Page 276 - Handbook of Properties of Textile and Technical Fibres

250 Handbook of Properties of Textile and Technical Fibres

Tension,
bending and buckling
Tension,
bending and twisting

Dyeing
Primarily tension
and finishing
Weaving and
knitting
Tension,
buckling and bending
Spinning
Combing
Tension, Drafting
buckling and bending
Carding
Opening
and cleaning
Ginning and
lint cleaning
Harvesting

Figure 7.9 Different modes of deformation during processing below the breaking point.

cycles in the fiber-to-yarn conversion system by the different mechanical manipula-
tions applied on the fibers from harvesting to spinning as illustrated in Fig. 7.9.
Throughout these processes, the best a machine can do is not to break the fibers as
this will convert them into useless fiber fragments. Yet, some fiber breakage will
inevitably occur as evident by the increase in the percent of short fiber content in
the waste and the output fiber strands after ginning, lint cleaning, opening and clean-
ing, carding, combing, and drawing. In this regard, the static tests of tensile behavior
can only provide general guidelines for establishing the design limits and the
appropriate settings of textile machinery (e.g., rate of opening and cleaning, wire
type, wire density, speeds, fiber feeding systems, and spinning tension). The missing
link, however, is the effect of the repeated loading and unloading of fibers as millions
of high-speed stretch-release cycles are applied during processing.
Many studies investigate the dynamic tensile behavior using the elastic modulus (or
dynamic stiffness) of fiber under high-speed dynamic forces. The elastic modulus
being the first derivative of the stressestrain relationship can provide many useful
information about the dynamic tensile behavior of fibers, particularly via moduluse
stress or modulusestrain relationships (Woo and Postle, 1974). Unlike all other tensile
parameters, the uniqueness of the elastic modulus stems from the fact that it has an