Fibre deformation

The diagram in Fig. 6 on the left shows another interesting effect. Perpendicular to the fibre direction side maxima can be observed. In an ideal CPRP material, all fibres are parallel and isolated each from another. In reality, the manufacturing process leads to a certain fibre deformation and redistribution. Both the fibres within a layer and the fibres of neighbouring layers can contact each other thus causing variations in the eddy current field. This effect can be used for evaluating some matrix and bonding properties. 

Keywords Carbon plastic polyethylene short fibres deformability plasticity, Ifactal dimension. 

The matrix elastically behaves until the fibres deformation to fracture, Figure 3.452 c, According to the equations developed by M.R. Piggot, in the case of a poor adhesion (a < 1) the fracture effort of the composite material is ... 

Fig. 5.65 Dependence of radical concentration [/ ] upon the strain for nylon 6 fibres deformed at room temperature. (Data taken from Becht and Fischer, Kolloid-Z.u.Z. Polymere, 229, (1969) 167.)...

According to data /3/, the AE sources in the fibrous composites are plastic deformation and cracking of the die material, shift stratification on the fibre-die interphase border, fibre destmction and stretching fibres out of the die. 

Deformation of a solution usually either by spreading or by extrusion as used in making cast film and certain synthetic fibres and filaments. 

The first five of these techniques involve deformation and this has to be followed by some setting operation which stabilises the new shape. In the case of polymer melt deformation this can be affected by cooling of thermoplastics and cross-linking of thermosetting plastics and similtir comments can apply to deformation in the rubbery state. Solution-cast film and fibre requires solvent evaporation (with also perhaps some chemical coagulation process). Latex suspensions can simply be dried as with emulsion paints or subjected to some... 

Probably the first to take up this technique for purposes of scientific research was Michael Polanyi (1891-1976) who in 1922-1923, with the metallurgist Erich Schmid (1896-1983) and the polymer scientist-to-be Hermann Mark (1895-1992), studied the plastic deformation of metal crystals, at the Institute of Fibre Chemistry in Berlin-Dahlem in those days, good scientists often earned striking freedom to follow their instincts where they led, irrespective of their nominal specialisms or the stated objective of their place of work. In a splendid autobiographical account of those... 

Typically, a semicrystalline polymer has an amorphous component which is in the elastomeric (rubbery) temperature range - see Section 8.5.1 - and thus behaves elastically, and a crystalline component which deforms plastically when stressed. Typically, again, the crystalline component strain-hardens intensely this is how some polymer fibres (Section 8.4.5) acquire their extreme strength on drawing. 

The total transverse deformation will be the sum of the deformations in the matrix and the fibres... 

In order to understand the effect of discontinuous fibres in a polymer matrix it is important to understand the reinforcing mechanism of fibres. Fibres exert their effect by restraining the deformation of the matrix as shown in Fig. 3.28. The external loading applied through the matrix is transferred to the fibres by shear at the fibre/matrix interface. The resultant stress distributions in the fibre and matrix are complex. In short fibres the tensile stress increases from zero at the ends to a value ([Pg.226]

Up to this stage we have considered the deformation behaviour of fibre composites. An equally important topic for the designer is avoidance of failure. If the definition of failure is the attainment of a specified deformation then the earlier analysis may be used. However, if the occurrence of yield or fracture is to be predicted as an extra safeguard then it is necessary to use another approach. 

Fig. 11. Profiles of orienlation density along the most pronounced <110> fibre of the AlZn78 alloy-samples deformed at different temperatures.

Fibres based on AN copolymers containing 4—10% of monomeric units of JO42 and obtained by wet spinning from solutions in DMF have a much better (2-8 times) resistance to multiple deformations than PAN fibres and have a higher light-fastness than PAN fibres. They are, however, inferior to the latter with respect to abrasive resistance and thermal stability. 

Graft copolymers of PAN with PMA have been synthesized by this method and branched PAN was obtained using AN as the grafted monomer. Fibres obtained from graft copolymers, irrespective of the nature of the grafted component, are superior to PAN fibres as far as their resistance to multiple deformations is concerned. 

Insertion of flexible blocks into the stiff polymer chain of PAN ensures the possibility of raising the resistance of modified PAN fibres to multiple deformations and, especially, increases significantly the abrasive resistance of fibres made of block copolymers. 

One of the main methods for improving the mechanical properties of linear polymers is their drawing that can be uniaxial (fibres), biaxial (films), planar symmetrical (films-membranes) etc. As a result of polymer deformation, the system changes into the oriented state fixed by crystallization. 

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