Hoop Tensile Strength Research Articles

Joint effects of rotational extrusion and TiO2 on performance and antimicrobial properties of extruded polypropylene copolymer pipes

ABSTRACTIn this study, effects of titanium dioxide (TiO2) and rotation extrusion on structures and properties of polypropylene random copolymer (PPR) pipes were investigated. The experimental results showed that with the presence of TiO2, not only the antibacterial ability of PPR pipe was improved significantly but also the toughness was enhanced since a large number of PP chains were promoted to crystallize into β‐form crystals. Furthermore, when rotation extrusion was introduced into the process of PPR pipe, the drag hoop flow caused by mandrel and die rotation was superposed on the axial flow, so the polymer melts in the annulus underwent a helical flow and its flow direction deviated from the axis to drive the molecular orientation off the axial direction, bringing out the increased hoop strength. As a result, PPR pipe with excellent performance was prepared under the combined effect of rotation extrusion and TiO2. The antibacterial activity was 99.2%, the hoop tensile strength reached 27.5 MPa, 67.7% higher than that of the convention‐extruded PPR pipe with TiO2, and the impact strength was 10.9 kJ/m2, increased by 81.6% compared to that of the rotation‐extruded pure PPR pipe. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42410.

Investigation of the C-ring test for measuring hoop tensile strength of nuclear grade ceramic composites

Silicon carbide (SiC) and silicon carbide fiber reinforced composites (SiC/SiCf) are currently being evaluated as a high temperature material for use in nuclear reactors. While methods to determine the mechanical properties of SiC/SiCf on planar test specimens are well established, mechanical testing methods for tubular SiC/SiCf are still being developed. In this study the C-ring test is evaluated for use with nuclear grade SiC/SiCf as a method of measuring hoop strength. For the samples tested in this work, hoop strengths from C-ring testing are shown to agree within 6% to those obtained using expanding plug testing and analysis shows that the expected composite behavior is observed during testing. While other techniques may give more accurate values for hoop stress, the small specimen requirements and ease of testing makes C-ring testing a valuable tool.

Improving the Performance of Reprocessed ABS Products from the Manufacturing Perspective via the Taguchi Method

Additives are costly and can have negative environmental effects. Thus, searching for other alternatives to improve recycling plastics without using additives is necessary. This study aims to improve the hoop tensile strength, elongation at break, and shrinkage of the ring stopper made from an acrylonitrile butadiene styrene blend comprising 40% recyclates through the optimization of processing parameters using the Taguchi method. By adopting the L9 Taguchi orthogonal array, four controllable factors each at three levels are tested to determine the optimal combination of factors and levels in the injection moulding process. Considering the multiple quality characteristics involved in this study, we investigate the effects of processing parameters on hoop tensile strength, elongation at break, and shrinkage of the ring stopper both separately and simultaneously because changing a parameter can result in the improvement or deterioration of each quality response and of the overall product performance. The results revealed that the performance of an injection-moulded ring stopper under the optimal process conditions is equivalent or slightly better than that of the part produced from virgin resin. The performance of recycled plastics can be effectively enhanced to levels comparable with virgin resins using the Taguchi optimization approach.

Experimental Investigation and Finite Element Analysis of Filament Wound GRP Pipes for Underground Applications

The filament winding process involving the manufacturing of composite pipes has better mechanical properties. However a number of influencing parameters may affect its mechanical behavior, which arises mainly due to its inherent property of anisotropy. In order to overcome this, many researches are progressing to optimize the process. In this paper an experimental investigation considering four process parameters and their subsequent study on the effects of the mechanical properties of filament wound Glass Reinforced Plastic (GRP) pipes was conducted. Nine 500mm pipes were manufactured based on Taguchi's Design of Experiments (DOE) Model and studied for optimization of axial tensile strength, hoop tensile strength and pipe stiffness using Taguchi's Robust Design. Analysis of Variance (ANOVA) method was also used to statistically determine the weight of each process variable on the particular response and a finite element analysis was performed using multi-layer elements for the optimized conditions to have a more realistic view of, how the pipe would behave in the operational scenario.

