Fibres, secondary reinforcement

Components in which fibres are added primarily to control cracking induced by humidity or temperature variations, as in slabs and pavements. In these applications, fibres are often referred to as secondary reinforcement In this case the fibres provide post-cracking ductility, but the stresses are smaller than the first crack stress, that is a strain softening material (Figure 1.1). This type of composite is referred to as conventional FRC. 

In fibre reinforced concretes, the fibre volume is much lower (<2% by volume) and the fibres act as secondary reinforcement, mainly for the purpose of crack control. The production of such reinforced concretes is carried out by conventional means. Higher contents of fibres can be incorporated by relatively simple mixing technologies, but using advanced matrix formulations which are based on sophisticated control of the rheology and microstructure of the mix. Such formulations combine dispersants and fillers (e.g. DSP, RPC and DUCTAL [4-6]). The dense microstructure in these composites, as well as their improved rheology can enable the incorporation and uniform dispersion of 2-6% by volume of short fibres, which can provide effective reinforcement. 

Jones, F.R., Interfacial aspects of glass fibre reinforced plastics. In Jones, F.R. (Ed.), Interfacial Phenomena in Composite Materials. Butterworths, London, 1989, pp. 25-32. Chaudhury, M.K., Gentle, T.M. and Plueddemann, E., Adhesion mechanism of poly(vinyl chloride) to silane primed metal surfaces. J. Adhes. Sci. Technol, 1(1), 29-38 (1987). Gellman, A.J., Naasz, B.M., Schmidt, R.G., Chaudhury, M.K, and Gentle, T.M., Secondary neutral mass spectrometry studies of germanium-silane coupling agent-polymer interphases. J. Adhes. Sci. Technol., 4(7), 597-601 (1990). 

Banthia and Nandakumar (2003) have employed secondary polypropylene micro-fibres to enhance the deformation of steel fibre-reinforced concrete. More recently, Dawood and Ramli (2012) proposed the combination of steel fibres with synthetic and palm fibres as a means of reducing the corrosion problems of fibres and improving the flowing and mechanical properties of concrete. Lee et al. (2012) have shown that the blending of nylon and polypropylene fibres improves the spalling protection of FRC subjected to fire. Azhari and Banthia (2012) have blended carbon fibres and nanotubes in the development of smart stmcture materials, such as strain sensors. 

The behaviour of plain and fibre-reinforced concrete elements under tension is considerably affected by the testing technique and it is difficult to eliminate all secondary effects. The specimen configuration and local stress concentrations, the type of gripping system and testing machine stiffness are among the most important factors. To avoid all secondary effects or to reduce their importance and to obtain reliable results, the tests should be... 

This paper should not end without giving some information on present and future applications of this anisotropic polymer carbon. In space technology, carbon fibre reinforced composites are the unique structural material. In aircraft industry all military planes make use of this revolutionary material. Fig. 26 shows the model of a future fighter which combines wings and stabilizers in one structural element. The whole structure consists of advanced composites. Only small parts, i.e. the engines are still made from metals. In today s commercial aircrafts only secondary and tertiary parts are made from CFRP, as shown in fig. 27. There is... 

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