Modulus continued Young

The properties of PAN fibers ( 10 pm diameter) are very dependent on the final heat treatment temperature (HTT). Tensile strength reaches a maximum (3.5 GPa) at a HTT of around 1500°C, and then decreases, while Young s modulus continues to... 

L.A. Smith Callahan, A.M. Ganios, E.P. Childers, S.D. Weiner, M.L. Becker, Primary human chondrocyte extracellular matrix formation and phenotype maintenance using RGD-derivatized PEG-DM hydrogels possessing a continuous Young s modulus gradient, Acta Biomater. 9 (4) (2013) 6095-6104. 

High modulus continuous filament fibers significantly enhance the Young s modulus and tensile strength of polymers. This is illustrated by a simple derivation. If the fibers are all... 

Fig. 12. Young s modulus increase in an aluminum composite with SiC reinforcement volume fraction for different forms of reinforcement A, continuous...

Yajima, S.. Ha.segawa, Y., Hayashi, J., limura, M. (1978). Synthesis of continuous silicon carbide fiber with high tensile strength and high Young s modulus, part I, synthesis of polycarbosilane as precursor. J. Mater. Sci. 13, 2569-2576. 

Jayaraman. K. and Reifsnider, K.L. (1992). Residual stresses in a composite with continuously varying Young s modulus in the fiber/matrix interphase. J. Composite Mater. 26, 770-791. 

The effect of blending LDPE with EVA or a styrene-isoprene block copolymer was investigated (178). The properties (thermal expansion coefficient. Young s modulus, thermal conductivity) of the foamed blends usually lie between the limits of the foamed constituents, although the relationship between property and blend content is not always linear. The reasons must he in the microstructure most polymer pairs are immiscible, but some such as PS/polyphenylene oxide (PPO) are miscible. Eor the immiscible blends, the majority phase tends to be continuous, but the form of the minor phase can vary. Blends of EVA and metallocene catalysed ethylene-octene copolymer have different morphologies depending on the EVA content (5). With 25% EVA, the EVA phase appears as fine spherical inclusions in the LDPE matrix. The results of these experiments on polymer films will apply to foams made from the same polymers. 

Fig. 5. Young s modulus versus temperature in iron. Notice the continuous decrease as a function of temperature. The abrupt change in modulus when bcc iron transforms to fee.

With the advent of nanomaterials, different types of polymer-based composites developed as multiple scale analysis down to the nanoscale became a trend for development of new materials with new properties. Multiscale materials modeling continue to play a role in these endeavors as well. For example, Qian et al. [257] developed multiscale, multiphysics numerical tools to address simulations of carbon nanotubes and their associated effects in composites, including the mechanical properties of Young s modulus, bending stiffness, buckling, and strength. Maiti [258] also used multiscale modeling of carbon nanotubes for microelectronics applications. Friesecke and James [259] developed a concurrent numerical scheme to evaluate nanotubes and nanorods in a continuum. 

While the design of such coatings is straightforward, selection of appropriate materials is not. Usually materials with the properties required for a particular application are not readily available, and some custom laboratory fabrication is necessary. This usually involves selecting a polymer composite which somewhat approximates the required physical properties. Then minor alterations to the chemical constituents or fillers are used on a trial basis and the acoustic properties (some combination of Young s Modulus and damping factor, sound speed, attenuation, density, and front-face reflectivity) of these sample formulations are measured. This continues until a suitable formulation is achieved. 

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