Reinforcement with fibres

Creep behaviour is good even when the temperature rises. Neat polysulfones have medium moduli that involve medium strains for moderate loading. Consequently, creep moduli are also in a medium range at room temperature but they decrease more slowly than the majority of other thermoplastics when the temperature rises. Reinforcement with fibres leads to high moduli and consequently high creep moduli. 

LFRT (long fibre reinforced thermoplastics) are reinforced with fibres about 2 cm long, far from the length of continuous fibres. Practically all the properties are influenced by the addition of fibres. The most significant parameters are ... 

Grades reinforced with fibres 10 mm long can be processed on conventional injection moulding equipment by simply adapting the processes to preserve the fibres. 

Grades reinforced with fibres 20 mm and more in length cannot be processed on conventional equipment. It is necessary to use, for example, the extrusion-compression technique. The process differs too much from conventional injection used for short glass fibre reinforced thermoplastics to measure the influence of fibre length alone. 

As already stated, there are many different methods of processing plastics, according to the material used and the desired finished product. Plastics are wonderful materials for shaping. They can be made into flat sheets, or they can be reinforced with fibres. They can be blow moulded and made into hollow objects such as drinks bottles, or they can be thermoformed for making food cartons. There is a variety of processes for the different synthetic plastics, but all of them start with the required chemicals in pellet, powder or liquid form. These are melted, mixed with additives, heated and shaped. 

Polyester polymers are materials which exhibit various chemistries but all contain ester linkages in the polymer chain. They have attained industrial importance as moulded materials, fibres, packaging film and as structural materials which are reinforced with fibres and fillers. Chemists, John Rex Whinfield and James Tennant Dickson, employees of the Calico Printer s Association of Manchester, patented polyethylene terephthalate in 1941, after advancing the early research of Wallace Carothers. Poly (ethylene terephthalate) is the basis of polyester fibres and fizzy drinks botdes. The first polyester fibre known as Terylene was also developed in 1941. 

Unreinforced thermoplastics are ideal for mass production processing technology and together they constitute the great majority of plastics usage worldwide, although more than half of the output consists of commodity plastics, not intended for durable products. Although thermoplastics can be reinforced with fibres, they have until very recently not been well repre-... 

Hollaway, L.C. and Thome, A. (1987), High technology thermoplastic polymers reinforced with fibres for space appUcations MOD (PE) Contract No. A57A/1733, Final Report, for the Space Department RAE Famborough, Hampshire. 

Hollaway, L.C., Thome, A. and Rankin, I. (1990), High Technology Thermoplastic Polymers reinforced with fibres for space stractures application . Final Contract Report, Contract No. 4064/107/RAE/XR(F) BNSC, November, 1990. 

Fibre-reinforced polymer (FRP) composites are among the increasingly used composites in the industry. FRPs are composite materials made of a polymer matrix reinforced with fibres. The polymer matrix is either a thermosetting or a thermoplastic resin while the fibres are usually fibreglass. 

Saadatmanesh, H., Ehsani, M.R., Li, M.W., 1994. Strength and ductility of concrete columns externally reinforced with fibre composite straps. ACI Structural Journal, 91(4), pp. 434- 7. 

Voigt, T, Bui, K.B., Shah, S.P., 2004. Drying shrinkage of concrete reinforced with fibres and welded-wire fabric. ACI Materials Journal, 2(101), pp. 233-241. 

The fracture activation energy is mainly determined by the substrate nature. Taking as typical example a composite material, reinforced with fibres, for which it is accepted that the fracture energies coincide with those of matrix fracture, the curves presented in Figure 3.424 are typical ones. 

In the case of the composites based on high toughness matrix, e.g. PEEK, the reinforcement with fibres, in the best case will not negatively affect the composite properties. In the case of a weak bond fibre/matrix, for instance PTFE/very short glass fibres, a decrease of fracture toughness is expected. For the rigid matrix (PET at -60 °C), the fibres presence enhances the composite toughness as compared to the ductile matrix. 

The term plastics covers a broader variety of species than the term metals . Hence, without effective classification, the possibilities for oversimplification and confusion are endless. In terms of mechanical performance in automotive applications, and in particular the response to stress, probably the most important distinction is between unfilled plastics and composites. In automotive plastics terms, composite means plastics reinforced with fibres, usually glass. Nowadays there is a very extensive range of distinct materials answering to this description their significance is discussed later. 

It has been shown on elements reinforced with fibres and subjected to bending how the role of the fibres is decisive for crack control. 

Aramid fibre mesh was also used as reinforcement of thin mortar sheets and subjected to impact by projectiles (Kyung and Meyer 2007). The problem of various body-armour products is of considerable importance because of the increased number and intensity of natural disasters, and more importantly, terrorist attacks. The results have shown that brittle matrix composite materials reinforced with fibres and composed of several thin layers have considerable capacity of energy absorption. There are ready-to-use design methods for such structures and already a vast amount of knowledge has been accumulated in this field. 

Reinforcement with fibres may have different results with regard to permeability. Obviously, the control of cracking is better and transport through a system of cracks and microcracks may be reduced. In contrast, the introduction of fibres to the fresh mix usually increases its porosity. 

Both main methods of shotcreting - dry and wet - are used in repair works with additional modifications. Dry shotcrete is based on mixing components with water in the nozzle. It results in high rebound and heavy dusting, which is detrimental for workers health, particularly in closed spaces. Wet shotcrete is mixed with water before projecting. If used overhead, it requires a high amount of set accelerator, which in turn decreases the strength. A mortar modified with polymers and SF and reinforced with fibres is often applied... 

Polyesters are very w idely used because of their wide property range and ease of handling and processing. Shrinkage on moulding can be a problem and reinforcing with fibres (and/or fillers) will reduce the shrinkage values of the cast resins appreciably. 

Unsaturated Polyester Resins Reinforced with Fibres... 

Previous papers on the optimization of composite materials reinforced with fibres concern mostly the high strength composites [1],[2],[3]. Paper [4] deals with op>timization of the internal structure of different kind of a material composed of brittle matrix and ductile fibres. In [A] the optimum fibre orientation is determined using maximum fracture energy as a criterion. The present paper concerns the optimization of a composite element in which brittle matrix is reinforced with ductile fibres, but at another optimization criterion the optimal directions of fibre systems are determined from the minimum strain energy of the element. 

Seven concrete elements numbered from 0 to 6 and seven reinforced concrete elements numbered from 7 to 13 were tested (Fig. 1). The elements 0 and 13 did not contain fibres and those numbers 1 and 7 were reinforced with fibres to full depth. The concrete composition for all the elements was as follows cement - 350 kg/m, water-cement ratio 0.6 and maximum grain diameter 10 mm. At the time of testing, after 6 months ageing, the concrete cube strength was 37 MPa. The fibres were smooth, straight, without curved ends, 20 mm long and with 0.2 mm cross-section diameter. The volume contents of fibres was 1.5%. The bar... 

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