Bending of glass fibre-reinforced plastic (GFRP) plates on elastic supports

This study is concerned with the mechanical properties of a fibreglass reinforced polyester resin of laminar construction with consideration given to the application of the results to the analysis, in bending, of a plate of similar material. Tension and compression tests were performed to obtain the stress-strain relationship and ultimate stresses and strains. Because of the inherent scatter of results due to the nature of the material, average values, along with maximum and minimum limits, are determined. Flexural tests were conducted and moment-curvature relationships were obtained both theoretically and experimentally. Creep tests showed that, for loads well below the failure load, creep effects are almost negligible when the fibres are oriented to the longitudinal axis of the specimen. As the results in bending are not as scattered as those for tension and compression, this leads one to believe that they might be more appropriate for use in plate theory.

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Résumé On étudie les propriétés mécaniques d’une rśine polyester renforcée de fibres de verre et de structures laminaires, en ayant en vue l’application des résultats à l’étude en flexion d’une plaque d’un matériau similaire. Les essais de traction et de compression ont été réalisés afin d’obtenir la relation contrainte/déformation ainsi que les contrainteses et déformations ultimes. La nature du matériau déterminant une dispersion des résultats, on a fixé des valeurs moyennes comportant des limites maximales et minimales. On a réalisé des essais de flexion tant théoriques qu’expérimentaux, et obtenu des relations moment-courbure. Les essais de fluage montrent que pour des charges nettement au-dessous de la charge de rupture les effets du fluage sont presque négligeables si les fibres sont disposées longitudinalement dans l’éprouvette. Comme les résultats en flexion sont moins dispersés que ceux obtenus en traction et en compression, on peut supposer qu’ils se prêtent mieux à être utilisés dans la théorie des plaques.

     

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.     

High-speed grinding of isophthalic resin glass fibre reinforced plastic pipes

Abstract

In an experimental investigation some of the parameters affecting the efficiency of cylindrically grinding glass fibre reinforced plastic pipe section have been examined. For a range of grinding conditions, 70% glass isophthalic resin workpieces were ground, using a variety of aluminium oxide and silicon carbide grinding wheels. Such parameters as grinding forces, specific energy, and wheel wear are collated. Also examined was the effect on the grinding parameters and workpieces when the infeed rate is increased, for grinding both with and without coolant.

MST/383     

A study on estimation of damage accumulation of glass fibre reinforce plastic (GFRP) composites under a block loading situation

Many cumulative damage theories have been used in lifetime calculation of GFRP composite components. However, it is well known that linear damage accumulation models are inadequate for predicting the cumulative damage in GFRP compositeas due to their dominant viscoelastic characteristics. This paper discusses the outcomes of application of damage accumulation models proposed by Palmgren-Miner [Miner MA. Cumulative damage in Fatigue. J Appl Mech 1945;12(September):A159–64], Broutman and Sahu [Broutman LJ, Sahu SA. New theory to predict cumulative fatigue damage. In: Fiberglass reinforced plastics, composite materials: testing and design (second conference), ASTM STP 497; 1972. p. 170–88], Hashin and Rotem [Hashin Z, Rotem A. A cumulative damage theory of fatigue failure. J Mater Sci Eng 1978;(34):147–60] and Epaarachchi and Clausen [Epaarachchi Jayantha A, Clausen Philip D. On predicting the cumulative fatigue damage in glass fibre reinforced plastic (GFRP) composites under step/discrete loading. Composites Part A: Appl Sci Manuf 2005;36(9):1236–45], to calculate the lifetime of GFRP composite samples under repeated block loading situations.     

Evaluation of cumulative damage in glass fibre reinforced plastic by ultrasonic method

This paper presents the cumulative damage in glass fibre reinforced plastic composite during loading and unloading at regular intervals using the continuous monitoring of ultrasonic test instrument. The result shows that the ultrasonic attenuation increases with an increase in the tensile load, which provides the change in internal damage of composites.     

