy absorption capacity was thus significantly lower for the tensile specimens. The results of this study show that the primary difference in mechanical properties of cancellous bone tested in tension and compression is the energy absorption capacity. This finding suggests that tensile and avulsion fractures of cancellous bone observed clinically are associated with minimal energy absorption and therefore may be precipitated by relatively minor trauma.

Morphology-property relationships in polycarbonate-based blends. II. Tensile and impact strength

Abstract: The tensile and Izod impact strength of polycarbonate (PC) based polyethylene (PE) and polystyrene (PS) blends has been examined. The tensile strength can best be described as being proportional to an exponential function of the volume fraction of PE and the first power of volume fraction of PS. The variation of Izod impact strength with composition also differs considerably for the two blends, a small amount of PS causing a marked drop in impact strength. The impact strength of the PE/PC blend is related to the area under the tensile stress-strain curve, whereas for PS/PC blends no correspondence is found. The variation in properties is related to the composition, morphology, interfacial adhesion at the phase boundary and failure surfaces of the various blends.

Material properties of femoral cancellous bone in axial loading. Part I: Time independent properties.

Abstract: The time independent material behavior of cylindrical specimens obtained from the cancelous bone of 20 cadaveric human femora were determined. In this part of the publication, the nominal values for compressive strength, limits of elasticity (yield point), strain, elastic modulus and apparent density are being reported for the cancellous bone of the femoral head and condyle. The correlations between the various parameters are analysed. A positive linear correlation between the four parameters compressive stength, limit of elasticity, modulus of elasticity and apparent density could not be excluded. The material properties vary considerably both within one single bone and between individuals. Compressive strength, modulus of elasticity and apparent density found for cancellous bone of the femoral head are greater than those found in the condyles. Within the condyles, compressive strength, elastic modulus and apparent density increase from the proximal parts to the parts closer to the joint. The medial femoral condyle showed higher compressive strength than the lateral one. Relating each of the three other parameters to the apparent density of the individual specimen did not result in equalizing the data for the material properties. This indicates that the mechanical properties of cancellous bone are strongly related to the direction of loading.

Degradation of tensile and shear properties of composites exposed to fire or high temperature

Abstract: The decrease in ultimate tensile strength, shear strength, tensile modulus, and shear modulus of fiber reinforced composites exposed to fire or to high temperature was investigated. A simple model was developed for calculating the mass loss of the material and the thickness of the char layer. The mass loss as well as the degradation in tensile and shear properties of Fiberite T300/1034 and Hercules AS/3501-6 graphite epoxy composites exposed to fire were measured. A correlation between the degradation in properties and the calculated mass loss and the char layer thickness was developed. A technique was proposed for predicting material damage through the use of such correlations.

Flaw Characteristics in Dynamic Fatigue: The Influence of Residual Contact Stresses

Abstract: The effect of residual contact stresses on the dynamic fatigue response of surfaces containing indentation-induced flaws is studied. Indentation fracture mechanics is used to analyze the growth of well-defined “median/radial” cracks in combined residual (elastic/plastic) contact and applied (uniform) tensile fields, and thence to determine strength characteristics. In this way a general formulation is obtained for the fatigue strength at constant stress rate. Experimental confirmation of the essential predictions of the theory is obtained from strength tests on Vickers-indented soda-lime glass disks in water environment. It is thereby implied that residual stresses can have a significant deleterious influence on the fatigue behavior of any brittle solid whose controlling flaws have a contact history. Such effects need to be considered in the design of structural ceramics, most notably where fracture-mechanics calibrations of crack-velocity parameters are used for lifetime predictions.

Process for making polymer filaments which have a high tensile strength and a high modulus

Abstract: A process for making polymer filaments which have a high tensile strength and a high modulus by stretching a polymer filament which contains an appreciable amount of polymer solvent at a temperature between the swelling point and the melting point of the polymer.

Maximum strength and drawing mechanism of hot drawn high molecular-weight polyethylene

Abstract: An investigation of the hot drawing of high molecular weight polyethylene fibres containing a substantial amount of solvent, and of fibres with a porous structure that were dried after solution spinning, was conducted. It was found that the tensile strength as well as the Young's modulus of the polyethylene fibres were linearly related to the applied stress up to values of 0.3 GPa. Drawing stresses exceeding 0.3 GPa could produce polyethylene fibres with a tensile strength of 3.7 GPa and a Young's modulus of 120 GPa. The ultimate mechanical properties appeared to be affected by the nature of the solvent, the polymer concentration and the spinning temperature. Chain extension in the hot drawing and the ultimate draw ratio depended substantially on the number of intermolecular entanglements initially present in the fibre.

