Alignment—continued

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 ... 

Generally, the thermal interaction of spheres that can occur at high volume fractions is negligible, such that the simpler Eq. (4.48) is often used. For nonspherical reinforcement, such as aligned, continuous hbers, the thermal conductivity is anisotropic—that is, not the same in all directions. Rayleigh showed that the effective thermal conductivity along the direction of the fiber axis is... 

The main functions of the matrix in a fiber-reinforced composite are to bind the fibers and to transfer loads to and between them only a small amount of the applied load is supported by the matrix. Let us consider a bunch of unidirectionally aligned continuous fibers subjected to a tensile stress. If a fiber breaks down, it becomes useless but if the fibers are embedded in a polymer matrix (see Fig. 15.1a), the load distributes around the break point and the fiber remains useful. Furthermore, the matrix protects the fibers from self-abrasion and scratches on handling, keeps the reinforcement in... 

The combined use of continuous-glass-strand mat as a core material and uniformly and monoaxially aligned continuous-glass fiber as the surface material has also been proposed (5, 25). The incorporation of expanded polystyrene copolymers into composites was proposed for shock-absorbing composites, such as bumper beam cores, knee bolsters, etc. (17, 18). 

Polymer matrix composites (PMCs), or fiber-reinforced plastics (FRPs). provide a wide range of properties and behavior. Materials with discontinuous fibers are slightly stiffer than conventional unreinforced plastics, whereas the fully aligned continuous fiber systems can record exceptionally high specific properties (property divided by density), exeeeding those of competing materials such as steel and aluminum. There are a virtually infinite number of materials, and material formats that can be combined to form a composite material, as shown in Table 1. 

Pultruded rods, reinforced with aligned continuous fibres, are produced as follows (percentages given are fibre volume fractions) ... 

For a oonqx)site material reinforced with aligned continuous fibres, show that Poisson s ratio may be estimated by a q>lying the rule of mixtures ... 

A sheet of composite material consists of aligned continuous fibres in an isotropic matrix. A tensile specimen is cut from the sheet at angle 0 to the fibres. Show that the tensile modulus E of the specimen will vary with 6 as follows ... 

Show that the coefficients of linear thermal expansion for a composite material reinforced with aligned, continuous isotropic fibres may be estimated from... 

For a composite material consisting of aligned, continuous, ductile fibres in a relatively more brittle matrix, show that the axial tensile strength can be estimated from the greater of the following two... 

A composite sheet consists of 50% (by volume) aligned continuous carbon fibres (high-strength form) in an epo matrix. In use, the sheet is to be subjected to tension at various angles 6 to the fibre direction. Describe how the mode of failure will vary with 6, and predict the ranges of d over which each fiulure mode will be observed. (Take cr = 40 MPa and t 2 = 70 MPa.)... 

The solid line in Figure 8 is a least squares fit of the data. It has a slope of 0.92 and an intercept of 0.28 o strain. This line reflects the average behaviour of the fibres during deformation. The dashed line in Figure 8 has a slope of unity and corresponds to e = e which would be the behaviour expected from the Cox model (r8) r an ideal uniaxially-aligned continuous fibre composite with no complication due to thermal stresses. The experimental line confirms that the surface fibres are on average subjected to a thermal compressive strain of 0.287. if it is assumed that the linear dependence of peak position upon e shown in... 

First, consider the case of fibres which are so long that the effects of their ends can be ignored. A block of polymer reinforced with uniaxially aligned continuous fibres is sketched in Fig. 6.10. Three orthogonal axes 1, 2, and 3 are defined within it. When loads are applied to the block we can assume that it deforms as if the mechanical coupling between fibres and matrix took special... 

An element composed of brittle matrix and aligned continuous fibres may be considered as a two-component model subjected to uniform loading, as shown in Figure 8.9. 

The main types of reinforcements used in composite materials include aligned continuous fibers, discontinuous fibers, whiskers (elongated single crystals), particles, and numer-... 

Aligned continuous fiber PMC tubes combine strength and rigidity to make very light structural members and trusses. Porsche and other automobile manufacturers are experimenting with carbon fiber PMC tubular frames to lighten their cars. The Porsche Carrera GT is built with a carbon fiber panel monocoque body on a carbon PMC subframe with practically no metal parts in the structure. 

Table 4.2 Theoretical energy absorbed by aligned continuous fibre composites, as calculated by Eqs 4.89 to 4.91 (after Hibbert and Hannant [74]) ...

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