Multiple Necking Research Articles

Multiple Necking of Fibre in Single Tungsten Fibre Composites

AbstractMechanisms of multiple necking and deformation of fibre composites have been studied, using single tungsten fibre composites prepared by a plating method. It is concluded that the multiple necking results from local transfer of load from fibre to surrounding matrix. Processes of plastic deformation of the compositesat various stagesare discussed, and the characteristics of each stage are described. Neck spacing with 2–6% elongation decreased with increase in elongtion but remained constant above 6% elongation. Multiple necking occurred when the volume fraction of fibre was smaller than a critical value. The critical value determined. for each composite indicated that a strong matrix yielded large critical value.

Multiple necking phenomena in metal composites: Schoene, C. and Scala, E. Metallurgical Transactions, Vol 1, No 12, pp 3466 - 3468 (December 1970)

Multiple necking phenomena in metal composites: Schoene, C. and Scala, E. Metallurgical Transactions, Vol 1, No 12, pp 3466 - 3468 (December 1970)

Multiple necking of tungsten fibers in a brass-tungsten composite

A model composite system, brass-tungsten, was used to study the effect of multiple necking of metal fibers, strain rate, and fiber surface condition on the ductility and deformation behavior of uniaxial metal matrix composites. Low volume percent (<20 vol pct) composites were made using brass (90 Cu-10 Zn) powders and tungsten wires. Tungsten wires contained in plastically deformed composites exhibited numerous necks per length of wire, with an average spacing between necks of 3 to 5 wire diameters. Composite ductility was shown to increase with decreasing multiple neck spacing and increasing percent reduction-in-area at the necks and was generally independent of strain rate. The multiple necking of tungsten wires in a brass matrix was found to result from local strain hardening of the brass matrix in the vicinity of each neck enabling the matrix to control composite deformation locally. Degrading the brass-tungsten interfacial bond by electropolishing the tungsten wires and coating them with graphite had no effect on the multiple necking phenomenon and composite ductility.

Étude de l'étirage à froid des fibres de polymères synthétiques dans les agents organiques

AbstractThe cold drawing of synthetic polymers is generally carried out through necking at a short collar between the drawn part and the undrawn part of the fiber; if the drawing is carried out in certain organic liquids, the lengthening is realized through thousands of simultaneous necks which permit the fiber to be penetrated by a dye dissolved in the liquid. The stress–strain curves for the drawing in liquid show an important decrease in the force at the time the multiple necking are produced. This decrease is the result of an increase in the mobility of the macromolecular chains through the penetration of the organic liquid to the level of the shoulder of the necks. A morphological study has been carried out through the observation of cuts by optical microscopy, along with a utilization of the techniques of x‐ray diffraction, IR spectroscopy, and electron microscopy. It was found that the liquid penetrates t̀he fiber to the level of the necking via a rupture of the interchain bonds which takes place during the change of structural following the drawing. The bonds are maintained ruptured as long as the liquid is not squeezed out by the aligning of the chains; they reform later to produce a new highly crystalline structure.