Elastic fibers, composition

Fiber-reinforced composite materials such as boron-epoxy and graphite-epoxy are usually treated as linear elastic materials because the essentially linear elastic fibers provide the majority of the strength and stiffness. Refinement of that approximation requires consideration of some form of plasticity, viscoelasticity, or both (viscoplasticity). Very little work has been done to implement those models or idealizations of composite material behavior in structural applications. 

Fiber/composite Elastic modulus (GPa) Tensile strength (GPa) Density (g/cm ) Specific stiffness (MJ/kg) Specific strength (MJ/kg)... 

The first elastomeric protein is elastin, this structural protein is one of the main components of the extracellular matrix, which provides stmctural integrity to the tissues and organs of the body. This highly crosslinked and therefore insoluble protein is the essential element of elastic fibers, which induce elasticity to tissue of lung, skin, and arteries. In these fibers, elastin forms the internal core, which is interspersed with microfibrils [1,2]. Not only this biopolymer but also its precursor material, tropoelastin, have inspired materials scientists for many years. The most interesting characteristic of the precursor is its ability to self-assemble under physiological conditions, thereby demonstrating a lower critical solution temperature (LCST) behavior. This specific property has led to the development of a new class of synthetic polypeptides that mimic elastin in its composition and are therefore also known as elastin-like polypeptides (ELPs). 

Ceramic-matrix fiber composites, 26 775 Ceramics mechanical properties, 5 613-638 cyclic fatigue, 5 633-634 elastic behavior, 5 613-615 fracture analysis, 5 634-635 fracture toughness, 5 619-623 hardness, 5 626-628 impact and erosion, 5 630 plasticity, 5 623-626 strength, 5 615-619 subcritical crack growth, 5 628—630 thermal stress and thermal shock, 5 632-633... 

Asloun, El. M., Nardin, M. and Schultz, J. (1989). Stress transfer in single-fiber composites Effect of adhesion, elastic modulus of fiber and matrix and polymer chain mobility. J. Mater. Sei. 24, 1835-1844. 

Fisher, S. and Marom, G. (1984). A complete elastic-plastic analysis of Aramid fiber composites. Composites Sci. Technol. 20, 91-98. 

Pagano, N.J. and Tandon, G.P. (1988). Elastic response of multi-directional coated fiber composites. Composite Sci. Technol. 31, 273-293. 

For example, there are several reports that indicate many of the previously reported changes in elastin composition during atherosclerosis are related to the methods used in the initial isolation of the elastins (52,53). Although in certain forms of emphysema there appears to be evidence that elastic fibers are destroyed, the data related to compositional changes and alter-... 

The exact laws, based on continuum analysis of the fibers and the matrix, would be very complicated. The analysis would involve equilibrium of stresses around, and in, the fibers and compatibility of matrix deformation with the fiber strains. Furthermore, end and edge effects near the free surfaces of the composite material would introduce complications. However, a simplified model can be developed for the interior of the composite material based on the notion that the fibers and the matrix interact only by having to experience the same longitudinal strain. Otherwise, the phases behave as two uniaxially stressed materials. McLean5 introduced such a model for materials with elastic fibers and he notes that McDanels et al.6 developed the model for the case where both the fibrous phase and the matrix phase are creeping. In both cases, the longitudinal parameters are the same, namely... 

A hydrostatic stress can be superposed, but it is caused only by elastic volumetric strain of the composite. The result in Eqn. (39) is, perhaps, not very useful since it is rare that a steady strain rate will be kinematically imposed. When both fiber and matrix creep, the steady solutions for a fixed stress in isothermal states are quite complex but can be computed by numerical inversion of Eqn. (39). The solution can, however, be given for the isothermal case where the fibers do not creep. (For non-fiber composites, this should be... 

Linear elastic fracture mechanics (LEFM) approach can be used to characterize the fracture behavior of random fiber composites. The methods of LEFM should be used with utmost care for obtaining meaningful fracture parameters. The analysis of load displacement records as recommended in method ASTM E 399-71 may be subject to some errors caused by the massive debonding that occurs prior to catastrophic failure of these composites. By using the R-curve concept, the fracture behavior of these materials can be more accurately characterized. The K-equa-tions developed for isotropic materials can be used to calculate stress intensity factor for these materials. 

Paper chromatography was used hy Bowes and Kenten (1949) to examine the amino acid composition of elastin preparations from ligamentum nuchae and skin. The results indicated either that the elastic fibers of skin differ from those of ligamentum nvchac in amino acid composition or that they are less resistant to hot water. This interesting suggestion does not appear to have been pursued. 

The state of combination of the lipids of the human aortic wall has attracted great interest in the past few years because of its significance in theories of the origin of the lipid material in the atherosclerotic plaque. Much work has also been reported on changes in the composition of the extractable lipids of the media, but these compounds, although important in the study of the development of atherosclerosis do not directly affect the elastic fiber and must be regarded as outside the scope of this review. 

Lang RW (1984) Applicability of linear elastic fracture mechanics to fatigue in polymers and short-fiber composites. PhD-Dissertation, Lehigh University, Bethlehem, PA... 

Fig. 3.1 Composition of the connective tissue extracellular matrix. Collagen fibers, maroon Elastic fibers, green Hyaluronan-proteoglycan matrix, gray. Fibroblasts, a macrophage, a mast cell, and a capillary containing a red blood cell are also shown (Modified from Fig. 19-34 in The Molecular Biology of the Cell. B. Alberts et al., 4th Ed. 2002. Garland Science, Taylor Francis Group, NY)...

Table 3.4 Composition of three major types of elastic fibers...

In order to match the safety issues, future pressure vessels include three layers an inner polymer liner, overwrapped with a high-strength and high-elasticity carbon fiber composite, and an outer layer of an aramid-material capable of withstanding mechanical and corrosion damage [107],... 

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