TTL733: SELECTED TOPICS IN FABRIC MANUFACTURE

A
Term paper
On

“Braiding”

Submitted to: Submitted by:

Dr.V.K.Kothari Parmar Sanjay.
(2008TTE2881)

DEPARTMENT OF TEXTILE TECHNOLOGY

 “Braiding”

INDIAN INSTITUTE OF TECHNOLOGY, NEW DELHI-16.

CONTENT

1. Introduction................................................................................................2

2. Braiding…………………………………………………………………..2

3. Principle of Braiding……………………………………………………..3

4. Methods of Interlacing…………………………………………………...3

5. Braid repeat………………………………………………………………4

6. Types of braid ……………………………………………………………4

6.1 Circular Braiding………………………………………………...5
6.2 Flat braiding……………………………………………………..6
6.3 Difference between circular braiding and flat braiding…………7

7. Driving arrangement for Horn Gear Carrier……………………………...7

8. Three Dimensional Braiding……………………………………………...8

8.1 Interlock layer –to-layer Braiding………………………………8
8.2 Braiding of Square Braided……………………………………10

9. Core Construction……………………………………………………….11

10. Sheath construction…………………………………………………….11

11. Innovative Braid Technology…………………………………………..11

12. High Elastic Material…………………………………………………...13

13. Important Braid Relationship……………………………………..…...14

14. Effect of braiding parameter on braid properties and structure………...16

15. References……………………………………………………………....17

Indian Institute of Technology, Delhi 2 2008TTE2881

Department of Textile technology
 “Braiding”

1. INTRODUCTION

Braiding is a textile process which is known for its simplicity and versatility. It is
an old technique but experiencing resurgence in interest because of its diverse
applications. A braided structure has many applications ranging from rope, cord, hose
reinforcement covering, composite tube, rotor hubs, to parts in automobile and aerospace
industries using new composite materials. The extension of two dimensional (2D)
braiding to three-dimensional braiding (3D) has opened up new opportunities in the near
net shape manufacturing of high damage resistant structures. Three-dimensional braiding
is one of the textile processes in which a wide variety of complex structural shapes can be
produced in an integrated manner resulting in highly damage resistant structural
preforms, as these preforms can withstand axial, flexural, and torsional loads. One of the
important applications of braided structures is double braided ropes, which consist of two
separable layers, core, and a sheath Particular application. The geometry of the braided
structure depends on a number of parameters like carrier (horn gear) speed, number of
carriers, take-up speed, and mandrel geometry. The braids formed on a braiding machine
can be classified by the type of interlacements i.e., diamond braid (1/1 repeat), regular or
plain (2/2 repeat), and Hercules braid (3/3 repeat) [1]. Similarly braids can be further
classified according to the type of appearance or cross section i.e., flat braid, tubular
braid, and fancy braid [2].

2. Braiding

Braiding is the simplest form of fabric forming and probably it is older than
weaving[1]. The diagonal intertwining of yams forms a braid structure. There are no warp
and filling yams the sense of a woven fabric. Braiding does not require beat-up and
shedding; the yams do not have to go through heddles and reed. Braiding is more
significant for industrial fabrics than consumer textiles. Although the volume of braided
structures is small compared weaving and knitting in consumer textiles, braiding is one of
the major fabrication methods (or) composite reinforcement structures. With increasing
applications of industrial textiles, the use of braided fabrics is also increasing. Traditional
examples of the braid structures for industrial applications are electrical wires and cables,
harnesses, hoses, industrial belts and surgical sutures. Examples of the relatively new
application areas for braiding include reinforcement structures of sporting goods
(baseball bats, golf clubs, water skis, snow skis), aerospace and automotive parts.

The geometry of the braided fabric is directly related to the machinery, which
forms the fabric. By understanding the relationship between the machinery and the yams,
it is possible to construct diagrams, which describe the structure of the braid. Braiding
can be classified as two and three-dimensional braiding. Two-dimensional braid
structures can be circular or flat braids. Three-dimensional braiding is relatively new and
was developed mainly for composite structures. Although circular and flat braids have
thickness, it is small compared to the other two dimensions: therefore, they are
considered as two-dimensional.

