Corrosion of glass fibres

Cellular corrosion of glass fibre reinforced concrete building elements is of concern in that it has a severe effect on the tensile strength of such elements. 

Corrosion of glass fibres in neutral aqueous solutions... 

Sheard PA, Jones FR (1986) The stress corrosion of glass fibres andepoxy composites in aqueous environments. In Loo TT, Sun CT (eds) Proceedings of the international symposium on composite materials and structures, Beijing, 10-13 June 1986, pp 118-123 Suh D, Ku M, Nam J, Kim B, Yoon S (2001) Equilibrium water uptake of epoxy/carbon fiber composites in hygrothmnal environmental conditions. J Compos Mater 35(3) 264-278 Tucker WC, Brown R, Russell L (1990) Corrosion between a graphite lymta- cmnposite and metals. J Compos Mater 24(1) 92-102... 

Environmental stress corrosion cracking (ESCC) of glass fibres... 

ECR and boron-free glass fibres have improved durability over E glass so that ESCC of glass fibre composites is less likely when modem glasses are employed. The design of glass fibre composites for resistance to stress corrosion cracking has been discussed in detail elsewhere [7,8]. 

Environmental stress corrosion cracking of glass fibre composites [33 2]... 

The stress corrosion, that is the corrosion as a result of the combined action of chemical and mechanical action, of glass fibre reinforced plastics in aqueous media has been reviewed by Roberts [73], Hogg and Hull [74] and Menges and Lutterbeck [75], although none of the work referenced is specific to sea water exposure. The subject of the corrosion of FRP under static loading is discussed in some detail in Chapter 3, and cyclic loading or fatigue is the subject of Chapters 5 and 11 in this book, but both these topics will be briefly mentioned here in the context of marine applications. 

The tensile strength of glass fibres reduces at elevated temperatures but can be considered constant for the range of temperatures at which polymer matrices are exposed. The tensile strength also reduces with chemical corrosion and with time under sustained loading. 

E glass is highly resistant to most chemicals but it is attacked by both mild acids and mild alkalis. The extensive use of glass fibre reinforcement in chemical plants is reliant upon the corrosion resistance of the polymer matrix and its ability to ensure that the glass fibres do not become exposed to the environment (see 1.3.14, stress corrosion). 

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. 

The fibre surface has a considerable influence on the composition of the transition zone. For highly corrosion resistant glass fibres with specially coated surface, like CemFILl, this zone is very porous. This is in contrast to the strong interface formed around steel and asbestos fibres. In various composites with different kinds of fibres and matrices, the transition zone is formed as a result of chemical affinity, quality of the fibre surface and the penetration of the cement paste into the bundles of fibres. Furthermore, the ITZ may be different above and below a fibre due to bleeding and water lenses below fibres. Higher porosity of the ITZ around steel galvanized reinforcements than around ordinary steel rebars was observed by Belaid et al. (2001). 

A whole range of these resins is available. They are produced by the reaction of polyhydric alcohols and poly basic acids. An important use of these resins is in the manufacture of glass fibre reinforced polyester laminates which, in addition to their great strength, have a high heat and corrosion resistance. 

Figure 8.3 The surface of glass fibres removed from aged composites (after Bentur [I I]) (a) E glass removed from a composite after ageing for 2 months in water at 20°C, showing severe corrosion (b) AR glass (CemFIL-l) removed from a composite after ageing in water at 20°C for 1/2 year, showing only mild damage.

Plastics also find increasing use in vehicles for both water and air transport. Glass-fibre-reinforced plastic boats are widely used as a result of their economy in manufacture, ease of maintenance, lightness of weight and, for military purposes, antimagnetic characteristics. The non-corrosive nature of plastics also leads to their widespread use in boat fixtures and fittings. In aircraft, plastics are particularly useful on account of their low density. 

Technical advantage/function Basalt rock wool is used for noise insulation in automotive exhaust units for the purposes of noise absorption. Vital technical requirements are temperature resistance, noise absorption behaviour, corrosion resistance and mechanical stability. Now textile continuous glass fibres and biosoluble mineral wools are also used for this application in exhaust units. 

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