Fiber reinforcements distribution

Strength. Prediction of MMC strength is more compHcated than the prediction of modulus. Consider an aligned fiber-reinforced metal-matrix composite under a load P in the direction of the fibers. This load is distributed between the fiber and the matrix ... 

The formation of a fibrillar structure in TLCP blends makes the mechanical properties of this kind of composites similar to those of conventional fiber reinforced thermoplastics [11,26]. However, because the molecular orientation and fibrillation of TLCPs are generally flow-induced, the formation, distribution, and alignment of these droplets and fibers are considerably more processing-dependent. We do not know ... 

A discontinuous fiber composite is one that contains a relatively short length of fibers dispersed within the matrix. When an external load is applied to the composite, the fibers are loaded as a result of stress transfer from the matrix to the fiber across the fiber-matrix interface. The degree of reinforcement that may be attained is a function of fiber fraction (V/), the fiber orientation distribution, the fiber length distribution, and efficiency of... 

Fiber-reinforced plastics differ from many other materials because they combine two essentially different materials of fibers and a plastic into a single composite. In this way they are somewhat analogous to reinforced concrete, that combines concrete and steel. However, in the RPs the fibers are generally much more evenly distributed throughout the... 

The initial evaluation showed that utilizing fiber-reinforced polymer (FRP) for pipelines is a feasible alternative to steel pipelines with regard to performance and cost [35]. From the cost analysis, an FRP pipe is quite attractive, especially in the regional or distributed service. Currently, spoolable piping manufacturers could install a composite pipeline for serving a 100,000 population for a cost of 250,000-500,000/mi. (does not include the cost for right-of-way), which is well below the DOE s capital cost target in 2017 of 800,000/mi. [35]. From this estimate and cost analyses, it is seen that FRP pipe economics is very attractive, especially for the distribution service. 

Fu, S. and Lauke, B Effects of fiber length and fiber orientation distributions on the tensile strength of short-fiber-reinforced polymers, Composites Sci. Technol., 56, 1179 (1996). 

Wetherhold, R. C., Statistical distribution of strength of fiber-reinforced composite materials, Polym. Composites, 7, 116 (1986). 

There are many ways to classify composites, including schemes based upon (1) materials combinations, such as metal-matrix, or glass-fiber-reinforced composites (2) bulk-form characteristics, such as laminar composites or matrix composites (3) distribution of constituents, such as continuous or discontinuous or (4) function, like structural or electrical composites. Scheme (2) is the most general, so we will utilize it here. We will see that other classification schemes will be useful in later sections of this chapter. 

The effect of fiber diameter on the tensile strength of a glass-fiber-reinforced polystyrene composite is shown in Figure 5.100. Some reinforcements also have a distribution of fiber diameters that can affect properties. Recall from the previous section that the fiber aspect ratio (length/diameter) is an important parameter in some mechanical property correlations. 

Figure 7.89 Temperature distribution along the length of a pultrusion die. Reprinted, by permission, from P. K. Mallick, Fiber-Reinforced Composites, p. 350. Copyright 1988 by McGraw-Hill.

Fiber Length Distribution, for industrial applications, the fiber length and length distribution are of primary importance because they are closely related to the performance of the fibers in matrix reinforcement. Representative distributions of fiber lengths and diameters can be obtained through measurement and statistical analysis of microphotographs fiber length distributions have also been obtained recently from automated optical analyzers. 

Here, 7 is the magnitude of the strain rate tensor and C/ is a phenomenological coefficient which models the interactions between the fibers, usually referred to as the Folgar-Tucker interaction coefficient. The coefficient varies between 0, for a fiber without interaction with its neighbors, and 1, for a closely packed bed of fibers. For a fiber reinforced polyester resin mat with 20-50% volume fiber content, CV is usually between 0.03 and 0.06. When eqn. (8.153) is substituted into eqn. (8.152), the transient governing equation for fiber orientation distribution with fiber interaction built-in, becomes... 

Resin Transfer Molding (RTM). Reinforcing fibers are distributed uniformly in the mold and the mold is closed. Liquid resin is injected into the mold until the excess comes out of the vents. The mold is pressed and heated, similarly to preform molding, until cure is complete. 

Centrifugal Casting. Reinforcing fibers are distributed inside a circular mold. The mold is rotated, and liquid resin is distributed inside it to impregnate the fibers. Rotation of the assembly is continued inside an oven until it is cured. This process is used for making pipes, tanks, and hoops. 

Fig. 9.2 Threshold for long-term creep of a uniaxially reinforced composite as a function of the Weibull modulus for the fiber strength distribution.

Stress Distribution and High Temperature Creep Rate of Discontinuous Fiber Reinforced Metals, Acta Metallurgies et Materialia, 38, 1941-1953 (1990). 26. A. G. Evans, J. W. Hutchinson, and R. M. McMeeking, Stress-Strain Behavior of Metal Matrix Composites with Discontinuous Reinforcements, Scripta Metallurgica et Materialia, 25, 3-8 (1991). 

As mentioned earlier, suspensions of particulate rods or fibers are almost always non-Brownian. Such fiber suspensions are important precursors to composite materials that use fiber inclusions as mechanical reinforcement agents or as modifiers of thermal, electrical, or dielectrical properties. A common example is that of glass-fiber-reinforced composites, in which the matrix is a thermoplastic or a thermosetting polymer (Darlington et al. 1977). Fiber suspensions are also important in the pulp and paper industry. These materials are often molded, cast, or coated in the liquid suspension state, and the flow properties of the suspension are therefore relevant to the final composite properties. Especially important is the distribution of fiber orientations, which controls transport properties in the composite. There have been many experimental and theoretical studies of the flow properties of fibrous suspensions, which have been reviewed by Ganani and Powell (1985) and by Zimsak et al. (1994). 

Gouadec, G., Colomban, R, and Bansal, N.R, Raman study of Hi-nicalon fiber reinforced celsian composites. Rart I Distribution and nanostructure of different phases, J. Am. Ceram. Soc., 84, 1129, 2001. 

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... 

Polymer-based multicomponent systems are abundant in many applications. The properties and performance of particulate-filled systems, such as elastomers and impact modified polymers, and also polymer blends, block copolymers, and fiber reinforced systems, depend to a large extent on the distribution of the components. Hence the local analysis of these distributions down to sub-100 nm length scales (dictated, e.g., by the size of primary filler particles) is of considerable significance. Materials contrast in several AFM approaches offers the possibility to address these issues directly at the surface of specimens or on bulk samples that have been prepared correspondingly. 

Applications. Nondestructive method of determination of carbon fiber reinforced composites. Damage of woven fiber reinforced composites, distribution of filler due to flow in molding techniques, distribution of fiber in composite, and dispersion of carbon black are examples characterizing potential applications of the method. 

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