Showing papers on "Ultimate tensile strength published in 2000"
TL;DR: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a "nanostressing stage" located within a scanning electron microscope and a variety of structures were revealed, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
Abstract: The tensile strengths of individual multiwalled carbon nanotubes (MWCNTs) were measured with a “nanostressing stage” located within a scanning electron microscope. The tensile-loading experiment was prepared and observed entirely within the microscope and was recorded on video. The MWCNTs broke in the outermost layer (“sword-in-sheath” failure), and the tensile strength of this layer ranged from 11 to 63 gigapascals for the set of 19 MWCNTs that were loaded. Analysis of the stress-strain curves for individual MWCNTs indicated that the Young's modulus E of the outermost layer varied from 270 to 950 gigapascals. Transmission electron microscopic examination of the broken nanotube fragments revealed a variety of structures, such as a nanotube ribbon, a wave pattern, and partial radial collapse.
5,011 citations
Book•
05 Oct 2000
TL;DR: Hardness measurements with conical and pyramidal indenters as mentioned in this paper have been used to measure the area of contact between solids and the hardness of ideal plastic metals. But they have not yet been applied to the case of spherical indenters.
Abstract: 1. Introduction 2. Hardness measurements by spherical indenters 3. Deformation and indentation of ideal plastic metals 4. Deformation of metals by spherical indenters. Ideal plastic metals 5. Deformation of metals by spherical indenters. Metals which work-harden 6. Deformation of metals by spherical indenters. 'Shallowing' and elastic 'recovery' 7. Hardness measurements with conical and pyramidal indenters 8. Dynamic or rebound hardness 9. Area of contact between solids Appendix I. Brinell hardness Appendix II. Meyer hardness Appendix III. Vickers hardness Appendix IV. Hardness conversion Appendix V. Hardness and ultimate tensile strength Appendix VI. Some typical hardness values
3,562 citations
TL;DR: The mechanical response of 15 single wall carbon nanotube (SWCNT) ropes under tensile load was measured and strain data were obtained and they broke at strain values of 5.3% or lower.
Abstract: The mechanical response of 15 single wall carbon nanotube (SWCNT) ropes under tensile load was measured. For 8 of these ropes strain data were obtained and they broke at strain values of $5.3%$ or lower. The force-strain data are well fit by a model that assumes the load is carried by the SWCNTs on the perimeter of each rope. This model provides an average breaking strength of SWCNTs on the perimeter of each rope; the 15 values range from 13 to 52 GPa (mean 30 GPa). Based on the same model the 8 average Young's modulus values determined range from 320 to 1470 GPa (mean 1002 GPa).
2,594 citations
TL;DR: Under unconstrained mechanical loading organized shear band patterns develop throughout the sample, which results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass.
Abstract: Results are presented for a ductile metal reinforced bulk metallic glass matrix composite based on glass forming compositions in the Zr-Ti-Cu-Ni-Be system. Primary dendrite growth and solute partitioning in the molten state yields a microstructure consisting of a ductile crystalline Ti-Zr-Nb b phase, with bcc structure, in a Zr-Ti-Nb-Cu-Ni-Be bulk metallic glass matrix. Under unconstrained mechanical loading organized shear band patterns develop throughout the sample. This results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass. PACS numbers: 81.40. – z, 81.05.Kf Zr41.2Ti13.8Cu12.5Ni10Be22.5 (V1) exhibits an exceptional bulk metallic glass (BMG) forming ability that has motivated investigations of its mechanical behavior [1– 3]. This alloy exhibits a 1.9 GPa tensile yield strength, and a 2% elastic strain prior to failure under tensile or compressive loading. However, as in all metallic glasses, V1 specimens loaded in a state of uniaxial or plane stress fail catastrophically on one dominant shear band and show little global plasticity. Specimens loaded under constrained geometries (plane strain) fail in an elastic, perfectly plastic manner by the generation of multiple shear bands. Multiple shear bands are observed when the catastrophic instability is avoided via mechanical constraint, e.g., in uniaxial compression, bending, rolling, and under localized indentation. This behavior under deformation has limited the application of bulk metallic glasses as an engineering material. This Letter presents results for a new class of ductile metal reinforced BMG matrix composites prepared via in situ processing. Under loading, the two-phase microstructure leads