Types of Reinforcing Fibre

The number of above-listed parameters indicates how many different types of reinforcing fibre structures may be used in concrete-like composites. 

Table 63 Average composition and main property examples of the three main types of glass fibres used in polymer reinforcement...

Various types of oxide fibres available commercially can be considered as suitable reinforcements other than the types of fibres listed in Table 3.2 ... 

As a reinforcement, Kevlar 49 is in intense competition with carbon fibre. They are both much more costty than E-glass, and are considered only where their outstanding mechanical properties are really needed. Not surprisingly, there is currently increasing interest in hybrid composites. A combination of two or more types of reinforcement is used to produce an optimum profile of cost and properties for a given application. 

The reinforcement types which will be discussed are glass fibre, carbon fibre and aramid fibre. Each of these is not a single fibre type but more a family of fibres with a range of properties. Typical properties of a range of reinforcement fibres are given in Table 1.2 The strength and strain figures... 

The thermal expansion of the composite depends not only on the type of reinforcement and the type of matrix but also on the geometry of reinforcement, its volume fraction and of course the amount and type of any filler present. Because it is a function of the fibre orientation, the thermal expansion will depend on the direction considered. Thermal expansion coefficients for some E glass composites are shown in Table 1.5. 

These factors dictate the type of reinforcement which can be used. Continuous filament mat and needle mat (both glass fibre) are most common, but woven roving and multi-axial (glass, carbon, etc.) can also be used. 

No significant differences of the thermal expansion behaviour were observed for samples reinforced with the same type of C fibre, but different matrix precursors. Also, at low temperatures, the coefficient of thermal expansion is dominated by the fibres, a at liquid He temperature is nearly zero. The composites, reinforced with different fibre types, possess extremely different expansion behaviour. The coefficient of thermal expansion of the high-modulus... 

Tool design and manufacture is a very expensive business, and before a design is committed to it prototypes will usually be made and tested. They are made by machining from solid material of the same type as that proposed for the injection-moulded product, if available. Some care has to be exercised in results of tests on prototypes made in this way, because orientation of reinforcing fibres, or of polymer molecular chains in machined gears may be inconsistent with those in mouldings. 

The global market for advanced composites consumes over 140,000 tonnes/year of fibre reinforcements (of carbon, aramid, high modulus PE, boron, various types of glass fibres). 

The development of the different types of glass fibre has been in response to demand from specific markets, and the latest call is for improvement in long-term resistance to chemicals. The whole sector termed anti-corrosion is now one of the most important applications for glass fibre-reinforced materials, embracing the industries of marine products, chemicals, pulp and paper, and food manufacture as well as water treatment, anti-pollution, power plant desulphurisation, and many other important sectors dealing with environmental protection. 

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