Indian Institute of Technology, Delhi 3 2008TTE2881

Department of Textile technology
 “Braiding”

3. Principle of Braiding

The basic principle of braiding as shown in fig 1 consists of two sets of bobbin
moving in different direction. The yams to be braided are wounded onto bobbins that are
moved bodily in a horizontal plane along a serpentine (sinusoidal) path causing the
threads to interface, as they are withdrawn from one point above the bobbins. The title
'maypole' is also attached to the braiders because of the similarity between the maypole
ribbon dancers and the bobbin path in the braiding process.

Fig.1 Principle of Braiding

4. Methods of Interlacing

The main component to form a braid is the carrier containing the strand. Each
carrier is equipped with a foot, which is engaged by one of the slots in the horn gear. A
horn gear is a plate, whose perimeter is slotted at regular intervals. The portion of the
plate between-the slots is termed a horn, there being as many horns as the slots. The
carrier thus is propelled round the part of a guide track controlled by the particular horn
gear. The guide tracks have a slightly elliptical form to facilitate the change over of the
carriers from one disc to the next one. Thus, the general principle is that, the horn gears,
driven by the gear wheels placed in contact all around the machine, move the bobbin
carriers round in the plate racks, in such a way, that each pair of bobbins cross round each
other and then move to the next disc. As mentioned earlier, there are two sets of such
carriers; one set moving clockwise and the other set anticlockwise, round the machine. If
a strand continuously passes over and under two strands of opposing set, it is then
designated as 2/2 braid. Thus there are three braid weaves that have recognized names
and are popular. These are:

 Diamond braid with a 1/1 intersection repeat, as in Fig 2 (a)

 Regular or Plain braid with a 2/2 intersection repeat, as in Fig 2 (b).
 Hercules braid with a 3/3 intersection repeat, as in Fig 2 (c).

Indian Institute of Technology, Delhi 4 2008TTE2881

Department of Textile technology
 “Braiding”

Other simple interlacing in common use includes 2/1 and 3/1 intersection repeats. Of
all these, the regular interlacing is by far the most popular.

Fig.2 Braiding Types

5. Braid Repeat

In a simple braid, a constant number of plaits are required for a strand to leave a
given point and to return to an exactly equivalent position further along the braid. The
number of plaits required to do this is the 'braid repeat, a quantity equal to the number of
strands in a flat braid and to half the number of strands in a tubular braid. A complete
repeat of any braid occurs between the times a carrier leaves any point on the machine
and returns to the identical position Brunnschweiler [4].

6. Types of Braid

Adanur [1] Classified braiding as Two-dimensional and Three-dimensional

braiding. Two dimensional braid structures can be either circular or flat.
Brunnschweiler[2] classifies braids into three self-descriptive headings as Flat braids,
Tubular or Round braids and Fancy braids. Among these, flat and round braids are more
common.

Most machines are built either for one or the other, but there are makers who
design them with interchangeable type. The machine has the same layout in both the
cases, and the only difference is that in circular braid the bobbins continue to move in a
circular path, where as in a flat braid they turn back at a point, forming a kind of
horseshoe movement. Flat braids are made by braiding a longitudinal wire system,
generally in odd numbers, in a given construction and density, Jarmila svevora [3].

On a flat braider, there is one continuous track which all the yam carriers follow
first in a Clockwise direction and then in a counterclockwise direction as they pass round
the point of braid formation, causing their threads to move from one edge of the braid to

Indian Institute of Technology, Delhi 5 2008TTE2881

Department of Textile technology
 “Braiding”

the other and back again. On a tubular braider, as shown in Fig 2(b), half the carriers
move continuously in one direction and the other half in the opposite direction in two
distinct tracks, necessitating an even number of horn gears Brunnschweiler [4].

The three dimensional braiding technology is an extension of the well established

two dimensional braiding technologies. By introducing a third yam orientation parallel to
the braid axis (at time if braiding) a triaxial braid is created provided added bending,
tensile strength and mess to the fabric. It is only variety producing a wide variety of solid
complex structural shapes in an integral manner.

