Fibre-reinforced plastic composite types

The creep and fatigue behaviour for natural fibre-reinforced plastics is less weU understood than for glass fibre-reinforced plastics because of the lack of systematic and detailed information. Limited information is currently available oti the effects on the fatigue behaviour of natural fibre-reinforced plastics of different composite parameters such as fibre type, the quality of fibre-matrix adhesion and fibre properties and their content. 

An further alternative approach being developed worldwide is to replace the steel completely by fibre-reinforced plastics (FRP), which consist of continuous fibres as carbon, glass or aramid, set in a suitable resin to form a composite rod or grid. These materials have high tensile strength, low density and are non-magnetic they can be used both for new structures and for repair of existing ones. The mechanical properties of FRP are determined by the amount and type of fibre, while the durability will be a function of both the resin and the fibre. 

The data presented here have been selected with the aid of the RAPRA database on reinforced plastics and composites, from commercial trade literature and sources, from the composites literature and the authors and their colleagues private sources. We have always tried to select information on well-prepared and described systems using modern fibre types and matrices. Inevitably it has not always been possible to do this and in some cases we have had to use older data, information where the fibre or resin is not fully specified or material for other than unidirectional systems. In doing this we have had to balance the need for information with the uncertainties mentioned, but where we have done this we believe that the information quoted, though not ideal, is the best way of filling a real gap. 

Fillers may be divided into particulate and fibrous types. Particulates include calcium carbonate, china clay, talc and barium sulphate. Fillers affect shrinkage on moulding and the dimensional stability of the finished plastic, increase tensile strength and hardness, enhance electrical insulation properties and reduce tackiness. They also impart opacity and colour (Figure 3.16). Carbon black is now the most widely used filler for polymers usually in the form of furnace carbon black, which has a particle diameter of 0.08 mm. Fibrous fillers reinforce polymers and greatly increase their tensile strengths. They include fibres of glass, textile and carbon. Plastics filled with fibrous fillers are known as composites. 

Figure 3.16 Tensile strengths of reinforced Type II electroplated and hot-pressed copper. Broken line as predicted by Law of Mixtures. Source Reprinted with permission from Howlett BW, Minty DC, Old CF, The fabrication and properties of carbon fibre/metal composites, Paper No. 14, International Conference on Carbon Fibres and Applications, The Plastics Institute, London, 1971. Copyright 1971, Maney Publishing (who administers the copyright on behalf of lOM Communication Ltd, a wholly owned subsidiary of the Institute of Materials, Minerals Mininng).

The degree of thermo-plasticity achieved by chemical modification depends on several factors including the type of chemical, the degree of substitution, the method used and chemical composition of the fibre. From the standpoint of reinforcing materials, it is essential that modification only takes place on the matrix of the fibre leaving the cellulose backbone... 

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