to spatial variations in elastic properties as well as the conditions for yielding, the ductile phase having a lower yield strain. The initiation and propagation of shear bands is controlled by the scale and geometry of the ductile phase dispersion with the result that deformation occurs through the development of highly organized patterns of regularly spaced shear bands distributed uniformly throughout the sample. The compositions in the Zr-Ti-Cu-Ni-Be system are compactly written in terms of a pseudoternary Zr-Ti-X phase diagram, where X represents the moiety Be9Cu5Ni4, characteristic of Zr41.2Ti13.8Cu12.5Ni10Be22.5. Results presented here are for alloys of the form Zr1002x2zTixMz1002yXy, where M is an element that stabilizes the crystalline b phase in Ti- or Zr-based alloys. The inset in Fig. 1 shows the x-ray diffraction pattern for the nominal composition Zr75Ti18.34Nb6.6675X25; i.e., an alloy with M Nb, z 6.66, x 18.34, and y 25. The diffraction pattern was obtained with an INEL diffractometer (Co-Ka radiation) on the cross sectioned surface of a 25 g arc melted rod of roughly cylindrical diameter, f 1 cm. The peaks shown [with (hkl) values labeled] are due to the bcc phase. A Nelson-Riley extrapolation yields a lattice parameter a 3.496 A [4]. Upon cooling from the high temperature melt, the alloy undergoes partial crystallization by nucleation and subsequent dendritic growth of the b phase in the remaining liquid. The remaining liquid subsequently freezes to the glassy state producing a twophase microstructure containing b-phase dendrites in a glass matrix. The final microstructure of a chemically etched specimen is shown in the scanning electron microscopy (SEM) image of Fig. 1. SEM electron microprobe analysis gives the average composition for the b-phase dendrites (light phase in Fig. 1) to be Zr 71Ti16.3Nb10Cu1.8Ni0.9. Under the assumption that all of the Be in the alloy is partitioned into the matrix we estimate that the average composition of the amorphous matrix (dark phase) is Zr47Ti12.9Nb2.8Cu11Ni9.6Be16.7. Both are quoted
1,365 citations
TL;DR: In this paper, the authors reviewed and analyzed the developments made during last few decades in the field of high performance carbon fibers and identified and suggested some specific areas for future research in order to minimize the gap between theoretical and practically realized tensile strengths and other mechanical properties of carbon fibers.
Abstract: An attempt has been made to review and analyze the developments made during last few decades in the field of high performance carbon fibers The focus is primarily on high technology sector, which includes aerospace and nuclear engineering or other areas, where the large scale use of carbon fibers is driven by maximum performance and not by cost factors We have identified and suggested some specific areas for future research in order to minimize the gap between theoretical and practically realized tensile strengths and other mechanical properties of carbon fibers
793 citations
TL;DR: In this article, the tensile properties of polypropylene (PP) reinforced with short glass fibers (SGF) and short carbon fibers (SCF) were investigated with extrusion compounding and injection molding techniques.
Abstract: Composites of polypropylene (PP) reinforced with short glass fibers (SGF) and short carbon fibers (SCF) were prepared with extrusion compounding and injection molding techniques. The tensile properties of these composites were investigated. It was noted that an increase in fiber volume fraction led to a decrease in mean fiber length as observed previously. The relationship between mean fiber length and fiber volume fraction was described by a proper exponential function with an offset. The tensile strength and modulus of SGF/PP and SCF/PP composites were studied taking into account the combined effect of fiber volume fraction and mean fiber length. The results about the composite strength and modulus were interpreted using the modified rule of mixtures equations by introducing two fiber efficiency factors, respectively, for the composite strength and modulus. It was found that for both types of composites the fiber efficiency factors decreased with increasing fiber volume fraction and the more brittle fiber namely carbon fiber corresponded to the lower fiber efficiency factors than glass fiber. Meanwhile, it was noted that the fiber efficiency factor for the composite modulus was much higher than that for the composite strength. Moreover, it was observed that the tensile failure strain of the composites decreased with the increase of fiber volume fraction. An empirical but good relationship of the composite failure strain with fiber volume fraction, fiber length and fiber radius was established.