6.1. Circular Braiding [1]

Circular (tubular or round) braids are formed hollow or around a center core. A
circular braiding machine consists of two sets of an even number of spools containing the
braiding yarns. One set runs clockwise around the center of the machine and the other set
turn in counterclockwise direction as shown in Figure 3. While revolving in opposite
directions, the carriers are diverted to pass alternately inside and outside (under and over)
one another. The clockwise and counterclockwise paths cause the two sets of yams to
intersect, thus producing a tubular braid. The yams from the bobbins are collected above
the hub of the circular track in which the bobbins travel. Since the speed of the yam
carriers is constant, the openness of the fabric is changed by changing the take-up speed
of the fabric. Circular braiders are also called ma “maypole" braiders since their motion is
similar to the maypole dance.

The tube can be braided about a central core of yams, thus producing a solid braid
composed of a core and sheath. The core, in fact, can be any shape and material. This is
the reason why circular braiding is widely used in composite preform manufacturing:
unlike weaving or knitting, the braiding structure conforms to the core very well thus
making it easy to develop braided structures of complex shapes. Depending upon the
number of spools (carriers), the nature of the yam, the path of the spools and the core,
endless numbers of braided structures can be produced.

Indian Institute of Technology, Delhi 6 2008TTE2881

Department of Textile technology
 “Braiding”

Fig: 3 Circular Braiding Machines.

The mechanical components of a circular braiding machine can be grouped under

four categories:
 Track plate
 Horn gears
 Spool carrier
 Fabric take-up mechanism

Another type of braiding machine to produce two-dimensional braids is the rotary

machine. The rotary braiding machine is faster than the maypole braider. However, rotary
machines are less versatile in terms of making different shapes and they have less number
of carriers.

6.2. Flat Braiding [1]

Flat braids are made in the form of a flat strip or tape. In flat braiding, instead of
following two Continuous paths, the carriers turn around or reverse direction at two given
points called "terminals" and then continue on the opposite track, Le., the track does not
complete a circle as shown in Figure 4.

The size of a braid is governed by the following factors:

(1) The number of carriers: Tubular braiders have an even number of carriers, and
flat braiders usually have an odd number of carriers. The minimum number of carriers is
three, which gives a basic diamond braid similar to a girl's plaited hair.
(2) The diameter of the yams
(3) The number of yam ends per carrier
(4) The number of yams per unit length

a:- track plate, b:- spool carrier, c:- braiding yarn, d:-braiding point and former, e:- take
off roll with change gear& f:- delivery can

Indian Institute of Technology, Delhi 7 2008TTE2881

Department of Textile technology
 “Braiding”

Fig: 4 Flat Braiding Machine

6.3. Difference between Flat and Circular Braiding

 The total no of carrier in the flat braiding are odd in no.

 The cyclic rotation is not complete as shown in the fig 5.

(a) Flat Braid Motion (b) Circular Braid Motion

Fig: 5 Differences in Braiding Motion

7. Driving Arrangement for Horn Gear and Carrier

Gearwheel Horn gears or disc Bobbin carriers (moving round in the

tracks)

Each carrier equipped with a foot is engaged by one of the slots in the horn gear.
The Carrier thus is propelled round the part of a guide track controlled by the particular
horn gear. The strand from one carrier passes over and under the strand of adjacent
carriers.

A horn gear is a plate as shown in the figure 3.6, whose perimeter is slotted at
regular intervals. The portion of the plate between the slots is termed as horn, there being
as many as the slots. The size of the horn gears affects the yam capacity of the carriers
and, to some extent, the speed of the machine. The smaller the horn gear diameter the
faster the speed of the machine but more frequent is the stop for yarn replenishment due
to small package which it can hold.

Indian Institute of Technology, Delhi 8 2008TTE2881

Department of Textile technology
 “Braiding”

Fig: 6 Horn Gear Driving Arrangement

8. Three-Dimensional Braiding

Three-dimensional braiding is relatively new compared to two-dimensional

braiding. The first 3-D braiding machine was developed in the 1960s. The three-
dimensional braiding concept has been developed mainly for textile structural
composites. There is no three-dimensional braiding machine that is commercially
available. The main reason for this is that every different three dimensional braided
structure requires a different machine with specific characteristics and dimensions.
Therefore, companies and research institutions custom-build their 3-D braiding machines.

A special type of braid for composites, called triaxial braiding, axial yams are
introduced to the structure as shown in Figure 3.7. The axial yams do not interlace or
intertwine with other yams and are trapped between the two sets of yams in the structure.