The effect of porous surface configuration on the tensile strength of fixation of implants by bone ingrowth.

Abstract: In an attempt to gain information that could be directly applied to the design of clinical porous-surfaced prostheses intended for biological attachment by bone ingrowth, the tensile strength of the bone-implant interface was expressed as a function of 2 fundamentally different porous-surface configurations. Using powder metallurgy techniques, standard 3-hole fracture fixation plates were prepared with both a single and a multiple layer of spherically shaped metal powder particles on the bone-contacting surface to produce implants with different porous surfaces. These plates were implanted onto the lateral aspect of canine femurs for periods of 4, 6, 8, 12, 18, and 24 weeks. Mechanical tests were performed to measure the tensile strength of fixation of the implants by the ingrowth of bone. The results of the mechanical tests indicated that implants with the multiple particle layer surfce configuration develop a greater tensile strength of fixation than do implants with the single particle layer surface configuration. In addition, this fixation strength develops more quickly if the cortical bone is petaled prior to implantation. These findings should be considered when designing porous-surfaced implants intended for fixation by bone ingrowth.

The deformation of commercial aluminum-magnesium alloys

Abstract: The deformation and fracture of Al-Mg alloys have been investigated over a range of strain rates and temperatures. The rate and temperature-dependence of the deformation can be understood on the basis of the mobility of Mg atoms. When the Mg atoms can diffuse at a sufficient rate they interact with dislocations to produce serrated yielding and a zero or negative strain rate sensitivity. This greatly restricts the tensile ductility. Outside of this serrated flow regime enhanced ductilities are achieved due to the positive strain rate sensitivity stabilizing any inhomogeneities which develop. However, the final fracture is also influenced by the constituent particle concentration. Voiding occurs at particles and if the concentration of particles is sufficiently large the voids link up by local shear. Decreasing the constituent particle concentration, together with a reduction in the amplitude of serrations, results in larger tensile ductilities. At high temperatures, quite large strain rate sensitivities can be achieved but the ductility is finally limited by the propensity for voiding in these alloys.

Thermoplastic elastomer blends

Abstract: Thermoplastic elastomer compositions of the present invention comprise a blend of from about 10 to about 50 parts by weight of a crystalline 1-olefin polymer, from about 80 to about 15 parts by weight of a styrene-butadiene rubber, and from about 5 to about 55 parts by weight of a highly saturated elastomer. The thermoplastic blends have very good physical properties, especially tear strength, tensile strength, elongation at break, low temperature impact resistance, minimum creep at high temperatures, and smooth surfaces when injection molded. The compositions, which may be partially cured, also have excellent aging properties, as well as paint adhesion. The compositions are a true thermoplastic in that they can be repeatedly processed and yet maintain their good physical properties.

High tensile steel and process for producing the same

Abstract: A high tensile steel which has a satisfactory yield strength of 60 kg/mm2 or more and excellent resistances to sulfide corrosive cracking and corrosion, and which comprises, as indispensable components, 0.05 to 0.50 wt % of C, 0.1 to 1.0 wt % of Si, 0.1 to 2.0 wt % of Mn, 0.05 to 1.50 wt % of Co and the balance consisting of Fe, is produced by hot- or cold-rolling it, rapidly heating the rolled steel to austenitize it, quenching the austenitized steel and, finally, tempering the quenched steel at a temperature not higher than the Ac1 point of the steel.

Liquid nitrogen strengths of coated optical glass fibres

Abstract: The strengths of plastic-coated glass fibres have been measured at liquid nitrogen temperatures using a bending technique. The method yields data on the strengths of coated optical fibres in the absence of stress corrosion. Pristine strengths corresponding to a breaking strain of 21% have been measured for silica fibre and 12% for sodium borosilicate compound glass fibre, corrected to 50 cm gauge length. The low temperature strength was found to be directly related to the tensile strength measured at room temperature, and the relationship was valid for a variety of glass compositions with differing amounts of surface damage.

Analysis of pull-out tests on fibres embedded in brittle matrices

Abstract: A graphical interpretation and analysis of pull-out tests is developed to indicate combined effects of factors such as the tensile strength of the fibre and the bond characteristics of the fibre-matrix interfaces on the mode of pull-out failure. In addition to the critical embedment length the significance of two other embedment lengths is shown. One is the minimum length at which a tensile failure of a reinforcing element is not preceded by debonding and the other one is the maximum embedment length at which a complete debonding occurs instantaneously. The graphical analysis is applied to a typical pull-out test result and quantitative values of the ultimate elastic shear bond and the frictional bond are obtained.