Apparent hoop tensile strength prediction of glass fiber-reinforced polyester pipes

The apparent hoop tensile strength of glass fiber-reinforced polyester pipes plays an important role during their design procedure. In some cases, glass fiber-reinforced polyester pipes industry used hydraulic failure pressure to obtain this value. In addition to the expensive and time-consuming characteristics of this experiment, it underestimates the apparent hoop tensile strength. A sequential failure modelling is developed to predict apparent hoop tensile strength modelling integrating classical lamination theory and progressive damage modelling. Developed modelling takes into account influence of incorporated sand layer in glass fiber-reinforced polyester pipe wall construction. Experimental study is conducted to validate developed technique. A very good agreement is observed between experimentally measured apparent hoop tensile strength of glass fiber-reinforced polyester pipes and predicted values employing sequential failure modelling.

Development and characterization of composite materials for production of composite risers by filament winding

Industry has been challenged to provide riser systems which are more cost effective and which can fill the technology gaps with respect to water depth, riser diameter and high temperatures left open by flexibles, steel catenary risers (SCRs) and hybrid risers. Composite materials present advantages over conventional steel risers because composite materials are lighter, more fatigue and corrosion resistant, better thermal insulators and can be designed for improving the structural and mechanical response. This paper contains a study of the toughening mechanism of an epoxy resin under rubber addition by means of fractographic analysis and its relation with the fracture process and increase of strength of a composite riser employing this polymeric matrix. Initially, an epoxy resin system was toughened by rubber CTBN addition (10 wt. (%)) as a way of improving the flexibility of future risers. Mechanical and thermal analyses were carried out for characterizing the polymeric systems. Later, composite tubes were prepared and mechanically characterized. The influence of matrix toughening on the mechanical behavior of the tubes was also studied. Split-disk tests were used to determine the hoop tensile strength of these specimens. The results indicate that the matrix plays an important role in composite fracture processes. The adding rubber to the polymeric matrix promoted a simultaneous increase of stress and elongation at fracture of the tubes manufactured herein, which is not often reported. These results, probably, is function of better adhesion between fibers and polymeric matrix observed in the CTBN-modified composite rings, which was evidenced in the fractografic analysis by SEM after the split-disk tests.

Long-Term Performance of GFRP Tubes Filled with Concrete and Subjected to Salt Solution

AbstractThis paper presents mechanical, microstructural, and physical characterization of aged glass fiber-reinforced polymer (GFRP) tubes used in the concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) system for bridge columns and marine pile applications, or used hollow as tubular poles or in pipelines. The main objective of the study is to evaluate the durability and predict the long-term behavior of the filament-wound GFRP tubes. CFFTs were exposed to salt solution at 23, 40, and 50°C for 365 days to accelerate the environmental effect. Given the significance of confinement in a CFFT system, the measured hoop tensile strength of the tube before and after exposure was considered the primary indicator of durability performance of the specimens. In addition, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were used to characterize the aging effect on GFRP tubes. Test results showed that the GFRP tubes investigated in ...

Morphology and property of polyethylene pipe extruded at the low mandrel rotation

AbstractDuring the rotation extrusion of polyethylene (PE) pipes, with the rotating mandrel, compressed air as a cooling medium was introduced through their interior to achieve the quick cooling of the inner wall. The experimental results showed that the hoop stress exerted by mandrel rotation could promote the molecular orientation in the hoop direction; moreover, the introduction of compressed air could quicken its inner wall's cooling rate so as to slow down the relaxation of the oriented molecule and to reserve the orientation structure. Therefore, the hoop orientation degree increased with the increasing inner wall's cooling rate. As a result, the performance of the PE pipe was greatly enhanced. The hoop tensile strength of the PE pipe produced by the novel extrusion method increased from original 24.1 MPa up to 35 MPa; the pipe's crack initiation time increased from 27 to 60 h and the crack growth rate slowed down. POLYM. ENG. SCI., 50:1743–1750, 2010. © 2010 Society of Plastics Engineers

