Strength In Longitudinal Direction Research Articles

Mechanical Properties Study of Reinforced Thermoplastic Pipes Under A Tensile Load

This paper presents a study on the tensile properties of reinforced thermoplastic pipes (RTPs). A mechanical model of RTPs with an arbitrary number of reinforced layers under tensile action is constructed by combining the constitutive relationship of elastoplastic materials with the continuous displacement condition. On this basis, the effects of various parameters such as the winding angle, the number of structurally reinforced layers, and the inner polyethylene (PE) liner thickness on the tensile properties of the RTPs were analyzed, and a tensile test was carried out for validation. The results showed that the winding angle of the structurally reinforced layers was the main factor affecting an RTP’s tensile performance—decreases in the winding angle significantly improved its tensile ability, especially the longitudinal strength. With ±45° as the demarcation point, the winding angle smaller than ±45° will result in higher strength in longitudinal direction, and the lifting effect on RTP’s mechanical properties of the increasing number of reinforcement layers was better than that of the increasing thickness of the lining layer; when the winding angle was larger than ±45°, the opposite results were obtained. The fibre load was more sensitive to the winding angle than the PE load.

Investigation of Mechanical and Electromagnetic Interference Shielding Properties of Nickel–CFRP Textile Composites

The most common materials used for electromagnetic interference shielding are metals and their alloys. However, those materials are heavy and highly reflective. In order to eliminate or reduce the intensity of wave radiation in their working environment, lightweight materials that have interference shielding properties are needed. In this paper, nickel wire mesh yarns (warps) were woven into carbon fibers-reinforced plastic yarns (wefts) to produce metal–carbon textile composite materials. The plain weave and 2/2 twill weave techniques were used, and the woven fabrics were laminated to manufacture experimental test samples. The nickel, which has high magnetic permeability and good electric conductivity, and carbon fibers, which have good electrical, thermal and mechanical properties, were used together to achieve the desired properties. The shielding effectiveness of each sample was investigated using a network analyzer connected with coaxial transmission line test in accordance with ASTM 4935-99 standard, with the frequencies ranging from 500 MHz to 1.5 GHz. Here, the plain weave structure showed higher shielding effectiveness than twill weave. The absorption losses for both materials were relatively greater than reflection losses. In reference to the orientation of wire mesh yarns about the loading axis, the tensile strengths in the transversal direction were 19.04 and 16.34% higher than the tensile strengths in longitudinal direction for plain weave and twill weave, respectively. The fractography analysis with SEM showed a ductile fracture of wire mesh and brittle fracture of epoxy matrix and carbon fibers.

Effect of Crystallographic Texture on Anisotropy of Mechanical Properties in High Strength Martensitic Steel

The thermomechanical controlled processing (TMCP) is widely applied for one of the effective processes to improve strength and toughness of steel plates. In actual application, anisotropies of mechanical properties arising from crystallographic texture which is grown up in controlled rolling process are important issues. In this study the effect of texture on anisotropies of mechanical properties by experimentally manufactured YP960 MPa class steel plate was investigated. Strength varied through plate thickness from surface to mid-thickness. At surface, strength in longitudinal direction was higher than that in transverse direction, in contrast, strength in transverse direction was higher than that in longitudinal direction at mid-thickness. The major components of texture at plate surface were {110}<111> and {112}<111>, whereas those at mid-thickness were {332}<113> and {211}~{311}<011>. It is considered that the texture of plate surface was formed by shear strain in austenite region, and, that of mid-thickness was grown up by compressive strain. Crystal plasticity analysis based on texture information of the specimen revealed that the anisotropies of mechanical properties were strongly affected by microstructure orientation.

Tensile Strength, Elasticity and Cracking Character of Softwood Tissues

Wood tensile strength in longitudinal direction depends on wood density and structure. Growth rings in wood consist of earlywood and latewood which differ greatly in their properties. Latewood is denser, less porous and more resistant to tension along the fiber compared earlywod. The ratio of latewood and earlywood is different for each type of wood species and also depends on growing conditions, climate and etc. The study is aimed to evaluate the tensile strength, elasticity and cracking character of Lithuanian-grown softwood tissues, depending on the wood species, tissue width and latewood ratio in the sample. For the study three species of wood (spruce, pine and larch) were chosen. Samples were cut with the microtome, tissues cross-sectional area of about 0.15-0.50 mm2. The ratio of latewood and earlywood was evaluated using microscope. Wood tissue tensile strength was tested in the tensile machine with a feed rate of 0.2 mm/min. Research results showed that the highest tensile strength was obtained for larch wood samples, while the spruce wood most tended to deformation. Ir was determined that the tensile strength and elasticity of wood are highly influenced by wood microstructure and earlywood and latewood ratio in the sample. Also the wood microstructure and failure mechanism of the samples were evaluated. DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6881

Reliable test method for tensile strength in longitudinal direction of unidirectional carbon fiber-reinforced plastics

This article is concerned with the reliable test method for measuring the tensile strength in the longitudinal direction of unidirectional carbon fiber-reinforced plastics. A filament-wound resin-impregnated carbon fiber strand (carbon fiber-reinforced plastics strand) was employed as the specimen. The most important improvement for reliable tests is that the bonding strength of the end tabs with carbon fiber-reinforced plastics strand should be higher than the tensile strength of CFRP strand. We improved the bonding strength by co-curing the carbon fiber-reinforced plastics strand with end tabs. The improved method was applied to two kinds of carbon fiber-reinforced plastics strands and the reliable tensile strengths were obtained.