Local bond stress-slip relationships of glass fibre reinforced plastic bars embedded in concrete

The bond relationships between glass fibre reinforced plastic bars with polyester matrix and concrete is investigated in order to obtain information concerning the possible use of these bars for the reinforcement of concrete constructions, where the use of ordinary steel bars could have certain disadvantages due to the possibility of corrosion. The results obtained are used to develop a model of the stress-slip relationship and to estimate the anchorage lengths needed to embed these bars in concrete casts.

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Resume On a effectué une recherche sur la relation d'adhérence entre des barres de résine polyester renforcée de fibres de verre (GRP) et le béton, dans le but d'obtenir des informations sur l'emploi éventuel de telles barres comme armatures pour les ouvrages en béton armé, dans lesquels l'emploi de barres ordinaires en acier présente plusieurs inconvénients, dont ceux liés au phénomène de la corrosion. Les résultats obtenus ont permis d'établir un modèle de la relation contrainte d'adhérence-glissement, et de formuler une estimation des longueurs nécéssaires pour l'ancrage de telles barres dans des coulée de béton.

     

Polymer-modified glass fibre reinforced gypsum

Glass fibre reinforced gypsum, modified by addition of specially selected and developed thermosetting polymers, is the basis of a new composite material, called PGRG. An investigation has been performed into its mechanical properties such as bending strength, tensile strength and long-term performance under constant load and fatigue load. The influence of moisture and temperature on mechanical properties has been determined. The equilibrium moisture content at various relative humidities, the moisture content under natural weathering conditions, the coefficient of linear expansion and the microstructure have been studied. Furthermore, the durability has been investigated under accelerated ageing conditions and outdoor exposure. The results have shown that the polymer-modified glass fibre reinforced gypsum has good mechanical properties under tension and, unlike unmodified gypsum, is resistant to the Western European climate. A variety of new outdoor applications for gypsum are likely to be possible now: The material has already been used successfully for outdoor applications in the UK, the Middle East and The Netherlands.

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Resume Le platre renforcé de fibres de verre, modifié par l'addition de polymère thermodurcissable spécialement sélectionné et fabriqué, forme la base d'un nouveau matériau composite appelé PGRG, dont on a examiné certaines propriétés mécaniques: résistance à la flexion, à la traction et performance à long terme sous charge constante et charge de fatigue. On a déterminé l'influence de l'humidité et de la température sur les propriétés mécaniques. On a également étudié l'équilibre de la teneur en eau à différentes humidités relatives, la teneur en eau en exposition naturelle, le coefficient d'expansion linéaire et la microstructure. On a aussi examiné la durabilité dans des conditions de vieillissement accéléré et l'exposition à l'atmosphère. Les résultats ont montré que les propriétés mécaniques du composite sont bonnes et que, à la différence du platre non traité, il peut résister au climat d'Europe Occidentale. Ceci permet d'envisager maintenant pour le platre diverses applications en ouvrages extérieurs. Le matériau a déjà été utilisé avec succès pour ce type d'applications en Grande-Bretagne, aux Pays-Bas et au Moyen-Orient.

     

Rheological characterisation of discrete long glass fibre (LGF) reinforced thermoplastics

Three experimental techniques have been employed to assess the rheological behaviour of discrete long glass fibre reinforced polypropylene and propylene/ethylene copolymers. A Carri Med cone and plate rheogoniometer has been used to determine shear viscosity as a function of strain rate and time at temperatures relevant to the extrusion and injection moulding processes. A bubble inflation test (BIT) has been designed and used to characterise the behaviour of these composites under the extensional flow fields typical of blow moulding and thermoforming. Finally a squeeze load test (SLT), similar to those developed for sheet moulding compounds (SMC) and glass mat thermoplastics (GMT), has been used to explore the rheological behaviour of the long glass fibre (LGF) materials under compression moulding conditions, in particular to assess the relative importance of shear and extensional flow.     

