Design of CNG tank made of aluminium and reinforced plastic

A compressed natural gas storage tank suitable for gas operated vehicles can be made of thin-walled aluminium liners with a glass/epoxy reinforcement overwind. The hybrid construction allows the higher tensile strength of the glass reinforcement to be utilized, whilst giving a structure which weeps before burst and self-health. The advantages of the chosen construction can only be maximized for the optimal wall thickness and optimal stiffness of the composite shell after optimal prestressing of the tank. The purpose of the design task is to optimize the construction. This paper gives the methodology involved in achieving this using analytical techniques. The reliability of the design method together with the advantages of the chosen structural solution are proved by the manufacture and testing of prototype tanks.     

A novel bogie design made of glass fibre reinforced plastic

This paper presents a completely new design of a bogie-frame made of glass fibre reinforced composites and its performance under various loading conditions predicted by finite element analysis. The bogie consists of two frames, with one placed on top of the other, and two axle ties connecting the axles. Each frame consists of two side arms and a transom between. The top frame is thinner and more compliant and has a higher curvature compared with the bottom frame. Variable vertical stiffness can be achieved before and after the contact between the two frames at the central section of the bogie to cope with different load levels. Finite element analysis played a very important role in the design of this structure. Stiffness and stress levels of the full scale bogie presented in this paper under various loading conditions have been predicted by using Marc provided by MSC Software. In order to verify the finite element analysis (FEA) models, a fifth scale prototype of the bogie has been made and tested under quasi-static loading conditions. Results of testing on the fifth scale bogie have been used to fine tune details like contact and friction in the fifth scale FEA models. These conditions were then applied to the full scale models. Finite element analysis results show that the stress levels in all directions are low compared with material strengths.     

Failure analysis of a leaching reactor made of glass-fiber reinforced plastic

This paper reports a failure analysis of a leaching reactor in a zinc plant that suffered from a catastrophic failure after less than two years of operation. During normal operation the bottom of the reactor fell out suddenly, releasing the contents, a high-temperature acidic solution, into the surroundings in an uncontrollable manner. The reactor was made of glass-fiber reinforced plastic. Microscopy, thermal analysis, mechanical testing and finite element analyses were employed to investigate the causes of the failure. There were several contributing factors but the root cause was poor adhesion between the bottom and the joint laminate, which was caused by insufficient grinding during the surface preparation stage of the joint.     

纤维复合材料在低温容器内支撑结构中的应用

介绍低温容器中应用的纤维复合材料内支撑结构的形式,并对常用纤维复合材料的性能在常温和低温间的变化进行比较,实验数据可作为设计低温容器内支撑结构的依据.纤维复合材料作为低温容器支撑材料具有良好的综合性能,其性能机理和影响因素的有待进一步研究.     

Numerical analysis of a sling support arrangement for GRP composite pressure vessels

A flexible sling support arrangement for horizontal glass reinforced plastic pressure vessels is examined using advanced finite element methods. A mathematical model is produced employing a suitable analysis capable of representing the non-linear behaviour of a sling supported GRP vessel. This system is used to examine the phenomena occurring at the interface between the vessel and the supporting belt. Each component is initially considered some distance apart and then brought together using three-dimensional contact surfaces. External loads are thereafter applied to the combined model. Although several numerical difficulties arise due to the difference in flexibility between the vessel shell and the sling support, these are overcome and the resulting vessel strains and contact interface pressures show good agreement with experimental work. The magnitudes of the strains at the location of the saddle horn are significantly reduced. Results of a parameter study are also presented which show the effect of the sling position together with the influence of the wrap-round angle and a number of recommendations are made with respect to design.     

Fracture mechanics of multilayer and reinforced spherical type pressure vessels at reduced test temperature

The results of experimental investigations of the strength of spherical metal shells under internal hydrostatic loading are analyzed. The characteristic features of fracture of a spherical pressure vessel at a test temperature of 210–215 K are revealed.Translated from Problemy Prochnosti, No. 1, pp. 29–33, January, 1989.     