717 citations
TL;DR: In this paper, axial compression test results of 27 concrete cylinders confined by carbon fiber reinforced polymer composite jackets were described, and the failure of the confined concrete was dominated by the rupture of the jacket at an average strain much smaller than the ultimate strain obtained from tension tests of flat coupons.
Abstract: This paper describes axial compression test results of 27 concrete cylinders confined by carbon fiber reinforced polymer composite jackets. The experimental parameters include plain concrete compressive strength and the thickness of the composite jacket. It is found that the carbon fiber composite jacketing can significantly increase the compressive strength and ductility of concrete. The test results indicate that concrete strength and confinement modulus, defined as the ratio of transverse confinement stress and transverse strain, are the most influential factors affecting the stress-strain behavior of confined concrete. The failure of the confined concrete was dominated by the rupture of the jacket at an average strain much smaller than the ultimate strain obtained from tension tests of flat coupons. In order to describe the main mechanical features of the confined concrete, a simple bilinear stress-strain model is suggested based on the theory of elasticity and minimum number of empirical equations de...
661 citations
TL;DR: In this paper, the effect of pore size distribution on the drying shrinkage of slag concrete has been investigated, and it was found that the pore sizes within the mesopore region were a more important parameter in determining the magnitude of shrinkage, rather than the amount of moisture loss.
486 citations
TL;DR: In this article, tensile strength, modulus of rupture, and impact resistance were found for different layer orientations of ABS rapid prototype solid models, fabricated by a Stratasys rapid prototyping machine.
Abstract: Tensile strength, modulus of rupture, and impact resistance were found for different layer orientations of ABS rapid prototype solid models. The samples were fabricated by a Stratasys rapid prototyping machine in five different layer orientations. The 0° orientation where layers were deposited along the length of the samples displayed superior strength and impact resistance over all the other orientations. The anisotropic properties were probably caused by weak interlayer bonding and interlayer porosity.
477 citations
TL;DR: Anisotropic FE-models of the femur could be realized for most part with the summarized material properties of bone if characterized by apparent density and load directions, but several mechanical properties have not been correlated to these main criteria.
440 citations
TL;DR: These findings establish that, once effective tissue modulus is calibrated and uniform but asymmetric tissue failure strains are used, the resulting models can capture the apparent strength behavior to an outstanding level of accuracy.
TL;DR: In this article, the effect of fiber coating on the interface properties has also been investigated, including tensile and flexural performance of the composites and failure behavior of the failure behavior.
Abstract: Oil palm fibres have been used as reinforcement in phenol formaldehyde resin. In order to improve the interfacial properties, the fibres were subjected to different chemical modifications such as mercerisation, acrylonitrile grafting, acrylation, latex coating, permanganate treatment, acetylation, and peroxide treatment. The effect of fibre coating on the interface properties has also been investigated. Morphological and structural changes of the fibres were investigated using scanning electron microscopy and IR spectroscopy. Mechanical properties of untreated and treated fibres were studied. Changes in stress–strain characteristics, tensile strength, tensile modulus and elongation at break of the fibres upon various modifications were studied and compared. The incorporation of the modified fibres resulted in composites having excellent impact resistance. Fibre coating enhanced the impact strength of untreated composite by a factor of four. Tensile and flexural performance of the composites were also investigated. Finally, inorder to have an insight into the failure behaviour, the tensile and impact fracture surfaces of the composites were analysed using scanning electron microscope.
TL;DR: In this paper, surface modifications of two varieties of jute fabrics, i.e. hessian cloth (HC) and carpet backing cloth (CBC), involving dewaxing, alkali treatment, cyanoethylation and grafting, have been made with a view to their use as reinforcing agents in composites based on a biodegradable polymeric matrix, Biopol.
TL;DR: In this article, the optimization of fiber size, fibre content, and fly ash content in hybrid polypropylene-steel fiber concrete with low fibre content based on general mechanical properties was investigated.
TL;DR: In this article, equal channel angular (ECA) pressing at room temperature was used to reduce the grain sizes of six commercial aluminum-based alloys (1100, 2024, 3004, 5083, 6061, and 7075) to within a submicrometer range.