Fig: 7 Tri-axial Braid

8.1. Interlock Layer-To-Layer Braiding [5]

The conventional 2D braiding (or Maypole braiding) is a simple textile process. It

is composed of two sets of yam carriers rotating on a circular track. One set rotates in the
clockwise direction while the other set rotates in the counterclockwise direction and
interlace the first one to form a tubular preform. The yam carriers move through two

Indian Institute of Technology, Delhi 9 2008TTE2881

Department of Textile technology
 “Braiding”

sinusoidal slots in the track plate by means of horn-gears. Several layers each with a
specified braiding angle can be serially superimposed in order to form a multi-layer braid.
But, the problem of these multi-layer braids consists in the interlaminar weakness or in
other words in its sensitivity to delamination.3D braiding overcomes this problem by
introducing reinforcing yams of materials that transversely connect the different layers
during the process.

The multi-path braiding machine developed by D. Bigaud et al [5] can produce

five-layer interlock braids as shown in fig 3.8. This prototype possesses five crowns of 64
counter-rotating four-slot horn-gears each. And then, 10 different circulation tracks exist
and 320 yarns can be braided simultaneously. A maximum of 320 additional axial yams
could be introduced from the centre of each horn gear. The inter connectivity of the three-
dimensional braided preforms is ensured by using systems of counter rotating horn gears
similar to those found on a conventional 2D braiding machine. But, here, each internal
track is connected not only with its adjacent neighbor on the same crown (or layer) but
also with those producing an adjacent layer of braid. A moving mandrel with a maximum
diameter of 800mm allows the handling of large and heavy core structures for the
formation of braids with complex shapes. The braiding angle ranges from ±10˚ to ±80˚
and, depending on this angle and on the mandrel diameter, the maximum speed
production can reach 1 m/min.

(a) Front view of the braiding machine (b) Detail of the circulation tracks plate

Fig: 8 Interlock braiding machine

Indian Institute of Technology, Delhi 10 2008TTE2881

Department of Textile technology
 “Braiding”

8.2. Braiding of Square Braids [6]

One of the ways of producing three dimensional braiding can be braided my

manipulating the loop of rotation of the carriers. These braids were solid square type and
2 X 2, 2X4, 4X4, 4X6, 4X8ribsas shown in fig 9 & 10.

Fig: 9 Rotary Braiding Machines for Square Braids

Fig: 10 Families of Coupled Square Braids

Indian Institute of Technology, Delhi 11 2008TTE2881

Department of Textile technology
 “Braiding”

9. Core Construction

The core construction has a great effect on load bearing and extensibility and fall
holding capacity of the braided rope in the core. To achieve our fall and elongation
performance goals we need to configure the materials to make sure an Infinity Rope has a
balanced, flexible construction and forms a 'round' platform for the sheath. The following
fig 11 shows the different types of core arrangements.

Fig: 11 Types of Core Construction

10. Sheath Construction

The job of the sheath is to protect the core and against abrasion and it will largely
define the handling characteristics of the rope. The choice of how much material to
utilize and the style of sheath is made by referring back to the usage characteristics of the
rope. The overall performance of the sheath is optimized by the relative twist levels of the
sheath yams, the angle at which the sheath yams are laid, the number of sheath yams
chosen and the configuration of the braid. A braid can be explained as the process of
configuring the sheath yams around the core it defines the sheath pattern and will
influence the handling and durability of the rope.

11. Innovative Braid Technology [11].

In general, the tubular braiding process consists of intertwining two systems of

yams alternately passing over and under each other in the bias direction, causing a zigzag
pattern on the braid surface. One system of yams moves helically clockwise with respect
to the fabric axis while the other moves helically counter-clockwise. The resulting
braided fabric is a tubular structure. When a tension load exerted in the axial direction
extends a braided fabric, the reinforcing yams are uniformly loaded with all of the
continuous yams within the braid. A redistribution of this load occurs because geometric
stress concentrations or minute differences in yam length and cause uneven yam loading.
In this scenario the most highly loaded yam straightens and thereby induces crimp in the
neighboring yams. The additional crimp then introduces increased load in the
neighboring yam. This self-correction process continues until all yam loads within the
braid are equivalent. For this reason a braided structure yields only when all yams yield
simultaneously. This unique feature of braid, often described as a "Chinese handcuff,"

