Fatigue Behaviour of Reinforced Plastics

The general fatigue behaviour which is observed in glass fibre reinforced plastics is illustrated in Fig. 3.32. In most grp materials, debonding occurs 

There is no general rule as to whether or not glass reinforcement enhances the fatigue behaviour of the base material. In some cases the matrix exhibits longer fatigue endurances than the reinforced material whereas in other cases the converse is true. In most cases the fatigue endurance of grp is reduced by the presence of moisture. 

Fracture mechanics techniques, of the type described in Section 2.21.6 have been used very successfully for fibre reinforced plastics. Typical values of K 

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Jones CJ et al. Environmental fatigue of reinforced plastics. Composites, 14, 288-293, 1983. Jones CJ et al. Environmental fatigue behaviour of reinforced plastics, Proc Royal Society of London, 396, 315-318, 1984. 

Jones, C.J. et al. (1984) Environment fatigue behaviour of reinforced plastics. Proc. Royal Society of London 396, 315—38. 

Harris B et al, Fatigue behaviour of carbon fibre reinforced plastics. Composites, 21(3), 232-242, 1990. 

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. 

In this book no prior knowledge of plastics is assumed. Chapter 1 provides a brief introduction to the structure of plastics and it provides an insight to the way in which their unique structure affects their performance. There is a resume of the main types of plastics which are available. Chapter 2 deals with the mechanical properties of unreinforced and reinforced plastics under the general heading of deformation. The time dependent behaviour of the materials is introduced and simple design procedures are illustrated. Chapter 3 continues the discussion on properties but concentrates on fracture as caused by creep, fatigue and impact. The concepts of fracture mechanics are also introduced for reinforced and unreinforced plastics. 

Although, in general, the use of fibre-reinforced plastic composites is continually increasing, certain aspects of their behaviour are still poorly understood. An example is their viscoelastic, viscoplastic or time-dependent behaviour due to creep and fatigue loadings (Fig. 23.7). 

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