Abstract: Using equal-channel angular (ECA) pressing at room temperature, the grain sizes of six different commercial aluminum-based alloys (1100, 2024, 3004, 5083, 6061, and 7075) were reduced to within the submicrometer range. These grains were reasonably stable up to annealing temperatures of ∼200 °C and the submicrometer grains were retained in the 2024 and 7075 alloys to annealing temperatures of 300 °C. Tensile testing after ECA pressing through a single pass, equivalent to the introduction of a strain of ∼1, showed there is a significant increase in the values of the 0.2 pct proof stress and the ultimate tensile stress (UTS) for each alloy with a corresponding reduction in the elongations to failure. It is demonstrated that the magnitudes of these stresses scale with the square root of the Mg content in each alloy. Similar values for the proof stresses and the UTS were attained at the same equivalent strains in samples subjected to cold rolling, but the elongations to failure were higher after ECA pressing to equivalent strains >1 because of the introduction of a very small grain size. Detailed results for the 1100 and 3004 alloys show good agreement with the standard Hall-Petch relationship.
TL;DR: In this article, a study of Haliotis rufescens (abalone) shells was carried out and the authors found that the abalone shell exhibited orientation dependence of strength, as well as significant strain-rate sensitivity; the failure strength at loading rates between 10×103 and 25×103 GPa/s was approximately 50% higher than the quasi-static strength.
TL;DR: In this paper, soundly aligned single-walled carbon nanotube (SWNT) ropes, synthesized by the catalytic decomposition of hydrocarbons, were employed for direct tensile strength measurements.
Abstract: 20 mm long ropes consisting of soundly aligned single-walled carbon nanotube (SWNT) ropes, synthesized by the catalytic decomposition of hydrocarbons, were employed for direct tensile strength measurements. The average tensile strength of SWNT rope composites is as high as 3.6 +/-0.4 GPa, similar to that of carbon fibers. The tensile strength of SWNT bundles was extrapolated from the strength of the composites to be 2.3 +/-0.2 to 14.2 +/-1.4 GPa after simply taking into account the volume fraction of SWNT bundles in the minicomposite, and the tensile strength of single SWNTs was estimated to be as high as 22.2 +/-2.2 GPa. The excellent mechanical properties of SWNTs will make them an ideal reinforcement agent for high performance composite materials. (C) 2000 American Institute of Physics. [S0003- 6951(00)00546-5].
Journal Article•
TL;DR: A durable resin bond strength to yttrium-oxide-partially-stabilized zirconia ceramic (YPSZ) was achieved only after air abrasion of YPSZ and using one of two resin composites containing a special phosphate monomer.
Abstract: Purpose The aim of this in vitro study was to evaluate the long-term bond strength of adhesive bonding systems to yttrium-oxide-partially-stabilized zirconia ceramic (YPSZ). Materials and methods Plexiglas tubes filled with resin composite were bonded to industrially manufactured zirconia ceramic disks (96% ZrO2 stabilized by 4% Y2O3). After air abrading the ceramic and ultrasonic cleansing, groups of 16 samples were bonded in an alignment apparatus using 7 different bonding methods. Subgroups of 8 bonded samples were tested for tensile strength following storage in distilled water at 37 degrees C either for 3 days or 2 years. In addition, the 2-year samples were thermocycled 37,500 times. The statistical analyses were conducted with the Kruskal-Wallis test followed by multiple pair-wise comparison of the groups using the Wilcoxon rank sum test. Results A moderate to relatively high initial bond strength was achieved by air abrasion alone, the additional use of a silane, or acrylizing the YPSZ surface in combination with a conventional bis-GMA resin composite. However, these methods failed spontaneously over storage time. The use of the bis-GMA resin composite after tribochemical silica coating of YPSZ and the use of a polyacid-modified resin composite after air abrasion of YPSZ resulted in a high initial bond strength which decreased significantly over storage time. A durable resin bond strength to YPSZ was achieved only after air abrasion of YPSZ and using one of two resin composites containing a special phosphate monomer. Conclusion A durable bond strength to YPSZ was achieved only by using resin composites containing a special adhesive monomer.
TL;DR: In this paper, various combinations of a local natural pozzolan and silica fume were used to produce workable high to very high strength mortars and concretes with a compressive strength in the range of 69-110 MPa.