Indian Institute of Technology, Delhi 12 2008TTE2881

Department of Textile technology
 “Braiding”

This unique feature of braid, often described as a "Chinese handcuff," is integral to the
inflatable tubular air bag applications. When a biaxial braid is inflated internally, it
expands in diameter and shrinks in length. The rate of length reduction increases as the
braid expands beyond its nominal diameter, which occurs at a braid angle of ±45˚ as
shown in Figure 12. The rate of braid angle change increases more significantly at these
larger diameters. The stowed length of the tubular air bag is considerably longer than the
deployed length. Upon inflation, the internal pressure causes the air bag to expand to a
known diameter and decrease in length to form a taut structure between anchor points
within a vehicle. This shortening function, which significantly contracts in length while
increasing in diameter as internal pressure is realized, is shown in Figure 13. During the
inflation, axial tension force is developed due to the fixed endpoints preventing the braid
from contracting freely. Since the stowed length in all applications is longer than the
deployed length, the ratio of deployed length, Li, to stowed length, Lo, is one of the most
critical functional parameters and is called the slack ratio.

Fig: 12 Braids Functional Architecture

Fig: 13 Function of Tubular Braid-Principle of Operation

Indian Institute of Technology, Delhi 13 2008TTE2881

Department of Textile technology
 “Braiding”

12. High Elastic Materials [12]

Braided textile structures do not rely on a matrix to transmit load to the fibers, as
in textile composites. Instead, yams within a braid are able to change orientation quite
freely under increasing tension until the "locking angle" is reached as shown in figure 14
at which point the structure exhibits a rapid increase in stiffness. Previous composite
models, which rely heavily on a fixed fiber orientation and volume fraction for predicting
mechanical properties, are therefore not valid for braided textile structures where
deformations can be large, causing significant changes in textile architecture. Existing
models of rope and braided structures generally assume that the structure does not change
appreciably during loading which is only appropriate for structures undergoing small
strains.

Fig 14 Yarn cross-sections before (top) and after the locking angle is reached

A plot of the load vs. extension in a braided rope shows an initial zero load
plateaus and then a dramatic increase in load, the onset of locking as shown in fig 15.
This difference is caused by a consolidation of the fibers within the strand, resulting in an
increased resistance to further rotation and compaction. The factors influencing the point
at which locking occurs are many, including the level of twist in the yam, yam size,
number of yams or carriers, coverage, braid angle, braid type, mandrel diameter, and
constituent properties. As one would expect, locking occurs sooner in braids with larger
strand widths and coverage. However, because of the combination of parameter values,
smaller initial strand spacing equates to a larger degree of shear deformation prior to
locking.

Fig 15 Load - extension curve of braid

Indian Institute of Technology, Delhi 14 2008TTE2881

Department of Textile technology
 “Braiding”

13. Important Braid Relationships

Fig: 16 Braided Tube heights H Fig: 17 Braid Geometry of Helically Slit Tube
(Braided diameter db) of One Pitch Length
(L-is the helical length, α/2 =braid angle)

Fig: 18 Unit-Cell Geometry to Determine Cover Factor;

(x and y are unit-cell height and width, respectively)

Brunnschweiler [4] has derived certain equations based on certain constants, by

considering a trellis unit as shown in Figure 18. The axes of two adjacent strands form a
trellis unit with the axis passing through points CA in the figure denoting a trellis unit
ABCD.
M = Wz / (4*m* nb) grams, -------------------------------- --(1)

Where M (g) = mass of thread forming one side of the trellis unit
Wz = mass of plaits of a braid in grams
m = number of strands forming the braid
nb = number of threads per strand.

Further, M = Kb 1 x 105 ------------------------------------------------------ (2)

Where, Kb (Tex) = count of the yam in the strand

1 (cm) = the average length of thread forming one side of trellis.

Indian Institute of Technology, Delhi 15 2008TTE2881

Department of Textile technology
 “Braiding”

And 1 = (W X 105) / ( 4*m* nb * Kb) ---------------------------------- (3)

The strand width and the number of carriers determine braid angle for given part
perimeter in accordance with the mathematical relationship.

Sin (α/2) = [Wy m] / [2 P], --------------------------------------------- (4)

Where, α/2 = Braid angle

Wy = Strand width, & P = part perimeter.

