Elastic modulus filaments

For most hydrardic pressure-driven processes (eg, reverse osmosis), dense membranes in hoUow-fiber configuration can be employed only if the internal diameters of the fibers are kept within the order of magnitude of the fiber-wall thickness. The asymmetric hoUow fiber has to have a high elastic modulus to prevent catastrophic coUapse of the filament. The yield-stress CJy of the fiber material, operating under hydrardic pressure, can be related to the fiber coUapse pressure to yield a more reaUstic estimate of plastic coUapse ... 

Anisotropic polymer filaments could be produced by in-situ photopolymerization of oriented acrylate monomers. Ordering of the monomers was achieved by an elongational flow prior to the polymerization process. The produced polymers showed a high elastic modulus and a low thermal expansion coefficient in the direction of the orientation. 

Five-centimeter-diameter tubular samples with a 0.64-cm (4-in.) wall thickness were also prepared to screen epoxy resins for a study of the effects of fiber content and void volume on the allowable stress and elastic modulus of the samples. Samples were made with Type 410AAE fiberglass and an epoxy resin binder. Each was manufactured with helically and circumferentially wound filaments in one of the following patterns (from inner surface layer to outer surface layer) sample 1 o-xxxx-o-xxxx-o. .. and sample 2 xx-oooo-xx-oo-xx. .., where the symbol o represents filaments wound at 88-89 to the pipe axis x represents filaments at 45 . 

When the elastic modulus was determined from the stress-strain curve, it was assumed that there was a distribution of fiber diameters among the different fibers and that the stress-strain behavior of each fiber would be identical.When bundles consisting of more than 5000 filaments were used for the determination of the X-ray modulus,it was difficult to count the number of filaments, to determine the total area by accurately measuring the cross sectional area of each filament and to evaluate the stress applied only to the crystalline region of the dragline consisting of an almost amorphous region. 

Filament orientation (degrees) Ultimate tensile strength Proportional limit Elastic modulus (1(P psi) Poisson s ratio... 

Riggs [17] observed that a fiber with larger diameter filaments, spun from a mesophase pitch tended to elongate, whilst smaller diameter filaments shrank, presumably because they were more highly oriented. The elastic modulus of as spun fibers increased with the draw ratio, but decreased with increasing thermosetting temperature and is attributed to a relaxation effect. 

Janmey, P.A., S. Hvidt, J. Kas, D. Lerche, A. Maggs, E. Sackmann, M. Schhwa, and T.P Stossel, The mechanical properties of actin gels. Elastic modulus and filament motions. J. Biol. Chem., 1994, 269 32503-32513. 

Similarly to case study 2, Fig. 7.23 demonstrates shows the variations of the elastics modulus and yield stress of PLA filaments produced using different temperatures in the extruder using different 3D printers. By fixing the extrusion parameters such as deposition velocity and screw rotation velocity, it is possible to observe that the different temperatures of the extruder nozzle produce strands with different mechanical properties. 

Figure 11-12. Volume variation of a cubic pore versus applied pressure, for different initial deflections of the edges. The curves presented as examples are calculatedfor apore of size L= 100 nm. The thickness of filaments (rods) is d = 5 nm and the elastic modulus is E = 2500 MPa (Pirard, 2000b).

The rheology of networks of cross-linked and bundled F-actin has been shown to exhibit exceptional elastic behaviour that reflects the mechanical properties of individual filaments. The local viscoelasticity has been investigated by microrheology techniques using embedded colloidal probe particles and optical interferometry, or magnetic tweezers. The elastic modulus is a strong function of the actin concentration, thus cross-link density. Actin can be cross-linked to form a network coating the surface of a vesicle. The viscoelastic and deformation properties of actin-coated vesicles has also been examined. 

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