Abstract: Various combinations of a local natural pozzolan and silica fume were used to produce workable high to very high strength mortars and concretes with a compressive strength in the range of 69–110 MPa. The mixtures were tested for workability, density, compressive strength, splitting tensile strength, and modulus of elasticity. The results of this study suggest that certain natural pozzolan–silica fume combinations can improve the compressive and splitting tensile strengths, workability, and elastic modulus of concretes, more than natural pozzolan and silica fume alone. Furthermore, the use of silica fume at 15% of the weight of cement was able to produce relatively the highest strength increase in the presence of about 15% pozzolan than without pozzolan. This study recommends the use of natural pozzolan in combination with silica fume in the production of high strength concrete, and for providing technical and economical advantages in specific local uses in the concrete industry.
TL;DR: Adhesion to dental hard tissues after Er:YAG laser etching is inferior to that obtained after conventional acid etching and extensive subsurface fissuring that is unfavorable to adhesion is shown.
Abstract: Statement of Problem. Er:YAG (erbium-doped yttrium aluminium garnet) lasers have been effective in the removal of dental tissues. It has been suggested that they are also useful for preparing dental surfaces for adhesion, but results to date have been controversial. Purpose. This study compared the tensile strength of bracket-tooth bonds obtained after preparation of the surface for adhesion (dentin or enamel) by conventional acid-etching or by Er:YAG laser etching and investigated microstructure of resin-tooth interfaces using the 2 procedures. Material and Methods. Eighty healthy human premolars were used. Brackets were cemented to acid-etched enamel, laser-etched enamel, acid-etched dentin, or laser-etched dentin (20 teeth per group). Dentin was previously exposed using a high-speed handpiece. Acid-etching was with 37% orthophosphoric acid (15 seconds for enamel, 5 seconds for dentin). Laser etching was with Er:YAG laser (four 200 mJ pulses per second for enamel; four 160 mJ pulses per second for dentin). Brackets were bonded with autocuring resin paste, having first applied a primer (dentin only) and then light-cured bonding resin. Tensile strength was determined with a universal testing machine. Data were analyzed with 2-way ANOVA and subsequent t test with Bonferroni correction. Fracture patterns were compared by the Wilcoxon test with Bonferroni correction. For SEM studies of the resin-tooth interface, a total of 12 premolars were used (3 for each tissue per treatment combination). Results. Mean tensile bond strength for acid-etched enamel (14.05 ± 5.03 MPa) was significantly higher ( P P Conclusion. Adhesion to dental hard tissues after Er:YAG laser etching is inferior to that obtained after conventional acid etching. Enamel and dentin surfaces prepared by Er:YAG laser etching show extensive subsurface fissuring that is unfavorable to adhesion. (J Prosthet Dent 2000;84:280-8.)
TL;DR: In this paper, the authors examined the properties of gellan films as a function of glycerol concentration and found that adding more than 75% glycerols to gellans increased extensibility, but decreased tensile strength, elastic modulus and T g, and increased WVP.
TL;DR: In this paper, chemical surface modifications of jute fabrics involving bleaching, dewaxing, alkali treatment, cyanoethylation and vinyl grafting are made in view of their use as reinforcing agents in composites based on a biodegradable polyester amide matrix, BAK 1095.
Abstract: The chemical surface modifications of jute fabrics involving bleaching, dewaxing, alkali treatment, cyanoethylation and vinyl grafting are made in view of their use as reinforcing agents in composites based on a biodegradable polyester amide matrix, BAK 1095. The effect of different fibre surface treatments and fabric amounts on the performance of resulting composites are investigated. The mechanical properties of composites like tensile and bending strengths increase as a result of surface modification. Among all modifications, alkali treatment and cyanoethylation result in improved properties of the composites. The tensile strength of BAK is increased by more than 40% as a result of reinforcement with alkali treated jute fabrics. SEM investigations show that the surface modifications improve the fibre–matrix interaction. From degradation studies we find that after 15 days of compost burial about 6% weight loss is observed for BAK whereas cyanoethylated and alkali treated jute–BAK composites show about 10% weight loss. The loss of weight as well as the decrease of bending strength of degraded composites is more or less directly related.
TL;DR: In this paper, a novel noncontact strain measurement technique has been employed to measure the tensile properties of extremely small "microsamples" of pure high-density ultrafine-grained Al (ufg-Al) nanocrystalline Cu (n-Cu) and n-Ni, which confirmed the absence of Young's modulus variations for metals with grain sizes approaching 25 nm.
