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Composites fibres

Laminate analysis is based upon the principle of strain compatibility, which means that the in-plane strains in neighbouring layers must be equal. The stresses required in each layer to produce a given strain are first calculated from the previously-computed elastic constants of the layer for the appropriate angle to the fibre direction, and then integrated over all layers. The results define the clastic constants of the whole laminate. Simple computer programs take the drudgery out of these calculations. [Pg.350]

The stresses and strains in a unidirectional carbon fibre-epoxy laminate are related by the equations (stresses in GPa) [Pg.351]

Note that this calculation is based on the principle that the strains are the same in both sets of plies, and that stresses are added. Applying the same procedure to the B direction [Pg.351]

Calculate Young s moduli in the principal directions for the unidirectional and cross-plied laminates discussed in the foregoing example. [Pg.351]

The data were given in the form of a stiffness matrix, which can be written Q, where [Pg.351]


Galculate the upper and lower values for the modulus of the composite material, and plot them, together with the data, as a function of Vf. Which set of values most nearly describes the results Why How does the modulus of a random chopped-fibre composite differ from those of an aligned continuous-fibre composite ... [Pg.277]

Fig. 25.1. (a) When loaded along the fibre direction the fibres and matrix of a continuous-fibre composite suffer equal strains, (b) When loaded across the fibre direction, the fibres and matrix see roughly equal stress particulate composites ore the some. ( ) A 0-90° laminate has high and low modulus directions a 0-45-90-135° laminate is nearly isotropic. [Pg.266]

Fig. 25.2. The stress-strain curve of o continuous fibre composite (heavy line), showing how it relates to those of the fibres and the matrix (thin lines). At the peak the fibres are on the point of failing. Fig. 25.2. The stress-strain curve of o continuous fibre composite (heavy line), showing how it relates to those of the fibres and the matrix (thin lines). At the peak the fibres are on the point of failing.
For many applications (e.g. body pressings), it is inconvenient to use continuous fibres. It is a remarkable feature of these materials that chopped fibre composites (convenient for moulding operations) are nearly as strong as those with continuous fibres, provided the fibre length exceeds a critical value. [Pg.267]

Consider the peak stress that can be carried by a chopped-fibre composite which has a matrix with a yield strength in shear of d (d = jd ). Figure 25.4 shows that the axial force transmitted to a fibre of diameter d over a little segment 8x of its length is... [Pg.267]

This is more than one-half of the strength of the continuous-fibre material (eqn. 25.3). Or it is if all the fibres are aligned along the loading direction. That, of course, will not be true in a chopped-fibre composite. In a car body, for instance, the fibres are randomly oriented in the plane of the panel. Then only a fraction of them - about - are aligned so that much tensile force is transferred to them, and the contributions of the fibres to the stiffness and strength are correspondingly reduced. [Pg.269]

M. R. Piggott, Load Bearing Fibre Composites, Pergamon Press, 1980. [Pg.276]

A unidirectional fibre composite consists of 60% by volume of Kevlar fibres in a matrix of epoxy. Find the moduli and Comment on the accuracy of your value for E. Use the moduli given in Table 25.1, and use an average value where a range of moduli is given. [Pg.276]

E ll = composite modulus parallel to fibres = composite modulus perpendicular to fibres Vj = volume fraction of fibres E = Young s modulus of fibres E, = Young s modulus of matrix. [Pg.376]

Epoxide resin laminates are of particular importance in the aircraft industry. It has been stated that the Boeing 757 and 767 aircraft use 1800 kg of carbon fibre/ epoxide resin composites for structural purposes per aeroplane. The resin has also been used with Aramid fibres for filament-wound rocket motors and pressure vessels. The AV-18 fighter aircraft is also said to be 18% epoxide resin/cc bon fibre composite. The resins are also widely used both with fibres and with honeycomb structures for such parts as helicopter blades. [Pg.773]

Epoxide resins reinforced with carbon and Aramid fibres have been used in small boats, where it is claimed that products of equal stiffness and more useable space may be produced with a 40% saving in weight over traditional polyester/ glass fibre composites. Aramid fibre-reinforced epoxide resins have been developed in the United States to replace steel helmets for military purposes. Printed circuit board bases also provide a substantial outlet for epoxide resins. One recent survey indicates that over one-quarter of epoxide resin production in Western Europe is used for this application. The laminates also find some use in chermical engineering plant and in tooling. [Pg.773]

The poor stability on exposure to air and water, particularly at elevated temperatures, which results in a reduction in conductivity, also poses problems. In the case of polypyrrole it has been found that conductivity can, however, be maintained either by the drastic measure of storing under the protective layer of the inert gas argon or embedding polypyrrole film in a matrix of an epoxide resin-glass-fibre composite. [Pg.889]