Some variations can be obtained by varying the yam feed rate. Increasing the yam
feed rate up to the point where an open braid is formed can decrease braid angle. Yam
feed rate and braider speed are dependent on the shape and size of the mandrel to be
covered By means of theoretical and geometrical method, weber-partenheimer, as
referred by Turner [8], produced rules to, calculate the braided cord diameter (db)from the
strand width for a certain number of carriers as

[ db / wy] = (m+3)/3 --------------------------------------------------- (5)

Zhang et al [9] developed following equations by bias slitting of one pitch of

braided fabric to produce a flat fabric of helical length (L) and width (W).

L = db / Sin (α/2) ------------------------------------------------------ (6)

W = Π db Cos (α/2) --------------------------------------------------- (7)

Ko [10] developed certain equations to determine the diameter of the braid for
braided composites as,

dbo = ( m ×nb×Ay /{ Π b× T× Vf × cos(α /2) } + T

db = (m× nb ×A") /{ Π× T× Vf × cos(α /2)} -T,

Where, dbo and db; represent the outside and inside diameter of the composite
respectively,

T is the thickness of the braid and

Vf is the fibre volume fraction.

Indian Institute of Technology, Delhi 16 2008TTE2881

Department of Textile technology
 “Braiding”

14. Effect of braiding parameter on braid properties and structure [7]

i) The change in braid formation point from maximum height (20 cm) to
minimum height (6 cm) with respect to spindle top result in significant
increase in braid angle and decrease in load bearing capacity (in the case of
2/2 regular braid).
ii) The increase in spring tension from 200 gf to 650 gf, keeping the other
parameter as constant results in increased braid angle, which substantially
lower the braid load bearing capacity and it’s translational efficiency.
iii) To increase in take-up roller speed from 0.58 m/min to 33.5 m/min, keeping
other parameters as constant results in decreased braid angle, which
substantially increases the braid load bearing capacity and it’s strength
translational capacity.
iv) The increase in number of plies from 2 to 6 increase the mean tenacity, strain
and improvement in tenacity and strain c.v % in the respective plied yarn.
v) The twisted cords gives higher load bearing capacity and strength translational
efficiency than braided core made from equal number of thread.
vi) The experimental study on structural and mechanical property between core
braid (50:50 ratio) and hollow braids with similar interlacement pattern using
6 ply cotton yarn as a feed material shows higher tenacity in core braids.

Indian Institute of Technology, Delhi 17 2008TTE2881

Department of Textile technology
 “Braiding”

15. References:

1. Adanur sabit; 1995, “willingtone sears hand book of industrial textiles”; pp 133-
135.
2. Brunnschweiter, 1953. “Braiding & Braids”, journal of textile institute, vol. 44,
pp 519-528
3. Jarmila sivevora, 1990, “textile science & technology”, industrial textiles, pp 339-
346
4. Brunnschweiter, 1954. “Braiding & Braids”, silk & rayon record, vol. 28, pp 254-
257
5. D. bigand et al, Model of interaction between process,microstructure and
mechanical properties of the composite material- a study of the interlock layer to
layer techniques, composite structure 67(2005) 99-114
6. T. Ganesan, “Development of mechanism for triaxial over-braided performs of
wrapped glass yarn & their composite”, 2006, project work.
7. Sunay omeroglu “The effect of braiding parameters on the mechanical properties
of braided ropes” fibre & textile in Europe , October / December 2006,vol 14, no.
4(58)
8. Turner, 1976, “The production and properties of narrow fabric braiding”, textile
progress, vol. 88, pp 45-52\
9. Zhang, Q. Beale, D. Adanur, S. Broughton, R.M & Walker, R.P. 1997. “Structural
analysis of two dimensional braided fabric”, journal of textile institute, vol. 88,
part-I, No-1, pp 41-52
10. Ko,K. Frank, 1987, “Braiding”, engineered material hand book, composite, vol. 1,
pp 519-528
11. Greg mowing, Andrew head, “braided inflatable tubular structural technology in
crash safety” journal o industrial textile, vol. 30, No-3, January 2001
12. Julie Chen, Armand lewis, Stevors B, Warner. , stress elastic material- national
textile centre research briefs: June 2000

Indian Institute of Technology, Delhi 18 2008TTE2881

Department of Textile technology