Glass fibre reinforced polymers casing

As an example of the complexity of organisational issues associated with Life Cycle Engineering, Figure 6.1 shows the possible stakeholders in a recycling scheme of an automotive under-the-bonnet application, in this case a radiator end-cap made from a reinforced polymer, short glass fibre-reinforced polyamide 66 (PA 66 + GF). 

Table 2.7 shows a comparison of the tensile strengths of a range of engineering polymers with and without glass fibre reinforcement. With the exception of epoxy resins the incorporation of 25-50% of glass fibre, leads to a dramatic increase in tensile strength by a factor, in the case of PTFE, of sevenfold. 

FIGURE 9.4 Comparison between the predicted and measured final failure stress for ( 55 ) E-glass/M Y750 laminates subjected to biaxial loads (Test Case No 9-range of biaxial stress ratios). (Reprinted from Failure Criteria in Fibre Reinforced Polymer Composites The World-Wide Failure Exercise, Hinton, M. J., A. S. Kaddour, and P. D. Soden, eds., Elsevier, London, 2004, with permission from Elsevier.)... 

Polymers below the glass transition temperature are usually rather brittle unless modified by fibre reinforcement or by addition of rubbery additives. In some polymers where there is a small degree of crystallisation it appears that the crystallines act as knots and toughen up the mass of material, as in the case of the polycarbonates. Where, however, there are large spherulite structures this effect is more or less offset by high strains set up at the spherulite boundaries and as in the case of P4MP1 the product is rather brittle. 

A study of polystyrene and poly ether sulfone, with and without 20% glass reinforcement [45], found that, after one year s exposure in Saudi Arabia, strength and ductility were retained better in the reinforced polymers, although the values in all cases fell to 50-77% of their original values. Other studies have shown that short glass fibres cause a significant increase in as-moulded residual stress in such polymers as well as in semi-crystalline polymers [46,47]. This can lead to stress cracking in service. 

Nowadays, these polymers (and others) are often reinforced with short-staple glass fibre or in some cases carbon fibre. The principle effects of such reinforcement are (a) to stiffen the material - increased modulus, (b) to increase its tensile strength, (c) to lower its coefficient of linear thermal expansion, (d) to increase its ceiling service temperature, (e) to reduce its impact strength - usually relatively unimportant for gears. Table 4.1 shows these effects (ref. 2). 

Polyimide characterised by thermal and thermal-oxidative stability at elevated temperatures, chemical resistance and good mechanical properties is relatively new in the family of polymer foams [3]. In some cases, depending on the nses, additional reinforcement can be inclnded. Examples are fibre reinforced foams and syntactic foams which are composites containing hollow glass, ceramic or plastic micro-spheres dispersed throughout the polymer matrix. 

Polymer Matrix Composites Where low-specific gravity is important, as in the case of aviation construction, an important role in supplementing and even replacing metals has been played by polymer matrix composites reinforced with continuous ceramic fibres, mostly carbon and glass fibres (—>Figs. 3.12. Tradition... 

The main requirements to the interior parts of a car are attractive appearance combined with good mechanical properties and matching tight tolerances of the part after processing. Thermoplastic styrene-based polymers are often chosen due to the above mentioned aspects. In many cases, neat styrene-based thermoplastics need to be reinforced with glass fibres in order to fulfill these requirements. Depending... 

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