Multl-directlonal continuous fibre composite (Quasl-lsotroplc)... [Pg.169]

Reinforcing fibres have diameters varying from 7 /im to 1(X) /im. They may be continuous or in the form of chopped strands (lengths 3 mm-50 mm). When chopped strands are used, the length to diameter ratio is called the Aspect Ratio. The properties of a short-fibre composite are very dependent on the aspect ratio - the greater the aspect ratio the greater will be the strength and stiffness of the composite. [Pg.171]

This is an important relationship. It states that the modulus of a unidirectional fibre composite is proportional to the volume fractions of the materials in the composite. This is known as the Rule of Mixtures. It may also be used to determine the density of a composite as well as other properties such as the Poisson s Ratio, strength, thermal conductivity and electrical conductivity in the fibre direction. [Pg.173]

As shown in Fig. 3.4 stress-strain tests on uniaxially aligned fibre composites show that their behaviour lies somewhere between that of the fibres and that of the matrix. In regard to the strength of the composite, Ocu, the rule of mixtures has to be modified to relate to the matrix stress, o at the fracture strain of the fibres rather than the ultimate tensile strength, o u for the matrix. [Pg.175]

Example 3.4 For the PEEK/carbon fibre composite referred to in Example 3.2 calculate the values of V j and Vent if it is known that the ultimate tensile strength of PEEK is 62 MN/m. ... [Pg.177]

The transverse modulus, Ect, may be determined in a matmer similar to that described earlier for the longitudinal modulus. Consider a unidirectional fibre composite subjected to a transverse force, Fct, in the direction perpendicular to the fibre axis. [Pg.177]

Fig. 3.7 shows how the longitudinal and transverse moduli vary with volume fraction for a unidirectional fibre composite. [Pg.179]

Some typical elastic properties for unidirectional fibre composites are given in Table 3.4. [Pg.181]

Example 3.8 A thin unidirectional carbon fibre composite is loaded as shown in Fig. 3.14 and has the properties listed below. If the fibres are aligned at 35° to the x-axis, calculate the stresses parallel and perpendicular to the fibres. [Pg.192]

The previous analysis has shown that the properties of unidirectional fibre composites are highly anisotropic. To alleviate this problem, it is common to build up laminates consisting of stacks of unidirectional lamina arranged at different orientations. Clearly many permutations are possible in terms of the numbers of layers (or plies) and the relative orientation of the fibres in each... [Pg.202]

It is also worthy of note that large values of Poisson s Ratio can occur in a laminate. In this case a peak value of over 1.5 is observed - something which would be impossible in an isotropic material. Large values of Poisson s Ratio are a characteristic of unidirectional fibre composites and arise due to the coupling effects between extension and shear which were referred to earlier. [Pg.217]

Hull also proposed that the shear modulus and Poisson s Ratio for a random short fibre composite could be approximated by... [Pg.232]

El and E2 refer to the longitudinal and transverse moduli for aligned fibre composites of the type shown in (Fig. 3.29). These values can be determined experimentally or using specifically formulated empirical equations. However, if the fibres are relatively long then equation (3.5) and (3.13) may be used. These give results which are sufficiently accurate for most practical purposes. [Pg.232]

Up to this stage we have considered the deformation behaviour of fibre composites. An equally important topic for the designer is avoidance of failure. If the definition of failure is the attainment of a specified deformation then the earlier analysis may be used. However, if the occurrence of yield or fracture is to be predicted as an extra safeguard then it is necessary to use another approach. [Pg.232]

Richardson, M.O.W. Polymer Engineering Composites, Applied Science London (1977). Agarwal, B. and Broutman, L.J. Analysis and Perfonrmnce of Fibre Composites, Wiley Interscience, New York (1980). [Pg.240]


See other pages where Composites fibres is mentioned: [Pg.184]    [Pg.64]    [Pg.144]    [Pg.264]    [Pg.376]    [Pg.515]    [Pg.606]    [Pg.387]    [Pg.9]    [Pg.169]    [Pg.169]    [Pg.169]    [Pg.169]    [Pg.171]    [Pg.172]    [Pg.177]    [Pg.226]    [Pg.227]    [Pg.232]    [Pg.238]    [Pg.338]   
See also in sourсe #XX -- [ Pg.290 ]

See also in sourсe #XX -- [ Pg.290 ]

See also in sourсe #XX -- [ Pg.132 , Pg.154 , Pg.165 , Pg.166 , Pg.167 , Pg.168 , Pg.169 , Pg.170 , Pg.171 , Pg.172 ]




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