Abstract: A novel non-contact strain measurement technique has been employed to measure the tensile properties of extremely small ‘microsamples’ of pure high-density ultrafine-grained Al (ufg-Al) nanocrystalline Cu (n-Cu) and nanocrystalline Ni (n-Ni). These microsample tests confirmed the absence of Young's modulus variations for metals with grain sizes approaching 25 nm. Significant strength enhancements were associated with the nanocrystalline specimens; the tensile stresses achieved in these microsample tests were measured to be an appreciable fraction of the theoretical shear strength for these metals. The ufg-Al samples (diameter, 250 nm) exhibited extensive plasticity while deformation in the n-Ni (diameter, 28 nm) remained almost entirely elastic up to failure at 1500MPa. The n-Cu samples were found to have a multiscale grain structure that produced an attractive balance of strength and ductility. Transmission electron microscopy investigations of deformed n-Ni failed to produce any evidence of dis...
TL;DR: In this article, the influence of fiber length and fiber content on stiffness, strength and impact strength of natural-fibre-mat-reinforced thermoplastics (NMTs) is reported and compared with data for glass-mat reinforced thermoplastic composites (GMTs).
Abstract: Thermoplastic composites based on flax fibres and a polypropylene (PP) matrix were manufactured using (i) a film-stacking method based on random fibre mats and (ii) a paper making process based on chopped fibres. The influence of fibre length and fibre content on stiffness, strength and impact strength of these so-called natural-fibre-mat-reinforced thermoplastics (NMTs) is reported and compared with data for glass-mat-reinforced thermoplastics (GMTs), including the influence of the use of maleic-anhydride grafted PP for improved interfacial adhesion. In addition some preliminary data on the influence of fibre diameter on composite stiffness and strength is reported. The data is compared with the existing micro-mechanical models for strength and stiffness. A good agreement was found between theory and experiment in case of stiffness whereas in the case of strength the experimental values fall well below the theoretical predictions. Results indicated that NMTs are of interest for low-cost engineering applications and can compete with commercial GMTs when a high stiffness per unit weight is desirable. Results also indicated that future research towards significant improvements in tensile and impact strength of these types of composites should focus on the optimisation of fibre strength rather than interfacial bond strength.
15 Feb 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the influence of rear earths (RE) on the microstructure of AZ91 and Mg-6Al-xRE magnesium alloys was investigated, where x is 0, 1, 2 and 3% (in weight percent, wt%), respectively.
Abstract: AZ91–xRE and Mg–6Al–xRE magnesium alloys were studied, where x is 0, 1, 2 and 3% (in weight percent, wt.%), respectively. Influence of rear earths (RE) on the microstructure was investigated. Fine morphology could be achieved by high cooling rate. By casting fluidity spiral specimens, fluidities of the alloys were achieved. The hardness and microhardness of the alloys was tested. RE improved fluidity and hardness. By casting specimens in permanent mold, tensile properties of the alloys with different RE additions at ambient and elevated temperatures were studied. RE had little effect on ambient temperature tensile strength of AZ91 alloy but greatly improved that of Mg–6Al alloy and high temperature tensile properties of both alloys. The fracture behavior of the alloys, which was changed by RE and high temperature, was examined by scanning electron microscopy (SEM) and optical microscopy. Fracture of the alloys is predominantly brittle cleavage or/and quasi-cleavage failure.
15 Jan 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the tensile properties of Mg-30 vol.% SiC particle composite are evaluated at room and elevated temperatures (up to 400°C). And the composites in the as-cast conditions do not show any change in dendrite arm spacing compared to unreinforced pure magnesium.
Abstract: Pure magnesium-30 Vol.% SiC particle composite are fabricated by melt stir technique without the use of a flux or protective inert gas atmosphere. After hot extrusion with an extrusion ratio of 13, Mg-30 vol.% $SiC_P$ composites have been evaluated for their tensile properties at room and elevated temperatures (up to 400°C). Composites in the as-cast conditions do not show any change in dendrite arm spacing:cell size compared to unreinforced pure magnesium. However, in the extruded conditions average grain size of the composites is 20 mm compared to 50 mm in the pure magnesium. Microstructure shows no evidence of reaction product at particle:matrix interface. At room temperature, stiffness and UTS of the extruded composites are 40 and 30% higher compared to unreinforced pure magnesium, signifying significant strengthening due to the presence of the SiC particles. Further, up to temperatures of 400°C, composites exhibit higher UTS compared to pure magnesium. Mg composites show a wear rate lower by two orders of magnitude compared to pure Mg, when tested against steel disc using pin-on disc machine.
