Elastic properties composites

Y. Gowayed, G.Ojard, E. Prevost, U. Santhosh, and G. Jefferson, Defects In Ceramic Matrix Composites and their Impact on Elastic Properties, Composites Part B 55 (2013) 167-175. 

In a semicrystalline polymer, the crystals are embedded in a matrix of amorphous polymer whose properties depend on the ambient temperature relative to its glass transition temperature. Thus, the overall elastic properties of the semicrystalline polymer can be predicted by treating the polymer as a composite material... 

Some typical elastic properties for unidirectional fibre composites are given in Table 3.4. 

Fig. 3.24 Variation of elastic properties for a single ply of carbon/epoxy composite...

Donald F. Adams and Stephen W. Tsai, The Influence of Random Filament Packing on the Elastic Properties of Composite Materials, Joumsd of Composite Materials, July 1969, pp. 368-381. 

J. M. Whitney and M. B. Riley, Elastic Properties of Fiber Reinforced Composite Materials, AIAA Journal, September 1966, pp. 1537-1542. 

The calculated Debye temperatures are also listed in Table 3. From this table, it is clear that the elastic properties of the bulk amorphous Pd-Ni-P and Pd-Cu-P alloys change little with changing composition. The elastic moduli of the Pd-Cu-P alloys are slightly lower than those for the Pd-Ni-P alloys. 

The new polymers are intermediate in composition and crystallinity between the essentially amorphous EPR and the semicrystalhne iPP. The presence of the complementary blocks of elastomers for both ethylene and propylene crystallinity should not indicate a similarity, beyond the levels of the crystallinity in the properties of the E-plastomers and the P-plastomers. The E-plastomers and the P-plastomers differ in their stmctural, rheological, as well as their thermal, mechanical, and elastic properties. In a comparison of the tensile strength and tensile recovery (tension set) from a 100% elongation for a range of P-plastomers and E-plastomers, the former have lower tension set than EPR and iPP. However, for comparative E-plastomers and P-plastomers at equivalent tensile strength, the latter have significantly better tension set. In summary, P-plastomers are tough polyolefins which are uniquely soft and elastic. 

After introduction of cross-links in the strained state, the composite network retracts, upon release, to a stress-free state-of-ease (J9 ) The amount of retraction is determined by the degree of strain during cross-linking and by the ratio >i/v2. The elastic properties relative to the state-of-ease are isotropic for a Gaussian composite network ( 8, 1 9,20). 

Therefore, a possible theoretical concept of using such materials in LIB s is based on the development of various composites (alloys), in which the volume variations of the electroactive constituents of AM during cycling can be compensated by the elastic properties of the electrically conductive matrix (Figure 2). 

Hsu and Berzins used effective medium theories to model transport and elastic properties of these ionomers, with a view toward their composite nature, and compared this approach to that of percolation theory. ... 

Three-dimensional distributions of the micro-residual stresses are very complicated, and are affected by the elastic properties, local geometry and distribution of the composite constituents within a ply. Many analytical (Daniel and Durelli, 1962 Schapery, 1968 Harris, 1978 Chapman et ah, 1990 Bowles and Griffin, 1991a, b Sideridis, 1994) and experimental (Marloff and Daniel, 1969 Koufopoulos and Theocaris, 1969 Barnes et ah, 1991 Barnes and Byerly, 1994) studies have been performed on residual thermal stresses, A two-dimensional photoelastic study identified that the sign and level of the residual stresses are not uniform within the composite, but are largely dependent on the location (Koufopoulos and Theocaris,... 

Acoustic microscopy has a special place in this powerful armoury. It depends on the elastic response of the material to acoustic waves, and therefore provides information on local changes in elastic properties thus, for example, it is particularly sensitive to fine cracks (which might not be observable by other techniques). It has already been applied to a wide range of materials, including biological specimens, minerals, semiconductor devices, composites, ceramics, etc. As is the case for all other techniques, it is essential to have a clear understanding of the contrast mechanisms, so that the observations can be interpreted with confidence. This book provides potential users, such as materials scientists and biologists, with a comprehensive account of the basic techniques, of the contrast mechanisms, and of the way the techniques can be applied to obtain information on microstructure in different types of specimen. 

A more detailed discussion of the visco-elastic properties of rubber-like elastomers for composite propellants was recently given in a paper by Landel and T. L. Smith [8]. 

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