The compression strength of unidirectional carbon fibre reinforced plastic

A simple compression test, suitable for quality control measurements on unidirectional carbon fibre composite, is described. The specimen, a plane bar, with aluminium end tabs attached, is compressed by applying shear forces over the ends. With either type 1 or type 2 treated fibre the failure mode is one of shear over a plane at approximately 45° to the fibre axis. With untreated type 1 material failure is due to delamination. The variation of the compression strength of treated material with fibre volume loading is linear, the values being considerably below those predicted by buckling theory. Increasing void content causes a steady decrease in compression strength, and off-axis strength values are above those given by the maximum work criterion. The present work supports the recently proposed view that the compression strength of unidirectional carbon fibre composites at room temperature is not governed by fibre buckling but is related to the ultimate strength of the fibre.     

The crush behavior of glass fiber reinforced plastic sections

The crush response of glass fiber reinforced plastic tubes, of cylindrical, square and rectangular section, made from unidirectional tape with various alternating 0° and 90° lay-ups, and also of small samples cut from these tubes, was studied with particular reference to the effects of the geometry of the crush trigger initiator. It was found that the propagation of delamination cracks contributed little to the energy absorption capacity, most of the crush resistance being derived from the development of kink bands in the fiber structure. The crush resistance of square tubes with thinner walls was largely provided by the corners. As the wall thickness increased, the planar portions contributed more to the crush resistance. Approximate estimates of the specific energy may be made from crush tests of simple flat sections. The trigger geometry alters the energy absorption capacity by the extent to which it generates deformation flaws which can then propagate within the wall structure.Softer crush anvils reduce the effectiveness of the trigger crush initiator and can lead to global failure of the section, rather than to stable, progressive crush.     

On the optimum design of reinforced slabs

Summary A problem of optimum design of reinforced slabs is analyzed assuming a rigid, perfectly-plastic model of both concrete and reinforcement. For a slab of constant thickness such static field is sought which minimizes the total amount of reinforcement under constant limit load; for a slab of varying thickness, the total cost of materials is assumed as a design criterion. Two approximations of the nonlinear cost function are introduced and the corresponding static and kinematic relations are discussed in detail. Several examples of circular and annular slabs under symmetric and non-symmetric loading are considered in order to illustrate the theory.

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Zusammenfassung Unter der Annahme eines starr-plastischen Modells von Beton und Armierung wird ein Problem der optimalen Auslegung armierter Platten untersucht. Für eine Platte konstanter Dicke wird ein statisch mögliches Beanspruchungsfeld gesucht, welches den gesamten Armierungsaufwand bei konstanter Traglast zu einem Minimum macht; für eine Platte veränderlicher Dicke werden die gesamten Materialkosten als Entwurfkriterium angenommen. Es werden zwei Näherungen der nichtlinearen Kostenfunktionen eingeführt und entsprechende statische und kinematische Beziehungen im einzelnen diskutiert. Etliche Beispiele kreis- und ringförmiger Platten unter symmetrischer und nichtsymmetrischer Belastung werden zur Illustration der Theorie betrachtet.

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The influence of through thickness properties on glass reinforced plastic laminated structures

Glass reinforced plastic (GRP) laminate made from layers of glass fibre in the form of chopped strand mat and polyester resin and constructed by the hand lay-up procedure is extensively used for pipes and vessels in the chemical process and other industries. In design for strength, consideration in general is given only to normal stresses or strains in the plane of the laminate. In operation, certain stress systems arising in pipes and pipe components suggest that through-thickness properties of the laminate need to be considered. Compression, tension, bending, torsion and hydrostatic pressure tests were carried out on a 229 mm thick laminate constructed in the laboratory. Elastic moduli as well as fracture stresses were derived, including those for through-thickness tension and interlaminar shear. Limited tests on thinner laminates are also reported.Implications of the results for the design of smooth GRP pipe bends are discussed.     

Viscoelastic behaviour of a unidirectional fibre reinforced plastic

The orthogonal linear viscoelastic constitutive equation is given by the Laplace transform domain elastic constants which are calculated from the law of mixture and a structural unit cell. Non-linear constitutive relations in high stress regions are derived by considering non-linear properties of the components and the stress redistribution in the matrix on account of debonding between fibre and matrix. A linear failure criterion and a fracture criterion are also investigated theoretically. Experimental works are conducted for uniaxial and biaxial specimens of cold-drawn copper fibre-epoxy resin composite having various fibre volume fractions and fibre directions. Fairly good agreements are observed between the calculated and experimental results.     

