Reinforcement fiber lengths

Nonoxide fibers, such as carbides, nitrides, and carbons, are produced by high temperature chemical processes that often result in fiber lengths shorter than those of oxide fibers. Mechanical properties such as high elastic modulus and tensile strength of these materials make them excellent as reinforcements for plastics, glass, metals, and ceramics. Because these products oxidize at high temperatures, they are primarily suited for use in vacuum or inert atmospheres, but may also be used for relatively short exposures in oxidizing atmospheres above 1000°C. 

More detailed discussion on the interface of fiber length is given in Section X, Theory and Mechanics of Reinforcement. 

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 glass-reinforced plastic tanks, 24 299 Fiber grating, 11 150-151 Fiber length (FL), 18 148 Fiber manufacture, sodium bisulfite in, 23 673 Fiber-matrix bonding, 26 771-772 Fiber modification, chemical, 16 14 Fibernodes, 11 595 Fiber-optic probes, 16 524 Fiber optics, 11 128-162, 15 469 attenuation in, 11 132-133 dispersion in, 11 134-135 fiber drawing in, 11 141-145 fiber strength in, 11 141-145 history of, 11 128-131 inside processes for, 11 136-140 near-infrared, 23 141 optical amplifiers with, 11 145-146 optical fiber fabrication for,... 

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). 

Thomason JL, Vlug MA. Influence of fiber length and concentration on the properties of glass fiber-reinforced polypropylene 1. Tensile and flexural modulus. Composites Part A Applied Science and Manufacturing. 1996 27(6) 477-84. 

Ohsawa, T., Nakayama, A., Miwa, M. and Hasegawa, A. (1978). Temperature dependence of critical fiber length for glass fiber-reinforced thermosetting resins. J. Appl. Polym. Sci. 22, 3203-3212. 

Fibers that have a length greater than this critical length are called continuous fibers, while those that are less are called discontinuous or short fibers. Little transference of stress and thus little reinforcement is achieved for short fibers. Thus, fibers whose lengths exceed the critical fiber length are used. 

The second factor that affects performance in discontinuously reinforced FMCs is fiber length. This has an effect primarily on the ease with which the composite can be manufactured. Very long fibers can create difficulties with methods used to create discontinuously reinforced FMCs and can result in nonuniform mechanical properties. The third factor is also related to fiber geometry, namely, the fiber shape. Recall that the... 

The performance characteristics of a composite material depend on the type of reinforcing fiber (its strength and stiffness), its length, fiber volume fraction in the matrix, and the strength of the fiber-matrix interface. The presence of voids and the nature of the matrix are additional but minor factors. 

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. 

Table I lists some properties of SMC and BMC. These are a function of resin composition, reinforcement, and molding conditions atid may be regarded as typical. This will serve as a frame of reference as to the property levels obtained with SMC and BMC. The differences which exist between SMC and BMC in tensile, flexural, and impact strengths are attributable to more than just the difference in glass loading. Fiber attrition arising from the compounding techniques for BMC as well as the shorter input fiber length account for the lower strengths.

Fig. 11.28 The number average fiber length at various axial positions of an injection molding screw. DuPont Alathon 2010 pellets preblended with 3.2 mm chopped fibers and extruded in a 0.75 in diameter, 20.1 L/D, with 3 1 compression ratio extruder. [Reprinted by permission from R. von Turkovich and L. Erwin, Fiber Fracture in Reinforced Thermoplastic Processing, Polym. Eng. Sci., 23, 743 (1983).]... 

Fig. 11.30 Effect of preheating 50% by weight E-glass fiber-filled polyamide pulltruded pellets on fiber lengths at the screw tip of a 300-ton 23.86-oz reciprocating injection molding machine. [Reprinted by permission from C. G. Gogos, C. K. Yoon, and J. Brizzolara, Injection Molding Process Development for Long Fiber Reinforced Thermoplastics, SPE ANTEC Tech. Papers, 40, 384 (1994).]...

---