FRP tube encased rubberized concrete cylinders

In this study, FRP tube encased waste tire rubber modified concrete cylinders were investigated. Four batches of confined and unconfined concrete cylinders with a diameter of 101.6 mm and a height of 304.8 mm were prepared. Each batch contained three confined cylinders and three unconfined cylinders. The total number of effective cylinders prepared was 24. Batches 1–3 were made of rubberized concrete. In Batch 1, 15% by volume of coarse aggregate was replaced by waste tire fibers or stripes; in Batches 2 and 3, 15% by volume of sand and 30% by volume of sand were replaced by crumb rubbers, respectively. Batch 4 was a control batch with conventional plain concrete. Uniaxial compression tests were conducted on all the cylinders per ASTM C39. Strain gages were installed on the encased rubberized concrete cylinders to obtain local strain distributions. The compressive strength and strain at the peak load were compared with the predictions by available design-oriented confinement models. It is found that the FRP tube encased rubberized concrete cylinders have higher confinement effectiveness, ductility, and elastic regions than FRP tube encased conventional concrete cylinders. Waste tire fiber modified concrete performs better than crumb rubber modified concrete with a lower cost. Instead of volume contraction, FRP encased rubberized concrete cylinders experience volumetric expansion. The current design-oriented confinement models cannot consistently predict the compressive strength and strain of the encased cylinders. An 1-D coupon test cannot uniquely determine the hoop tensile strength of the FRP tubes which are subjected to a 2-D stress condition.

Effects of the strength and precision properties of filament winding epoxy pipes

Behavior of fiber reinforced composite pressure vessels has been analyzed and developed theoretically. Winding angle and temperature are two kinds of effect factors on filament wound composite pressure vessels. FEM method, elastic solution procedure based on Lekhnitskii's theory and thickwalled theory were employed to verify the optimum winding angles. The aim of this study was to investigate processing parameters of continuous fiber reinforced epoxy composite pipes produced by the filament winding technique. For this purpose, two kinds of tests were performed for the specimen produced with two different methods, five different winding angles and five different curing temperatures. By determining the hoop tensile strength and precision, the winding angle, thermal properties and fitting temperature were evaluated. It is found that use of winding angles greater than 55° increases the performance of the structures considerably. It is also concluded that the use of the curing temperature of 150°C can increase the precision properties during the curing processing than other temperature conditions; at the same time, time of curing course also is an important effect factor to precision quality.

Use of split-disk tests for the process parameters of filament wound epoxy composite tubes

The aim of this study was to investigate processing parameters of continuous fiber reinforced epoxy composite tubes produced by the filament winding technique. For this purpose, split-disk tests (according to ASTM D-2290 standard) were performed for the specimens produced with two different epoxy resin systems, five different fiber materials and five different winding angles. By determining the hoop tensile strength and modulus of these specimens, the effects of three filament-winding processing parameters; resin type, fiber type and winding angle were evaluated. It is found that use of different epoxy resin systems has no significant influences, while use of carbon fibers compared to glass fibers and use of winding angles greater than 60° increase the performance of the structures considerably. It is also concluded that split-disk tests are efficient to determine the performance of these tubular structures which are usually used under internal pressure developing high hoop stresses.

Hoop Tensile Strength and Fracture Behavior of Continuous Fiber Ceramic Composite (CFCC) Tubes from Ambient to Elevated Temperatures

Presently, continuous-fiber ceramic composites (CFCCs) are considered leading candidate materials for many high-temperature applications, such as high-pressure heat exchangers, radiant burner tubes, and engine combustors. To adequately evaluate these materials in their cylindrical configurations, a hoop tension test is needed.

On the subsequent yielding of an aluminum alloy following cyclic prestraining

Thin-walled tubular samples of 6061 aluminum alloy are cycled in the axial direction between reversed stress limits until a steady-state condition is achieved. Following cyclic loading, the samples are subjected to internal pressure to determine the subsequent hoop tensile yield strength. A small-offset definition of yield is employed to relate the onset of plastic flow to dislocation processes. Samples in the -T651 and -0 tempers are studied, and, it is found that the subsequent yield strength determined in this way may be greater than, less than, or nearly equal to the initial hoop tensile yield strength depending on the interaction of three factors: i) the relationship between the Bauschinger effect and the cross effect under plane, biaxial stress loading, ii) the initial state of the material (i.e., degree of initial anisotropy), and iii) the final state of the material after axial cyclic loading (i.e., dislocation structure and deformation history).