TL;DR: In this article, the effect of cooling rate on the fiber-matrix interface adhesion for a carbon fiber/semicrystalline polyetheretherketone (PEEK) composite was characterised based on the fibre fragmentation, fibre pullout and short beam shear tests.
Abstract: The effect of cooling rate on the fibre–matrix interface adhesion for a carbon fibre/semicrystalline polyetheretherketone (PEEK) composite was characterised based on the fibre fragmentation, fibre pullout and short beam shear tests. The interface adhesion was correlated to the degree of crystallinity and the crystalline morphology, as well as the bulk mechanical properties of neat PEEK resin, all of which were in turn controlled by cooling rate. It was shown that the interface bond strength decreased with increasing cooling rate; the tensile strength and elastic modulus of PEEK resin decreased, while the ductility increased with increasing cooling rate through its dominant effect on crystallinity and spherullite size. The improvement of crystalline perfection and flattened lamella chains with high crystallinity at the interphase region were mainly responsible for the strong interface bond in composites processed at a low cooling rate. The interphase failure was characterised by brittle debonding in slow-cooled composites, whereas the amorphous PEEK-rich interphase introduced in fast cooled specimens failed in a ductile manner with extensive plastic yielding.
Book•
01 Jan 2000
TL;DR: In this article, the typical mechanical properties of Wrought and cast aluminum alloys at various temperatures are described. Butler et al. show that the tensile properties at subzero temperature, at temperature after various holding times at the test temperature, and at room temperature after exposure at various times at different temperatures stresses required to generate various amounts of creep in various lengths of time rotating-beam fatigue strengths.
Abstract: Contents include: Typical Mechanical Properties of Wrought and Cast Aluminum Alloys at Various Temperatures - tensile properties at subzero temperature, at temperature after various holding times at the test temperature, and at room temperature after exposure at various temperatures for various holding times creep rupture strengths for various times at various temperatures stresses required to generate various amounts of creep in various lengths of time rotating-beam fatigue strengths modulus of elasticity as a function of temperature Fatigue Data - fatigue strength of wrought aluminum alloys (approximate average values as determined in tests of smooth and notched rotating-beam fatigue machines), axial stress fatigue strength of wrought aluminum alloys (at various stress ratios, smooth and notched specimens), average fatigue strength for aluminum and aluminum alloy flat sheet specimens (under complete reversed flexure), cantilever-beam fatigue test results of aluminum alloys at elevated temperatures following stabilization at the test temperature.
TL;DR: In this paper, the quasi-static and impact properties of a novel fiber/metal laminate system based on a tough glass-fibre-reinforced polypropylene (GFPP) are investigated.
TL;DR: In this paper, the effect of steel corrosion on the structural behavior of reinforced concrete structural elements in their service and ultimate states has been investigated on fourteen-year-old reinforced concrete beams, on two control elements and two corroded beams.
Abstract: Steel corrosion in reinforced concrete leads to crack occurrence along the reinforcement (secondary cracks), to a reduction in bond strength and a reduction in steel cross section. The purpose of this study is to determine the effect of these deteriorations on the global behaviour of reinforced concrete structural elements in their service and ultimate states. Mechanical experimentation was carried out on fourteen-year-old reinforced concrete beams, on two control elements and two corroded beams. A comparative analysis of the results obtained on the beams showed that concrete cracking in the compressive area had no significant influence on the behaviour in service of the corroded elements. However, significant modifications of service behaviour were observed, due to the degradations in the tensile zone, namely: loss of bending stiffness, dissymmetrical behaviour. Finally, the measure of the residual steel cross-section of the corroded re-bars showed that the loss of bending stiffnes due to steel corrosion cannot be merely explained in terms of steel cross-section reduction. Concerning the ultimate behaviour, the loss of steel cross-section is the main parameter which leads to a reduction of bearing capacity and ductility. Another part will explain the separate and coupling effects of bond strength and steel cross-section loss on the mechanical behaviour of corroded beams.