Carbon fibre and glass fibre hybrid reinforced plastics

A review of the literature on carbon fibre and glass fibre hybrid reinforced plastics is presented. There are indications that the incorporation of both fibres into a single matrix sometimes leads to better properties than would be expected from consideration of the rule of mixtures. The incorporation of glass fibres in cfrp appears to improve impact properties and to increase the strain to failure of the carbon fibre in tension. The addition of carbon fibres to the surface of grp beams markedly increases the flexural modulus. A system of nomenclature for the diverse types of hybrid composite lay up is proposed.     

Fretting of glass fibre reinforced composites

Favourable specific mechanical properties of polymer matrix composites make them an attractive material for application in many engineering structures for which they offer substantial improvements over metals. The paper deals with fretting behaviour of unidirectional glass epoxy composites/metal contacts. Fretting is a plague for many industries: failures, loss of matter, loss of function can be induced by fretting. It occurs in all quasi-static contacts and appears as a complex wear phenomenon where a lot of parameters have been studied. From the interface tribology concept, the velocity accommodation mechanisms are discussed for different fibre orientations versus the contact surface of the glass fibre reinforced epoxy material. Results were analysed in two steps. From friction logs, Running Conditions Fretting Maps (RCFM) were first plotted in order to give an analysis of contact conditions and determine the associated material responses. The tribological degradations were then analysed. Differences between the different fibre orientations are mainly discussed on the basis of the stiffness of the anisotropic material and the velocity accommodation in the contact.     

Study of variation of thermal diffusivity of advanced composite materials of E-glass fibre reinforced plastic (GFRP) in temperature range 5–300 K

Modified Angstrom method is applied to study the variation of thermal diffusivity of plain woven fabric composite in closed cycle cryo-refrigerator (CCR) based set up in the temperature range 5–300 K. The set up used is plug in type and its small size offers portability. The set up works without use of any liquid cryogen. The temperature versus thermal diffusivity curve shows three distinct regions viz. 5–30 K, 30–120 K and 120–300 K. In the first region thermal diffusivity varies exponentially and rapidly. In the second region thermal diffusivity changes exponentially but relatively slowly than that in the first region. In the last region the change in thermal diffusivity with temperature is exponential in nature but very slow.     

Effects of static–fatigue (tension) on the tension–tension fatigue life of glass fibre reinforced plastic composites

The effects of static–fatigue interaction on tension–tension fatigue life of glass fibre reinforced plastic (GFRP) composites were investigated. This paper proposed a new static–fatigue model, which is capable of predicting residual strength after a period of static loading. Also an algorithm is proposed to calculate fatigue lives with the inclusion of static–fatigue interaction. Predictions from the proposed static–fatigue model show a good agreement with the experimental results. Static–fatigue interaction has shown a considerable effect on fatigue lives of GFRP composites at intermediate and lower applied stress levels possibly due to a longer exposure to applied loads. At higher load levels approximately greater than 65% of ultimate stress, and higher stress ratios range like 0.5 < R < 0.9, fatigue lives shown to be closer to material’s static–fatigue limits which is shorter than the expected lifetime by cyclic fatigue.     

碳纤维表面嫁接马来酸对碳纤维复合材料力学性能的影响

通过自由基反应在碳纤维的表面嫁接马来酸,通过红外光谱、SEM可以看出马来酸嫁接到碳纤维的表面,嫁接之后的碳纤维与未经表面处理的碳纤维相比,力学性能有了明显的提高,使碳纤维复合材料的层间剪切强度(ILSS)从113MPa增加到127MPa.增加了12.40%,这是因为嫁接之后的碳纤维与未经处理的碳纤维相比,一方面提高了碳纤维的粗糙度,另一方面在碳纤维与环氧树脂之间形成的化学键、分子间作用力、氢键等提高了碳纤维与聚合物基体之间的粘结力,这样通过物理咬合和化学键的共同作用,提高了碳纤维与聚合物基体之间的粘结力.