Understanding the interfacial compatibility and adhesion of natural coir fibre thermoplastic composites

An integrated physical–chemical–micromechanicalapproach is implemented to investigate the fibre–matrix interfacial compatibility and adhesion of natural coir fibre composites. Wetting measurements of the fibres and the matrices are carried out to obtain their static equilibrium contact angles in various liquids, and these are used to estimate the surface energies comprising of different components. The work of adhesion is calculated for each composite system, accordingly. Also, fibre surface chemistry is examined by X-ray photoelectron spectroscopy (XPS)to have more information about functional groups at the fibre surface, which assists in adeeper understand ing of the interactions at the composite interfaces. Single fibre pull-out tests and transverse three point bending tests are performed on UD composites to measure interfacial shear strength and interfacial tensile strength respectively. The results suggest that the higher interfacial adhesion of coir fibreswith polyvinyliden efluoridecompared with polypropylene can be attributed to higher fibre–matrix physico-chemical interaction corresponding with the work of adhesion. Whilst the improvement of interfacial adhesion for coir fibreswith maleic anhydride grafted polypropylene compared with polypropylene can probably be attributed to achemical adhesion mechanism. In agreement with the interface evaluations, the flexural strength in longitudinal direction of the composites is largely correlated with their interfacial adhesion.

Effects of welding-induced residual stress on ultimate strength of plates and stiffened panels

During the welding of steel-plated structures, geometric distortions and residual stresses are developed. The influence of welding-induced geometric distortions and residual stresses on the compressive ultimate strength in longitudinal direction of plates and stiffened panels were investigated using nonlinear finite element analyses considering a range of plate thicknesses with various levels of residual stresses. The residual stresses in plates and stiffened panels have been modelled carefully and their effects on these structures due to welding-induced imperfections only are studied. The results and insights observed from the current study are presented.

Mechanical behavior and failure process during compressive and shear deformation of honeycomb composite at elevated temperatures

The mechanical behavior and failure mechanism of honeycomb composite consisting of Nomex honeycomb core and 2024Al alloy facesheets were investigated. The compressive and shear deformation behaviors of honeycomb composite were analyzed at temperatures ranged 25–300°C. The compressive and shear strengths of honeycomb composite decreased continuously with increasing temperature up to 300°C. The stress-strain curves obtained from the compressive and shear tests showed that the stress increased to a peak value and then decreased rapidly to a steady state value, which is nearly constant up to failure with increasing strain. The compressive deformation behavior of honeycomb composite was progressed by an elastic and plastic buckling of cell walls, debonding fracture at the interfaces of cell walls, and followed by a fracture of resin layer on cell walls. The shear deformation of honeycomb composite was progressed by an elastic shear deformation, plastic shear deformation, fracture of resin layer on cell walls, and followed by debonding fracture at core/facesheet interfaces. The shear strength of honeycomb composite showed strong anisotropy dependent on the loading direction. The shear strength in longitudinal direction was about 1.4 times higher compared to that in transversal direction due to the different thickness of cell walls mainly loaded during the shear deformation.

STUDY ON SEGREGATION OF DIRECT CHILL CAST PURE ALUMINIUM SLABS IN EACH STAGE OF PRODUCTION OF THIN SHEETS

Direct Chill Casting of pure aluminium has special solidification process different from the Book Mold Casting.To acpuire the essential characteristics of Direct Chill Casting, the samples were taken from the standard slabs produced in commercial plant, and, in order of producing operation, the properties of molten metal, slab, hot rolled plate and cold rolled coil were studied systematically.The results of the studies on the relations of producing processes and on the residual effects of the preceding operations are as follows:1) Molten metal: Chemical composition is uniform at the holding stage.Mechanical properties are improved by holding and degassing, but at the first stage of pouring, are dateriorated temporarily and according to stabilization of operation come back to the improved state again.2) Slab: Macro-structure is fine and uniform except the part close to the sprue and other thin skin of the slab.Impurities of outer layer are very high, those of the layer from 2-10mm deep are lowest and those of the part deeper than 10mm are uniform which shows the mean value of the original molten metal.Hardness distribution is similar to that of composition.Tensile properties and impact value are uniform.Microstructure consists of three parts, namely, finely chilled part, slowly cooled part of columner structure, and granular, dendritic part in which “Schweb-kristall” is observed.We can't observe the periodic sweating and dark zone in which may not be able to exist in such slab made under the special casting control as this.3) Hot rolled plate:Segregation of surface in longitudinal or transverse direction is not recognized, but in thickness direction it exists due to the residual effect of the slab. Impurities are high at skin and low at center.Tensile strength in longitudinal direction is lower at central part due to the effect of different distribution of hot rolling temperature and cooling rate.Micro-structure in thickness direction differs remarkably at skin and center.4) Cold rolled coil: Local difference of chemical composition through the coil is neglisible. Tensile strength as rolled state is uniform in the coil, but after annealing it is lower at the center part of the coil. Grain size at center part is finer than outer part, which seems to be due to the residual effect of hot rolling condition.