Short fibers composites, selected

There are no standard test methods specific for discontinuous fiber (or short fiber) reinforced thermoplastics. It is also not clear whether a geometry-independent fracture parameter can be measured for these nonuniformly inhomogeneous materials. However in spite of these reservations there has been considerable work conducted towards characterizing short fiber composites for fracture toughness using the standard and other procedures outlined in the previous sections. The investigators have recognized that fracture mechanics data provide much more reliable information than the customary alternative tests for material selection and also a service performance indicator for components. 

Asbestos fiber identification can also be achieved through transmission or scanning electron microscopy (tern, sem) techniques which are especially usefiil with very short fibers, or with extremely small samples (see Microscopy). With appropriate peripheral instmmentation, these techniques can yield the elemental composition of the fibers using energy dispersive x-ray fluorescence, or the crystal stmcture from electron diffraction, selected area electron diffraction (saed). 

Aramids papers are found in a much broader range of applications than films (see Applications section). Most papers are comprised of a composite structure of short fibers and a binder. Paper properties can be tailored by changing the composition and the processing conditions. Selected properties are illustrated in Table 13.6. 

This section will review selected papers on the behavior of composites reinforced with more or less isotropically dispersed short fibers. More detailed technological and theoretical mechanical discussions, as well as additional information on composites containing continuous unidirectional or cross-plied fibers, is given by Ashton et al. (1969), Broutman and Krock (1967, 1974), Chamis (1974a), Corten (1966, 1971), Hattori (1970), Parkyn (1970), Schwartz and Schwartz (1968), Tsai et al (1969), and Wu (1974), as well as in the general literature. ... 

Extensive reviews on short fibers-reinforced elastomers have been published by Goettler and Shen, ° and more recently by Rajeev. Table 7.11 is a list of selected published works on natural fiber-filled rubber composites, sorted by rubber type. Only vulcanizable rubbers were considered in preparing the table thermoplastic rubber and rubber-plastics blends were omitted. As can be seen most grades of conventional elastomers have been considered with quite a large variety of natural fibers. Natural Rubber, SBR, and EPDM compounds have received much attention, as expected with respect to their industrial importance. A bonding system is us in most cases, with resin types (i.e. resorcinol-formaldehyde, resorcinol-hexamethylenetetramine, sil-ica-resorcinol-hexamethylenetetramine) the most frequent ones. 

Such complex design of smart composite structures connected with the testing necessity of every subsystem requires selection and application of adapted experimental techniques. A short overview of the common techniques enabling characterization of smart fiber-reinforced composites is presented in the following sections. Stimulated by different levels of measurement, the described techniques have been differentiated into quahtative and quantitative ones. 

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