Properties of fibres

Table 23.4 Some physical properties of fibre-resin preform sheet ...

Nowadays the major thermosetting resins used in conjunction with glass fibre reinforcement are unsaturated polyester resins and to a lesser extent epoxy resins. The most important advantages which these materials can offer are that they do not liberate volatiles during cross-linking and they can be moulded using low pressures at room temperature. Table 3.1 shows typical properties of fibre reinforced epoxy. 

A wide variety of thermoplastics have been used as the base for reinforced plastics. These include polypropylene, nylon, styrene-based materials, thermoplastic polyesters, acetal, polycarbonate, polysulphone, etc. The choice of a reinforced thermoplastic depends on a wide range of factors which includes the nature of the application, the service environment and costs. In many cases conventional thermoplastic processing techniques can be used to produce moulded articles (see Chapter 4). Some typical properties of fibre reinforced nylon are given in Table 3.2. 

The viscoelastic nature of the matrix in many fibre reinforced plastics causes their properties to be time and temperature dependent. Under a constant stress they exhibit creep which will be more pronounced as the temperature increases. However, since fibres exhibit negligible creep, the time dependence of the properties of fibre reinforced plastics is very much less than that for the unreinforced matrix. 

R. Hill, Theory of Mechanical Properties of Fibre-Strengthened Materials - III. Self-Consistent Model, Journal of the Mechanics and Physics of Solids, August 1965, pp. 189-198. 

Modified PAN fibres have been obtained from copolymers containing up to 15% or ISP units using the wet spinning process30. Some properties of modified fibres are presented in Table 1. For comparison are also given the properties of fibres obtained from copolymers additionally crosslinked with conventional crosslinking agents used in the vulcanization of nitrile rubbers. 

Some of the properties of fibres obtained from PAN and from AN copolymers modified with acqueous solutions of ammonium sulfide are shown in Table 3. 

Kharazipour, A., Bergmann, K., Nonninger, K. and Hiittermann, A. (1998). Properties of fibre boards obtained by activation of the middle lamella of wood fibres with peroxidase and H2O2 before conventional pressing. Journal of Adhesion Science and Technology, 12(10), 1045-1053. 

It is evident that fibre geometry and biodurability are the decisive criteria for the carcinogenic properties of fibres. However, there are differing opinions between fibre manufacturers and occupational health and safety experts in the EU and Germany concerning the examination and measuring methods and the evaluation of the carcinogenic properties. 

The properties of fibre-reinforced composites are for example determined by a) length, diameter, orientation, volume fraction and properties of the fibres, b) the properties of the matrix and c) the nature of the bond between fibre and matrix. The ratio between length and diameter is an important fibre property. A small diameter means that the area is also small and consequently there is less chance of defects occurring in that area and so less chance of the fibre breaking. 

A special property of glass is that it can be drawn into fine fibres when it is in plastic state. Glass fibres combine the properties of fibres (they can be woven into cloth) with the properties of glass (they are bad conductors of heat and electricity). 

Properties of fibre-reinforced glass/glass-ceramic matrix composites... 

Oat, Avena sativa, is a cereal which has been little studied, at least from a flavor point of view. Only a few investigations have been published, e.g. by Heydanek and McGorrin (7, 8). A review concerning oat flavor chemistry has also appeared quite recently (9). However, this cereal has attracted increased interest during the last few years, owing to the health benefits of oat. Examples are its cholesterol-lowering properties, the desirable physiological properties of fibre content and the favourable ratio of polyunsaturated to saturated fats in its lipid content (10). 

The mechanical properties of fibres and yams are quite complex and have been the subject of much experimental work. A stressed fibre is a very complicated viscoelastic system in which a number of irreversible processes, connected with plasticity, can take place. 

The most important mechanical properties of fibres and filaments are ... 

The theoretical treatment of the mechanical properties of fibres is, as a matter of fact, more complicated than that of isotropic polymers. Instead of two elastic parameters, e.g. the tensile modulus and the Poisson ratio, we now need five, because of the anisotropy. 

In this respect also the time needed for creep failure, t / is also an important property of fibres. According to Northolt et al. this lifetime reads... 

Occurrence, formation, structure and reactions. Wiley-Interscience, New York,. 597-637 Gummerus M (1985) Sulphite treatment of TMP rejects. Part 1. Properties of fibre fractions at various freeness levels and their influence on the reject pulp. Pap Puu 11 635-647 Heitner C, Hattula T (1988) Ultra-high-yield pulping. Part VI The effect of sulphonation on the development of fibre properties. J Pulp Pap Sci 14 J6-J11 James AN, Tice PA (1965) The presence of carboxyl groups in lignosulfonate preparations. Tappi 48 239-244... 

The surface properties of cellulose, wood fibre, and naper are of great importance in the production and utilization of paper and board. Phenomena as diverse as the formation of fibre-fibre bonds in papermaking and the ink-paper interaction during printing processes are certainly influenced by the surface properties of fibres and sheet. With the development of increasingly sophisti-... 

Effect of Relative Humidity on the Surface Area of Paper. Virtually all the physical and mechanical properties of fibres and paper vary strongly with moisture content, and it would be expected that surface properties should also be sensitive to relative humidity. Little work has been published on the effect of moisture on the surface properties of fibres and paper. As a starting point, it may be noted that the basic property of any surface is its surface area. How does the surface area of a fibre or paper sheet change with relative humidity ... 

Wool fibres may be subjected to fullering - the fibres are treated with an appropriate agent (traditionally mercury compounds were used), which causes the individual scales on the fibre to stand proud of the surface, causing adjacent fibres to become entangled, and increasing the bulk of the material. The process can be employed to make non-woven woollen textiles (i.e. felt), but is also employed to modify the properties of fibres used for yarns and fabrics, and can give a durability to wool fabrics that is not found in the individual fibres. 

Here is an example of how one can use the Universal Mapping Property of fibre products to prove something tangible ... 

P. T. Curtis (1988). CRAG test methods for the measurement of engineering properties of fibre reinforced plastics. 3d ed., RAE TR 88012. ... 

Table 15.1 Properties of fibres used in ropes (mainly from McKenna et al., 2004)...

We also had to be proficient at design and here our capabilities in Finite Element Analysis were important. We use finite element stress analysis for design of offshore structures for oil production, for pipelines and for a range of process plant. By working closely with materials scientists who understand the properties of fibre reinforced materials it was possible to build models of the blocker door and predict load paths and deflections as required by the customer. These analyses formed the basis for determining the shapes and fibre directions of the preforms. 

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