21-11-2012, 06:31 PM
Development of the Weaving Machine and 3D Woven Spacer Fabric Structures for Lightweight Composites Materials
Development of the Weaving Machine.pdf (Size: 5.55 MB / Downloads: 113)
Introduction
Textile manufacturing is a very ancient craft, with a history almost as mankind as itself.
Textile products play a vital role in meeting man's basic needs. Textiles are also important in
all aspects of our lives from birth to death. As well as providing protection from the elements,
the first textiles were used as decoration, providing status for the owner. They were also
used as tools, bags for transporting belonging and for holding food as it was gathered.
Textiles are produced in almost every country of the world, sometimes for consumption
exclusively in the country of the world, sometimes mainly for export. From cottage industry to
Multi-national Corporation, textiles and clothing are truly global industries and it plays a vital
part in the creation of a modern manufacturing economy. In the last 40 years, the
development of technical textiles has attracted the attention of scientists and technologists
since it is expected to exhibit interesting properties opening new fields of application.
The development of man-made fibers and new dyestuffs in the early part of the 20th century,
and continuing technological development, have and continue to lead to new products and
applications. Man-made fibers opened up completely new application areas for technical
textiles. Synthetic fibers offered high strength, elasticity, uniformity, chemical resistance,
flame resistance and abrasion resistance among other things. Applications of new chemicals
help the design engineers to tailor their products for special uses. New fabrication techniques
also contributed to the improved performance and service life of technical textiles the
technological advances of textiles affect in various industries. The application of textile
material in technical textiles has given an impetus to fiber technology. Technical textiles have
met the various challenges created by the advancement of the society and by the ever needs
of mankind which had been supposed to be increased now, at the beginning of the 21st
century /1/.
Knowledge of a basic textile skill of manipulating fibers, fabrics and finishing techniques is
must for an understanding of how all those interact and perform in different combinations and
environments. Beyond that, much of the technology and expertise associated with the
industry resides in an understanding of the needs and dynamics of many very different enduse
and market sectors. Technical textiles materials and products manufactured primarily for
their technical and performance properties rather than their aesthetic or decorative
characteristics /2/.
Fiber-reinforced composites
Fiber-reinforced composites (or fibrous composites) are the most commonly used form of the
constituent combinations. The fibers of such composites are generally strong and stiff and
therefore serve as the primary load-carrying constituent. The matrix holds the fibers together
and serves as an agent to redistribute the loads from a broken fiber to the adjacent fibers in
the material when fibers start failing under excessive loads. This property of the matrix
constituent contributes to one of the most important characteristics of the fibrous composites,
namely, improved strength compared to the individual constituent .
Woven fabrics that are used in composites can be grouped as two-dimensional (2-D) and
three dimensional (3-D) structures. 2D-weaving is a relatively high-speed economical
process. However, woven fabrics have an inherent crimp or waviness in the interlaced yarns,
and this is undesirable for maximum composite properties /10/.
Prepreg
A prepreg is a textile structure that is impregnated with uncured matrix resin. There are
various forms of prepregs such as unidirectional and multi-directional tape prepregs and
woven fabric prepregs. Common fibers that are used for prepregs are carbon, fiberglass and
aramid. Fig. 2.7 shows a schematic of a typical prepreg machine for unidirectional tape
prepreg. Fibers are wound and collimated as a tape. The matrix resin is heated to reduce
viscosity and dispersed on the fibers. The prepreg is calendered for uniform thickness.
Prepregs are suitable for hand and machine lay-up. Fig. 2.8 shows uni- and multi-directional
lay-ups. Increasing the number of oriented plies increases the isotropic strength. Four ply
directions, i.e., 0o/90o/+45o/-45o orientations are considered to be sufficient for isotropic
properties.