Characterization of unidirectional carbon fibre reinforced plastic laminates

The purpose of the present paper is to outline a set of recommended tests in order to characterize the behavior of carbon fibre reinforced plastic laminates. The tests outlined in this contribution are classification of visual defects, dimension and density, fibre and resin content, tensible strength, apparent interlaminar shear strength, in-plane shear modulus, dynamic torsion property, static bending property, dynamic bending property, and thermal expansion coefficient. As a selected example, results of two tensile tests on CFRP laminates are reported.     

Creep behaviour of glass reinforced plastic box beams

Three 6m long box beams were made from glass-reinforced plastic material and subjected to various loading procedures to study their creep behaviour. The first beam carried a constant load, equivalent to one-third its ultimate load, the second was alternately loaded and unloaded, with a similar load, for various time intervals and the third was left to support its own weight. Measurements were taken at specified time intervals over a period of about 20 months. It was found that glass-reinforced plastic material is more liable to creep than other conventional construction materials. Initial deflections increase by over 100% over the whole time period, but most of this occurs in the first 1000 hours. A set of best fit equations were found which can be used to predict the creep behaviour.     

Micro-mechanical analysis of splitting failure in concrete reinforced with fiber reinforced plastic rods

The present investigation provides a micro-mechanical model for the splitting failure analysis of fiber reinforced plastic (FRP) reinforced concrete members subjected to longitudinal tensile stresses. The model consists of three co-axial cylinders: (a) the inner elastic FRP rod; (b) the mid cracked part of concrete; and (c) the outer elastic part of concrete. The anisotropic properties of reinforcement, the compatibility of longitudinal strain at interface and the effect of Poisson's ratio of concrete are taken into account in the analysis. The method can be used to predict the stress distributions in the hybrid structure and the relations between the growth of cracks and the applied end forces. It is found that the number of splitting cracks and the material properties of the anisotropic FRP rods are not the dominant factors in splitting failure. It is also observed that neglecting Poisson's ratio of cracked concrete may under-estimate stresses in the hybrid structure.     

Experimental composites made of electron beam irradiated reinforced fillers

This study investigated the influence of electron beam irradiated reinforced fillers on the three body wear and flexural strength of experimental composite blends. Three formulations of reinforced fillers were investigated: (A) high loaded inorganic filler composite with 60 wt.% SiO₂, (B) low loaded inorganic filler composite with 40 wt.% SiO₂, (C) organic filler composite (precipitated Bis-phenol-A-di-methacrylate). The fillers were assigned to two subgroups of unswollen (A, B, C) and monomer swollen (A_s, B_s, C_s) fillers. The experimental blends (matrix: Urethane-dimethacrylate) were mixed using un-treated, annealed (90 °C), or electron beam irradiated fillers with 30 and 90 kGy, respectively. All specimens were heat-cured for 20 min at 140 °C. Three-body abrasion and flexural strength tests were performed. The highest flexural strength was evaluated for composites made of the 30 kGy irradiated type B_s filler. The comparison with annealed fillers showed that the effect was independent of increasing temperatures during the radiation process. Blends with a SiO₂ content of 60 wt.% (type A, A_s) had significantly less wear than blends with 40 wt.% (type B, B_s) or blends with organic fillers (type C, C_s). The flexural strength of the composite could be improved by using pre-irradiated reinforced fillers. However, wear was not affected using this procedure.     

The effects of vertical and horizontal placement on no-vent fill of cryogenic insulated vessels

Since cryogenic vessels and products are widely applied into industries, scientific explorations and daily lives, more and more investigations on no-vent fill technologies have been conducted to protect resources and environment. In this paper, liquid-vapor interface area or liquid volume as a function of liquid height was calculated by the use of integration method. Based on the analysis of the effects of the liquid-vapor interface area on vapor condensation, the rising liquid-vapor interface area was considered as an important influencing factor which was seriously studied in the form of interface area ratio . Experimental results indicated that the horizontal tanks performed better in no-vent fills than the vertical ones given the same operational condition. For the reason that the effects of initial condition and transfer properties on no-vent fills were excluded, the increasing rising liquid-vapor interface area was concluded as a main explanation to support that horizontal placement was more feasible in no-vent fills.