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Indian Journal of Fibre & Textile Research Vol. 22, December 1997, pp. 360-368 Textile rope -A review R Chattopadhyay Department of Textile Technology, Indian Institute of Technology, New Delhi 110016, India Natural and synthetic fibre ropes have been discussed in tenns of their properties, behavioural characteristics and applications. A comparative assessment of the attributes of the fibres used in ropes has also been made. Keywords: Cord, Rope, Twine 1 Introduction Rope has been in use for a long time and has played an useful role In the progress of civilization. It has an unique property of resisting large axial load in comparison to bending and torsional load. A variety of natural fibres has been used as a basic element in rope construction for centuries. Today, with the advent of synthetic fibres, the field of application has widened with associated improvement in performance. With the progress in manufacturing technology, newer constructions are being made with improved performance. As a result, a variety of rope now finds its way in household, industrial, civil construction and defence sectors for performing a va rIety of ta sk. Textile fibre rope has advantages over its metallic counterpart for a number of reasons (Table 1) and it is increasingly being preferred in many applications over metallic ropes. 2 Fibres for Rope Both natural and synthetic fibres are used in rope. Synthetic fibres can be used either in staple or continuous filament form. Some typical values of fineness, extension at break and tenacity of most commonly used fibres are given in Table 2. The man-made fibres used for rope can also be classified according to the performance level attained by the rope made out of them as follows I: Adequate perfo rmance : Polyolefins-ordinary grade polyethylene and polypropylene. fl1lerll1 ediate peljormance : Strong polypropy- lene fibres, polyamides (nylon 6 & nylon 66), polyester and glass. High jJerformance para-aramids (Kevlar, Twaron. Technora, etc.), high modulus polyethylene (Spectra, Dyneema) and liquid crystal aromatic polyester (vectran carbon). Table I-Comparison between textile and metallic ropes Textile rope Fibre ropes are stronger when compared on the basis of weight Man-made fibre rope has a hi gh energy absorption capacity It is susceptib J,e to creep Fibre rope is not clastic. A hysteresis loop is observed during cyclic ioading, indicating lo ss of energy. This cnergy is absorbed by the system and results in heating. If load is large and ti'equency is hi gh, it may lead to fusion . Fibre ropes are more sensitive to mechanical damage Fibrc ropes do not deteriorate in water i.e. they have no rll st in g problem. Th ey may be selectively degraded by some chemicals dissolved in water Fibre ropes are affected by UV radiation Heatln, ' generally progressively reduces strength Metallic/ wire rope Metallic ropes are stronger when compared on the basis of size It is poor for wire rope They do not creep Wire rope does not show hysteresis Wire ropes are less sensitive These ropes are susceptible to rust formation \\- Ir e ropes have no effect Heat influence only when the temparature is very high
Transcript

Indian Journal of Fibre & Textile Research Vol. 22, December 1997, pp. 360-368

Textile rope -A review

R Chattopadhyay

Department of Textile Technology, Indian Institute of Technology, New Delhi 110016, India

Natural and synthetic fibre ropes have been discussed in tenns of their properties, behavioural characteristics and applications. A comparative assessment of the attributes of the fibres used in ropes has also been made.

Keywords: Cord, Rope, Twine

1 Introduction Rope has been in use for a long time and has

played an useful role In the progress of civilization. It has an unique property of resisting large axial load in comparison to bending and torsional load. A variety of natural fibres has been used as a basic element in rope construction for centuries. Today, with the advent of synthetic fibres, the field of application has widened with associated improvement in performance. With the progress in manufacturing technology, newer constructions are being made with improved performance. As a result, a variety of rope now finds its way in household, industrial , civil construction and defence sectors for performing a varIety of task. Textile fibre rope has advantages over its metallic counterpart for a number of reasons (Table 1) and it is increasingly being preferred in many applications over metallic ropes.

2 Fibres for Rope Both natural and synthetic fibres are used in

rope. Synthetic fibres can be used either in staple or continuous filament form . Some typical values of fineness , extension at break and tenacity of most commonly used fibres are given in Table 2.

The man-made fibres used for rope can also be classified according to the performance level attained by the rope made out of them as follows I:

Adequate p erformance : Polyolefins-ordinary grade polyethylene and polypropylene.

fl1lerll1 ediate peljormance : Strong polypropy­lene fibres , polyamides (nylon 6 & nylon 66), polyester and glass.

High jJerformance para-aramids (Kevlar, Twaron. Technora, etc.), high modulus polyethylene (Spectra, Dyneema) and liquid crystal aromatic polyester (vectran carbon).

Table I-Comparison between textile and metallic ropes

Textile rope

Fibre ropes are stronger when compared on the basis of weight

Man-made fib re rope has a high energy absorption capac ity It is susceptib J,e to creep Fibre rope is not clastic. A hysteresis loop is observed during

cyclic ioading, indicating loss of energy. This cnergy is absorbed by the system and results in heating. If load is large and ti'equency is high, it may lead to fusion .

Fibre ropes are more sensitive to mechanical damage Fibrc ropes do not deteriorate in water i.e. they have no

rll st ing problem. They may be selectively degraded by some chemicals di ssolved in water

Fibre ropes are affected by UV radiation Heatln, ' generally progressi vely reduces strength

Metallic/ wire rope

Metallic ropes are stronger when compared on the basis of size

It is poor for wire rope They do not creep Wire rope does not show hysteresis

Wire ropes are less sensitive These ropes are susceptible to rust formation

\\- Ire ropes have no effect Heat influence only when the temparature is very high

CHA TfOPADHY A Y: TEXTILE ROPE 361

Some attributes of synthetic and natural fibres which ' influence rope perfonnance and properties are given in Table 3.

Polyester rope-Suitable for mooring application for ship and buoy, hauling, lifting, cable recovery, supporting antenna, etc.

The attributes stated in Table 3 make the ropes made out of these fibres especially suitable for certain end uses / application as stated below.

Polypropylene rope-Suitable for those application where the rope is demanded to remain in floating condition in water.

Nylon rope-Suitable for climbing since it gives adequate protection from fall due to high energy absorption capacity and less peak load to be experienced by the body. Good for accommodating high amplitude motion in mooring.

Kevlar rope-It's high modulus facilitates anchoring floating oil platfonn in sea in place. It can be used as a replacement of wire rope in suspension bridge.

3 Rope Constituents

Table 2-Properties of fibres used in rope

A rope is made of several strands twisted, plaited or braided together to fonn a coherent assembly. The strands are made of yams which consist of fibres, filaments or tapes. The constituents in an hiarchial order are shown 10 Fig.l . The nomenclature used to describe certain one dimensional linear structures is given below:

Fibre

Cotton Flax Jute Abaca Sisal Henequen Coir

Synthetic Polyethylene Polypropylene Polyester Nylon Kevlar (Ararnid)

Fibre

Polyamide

Polyester

Polypropylene

Kevlar

Natural fibres

Fineness dtex

1.5 2.2

15-27 139-273 206-406 362-383 180-540

>5

Extension Tenacity % cN/dtex

8 3.6 1.6 5.9 1.5 3.0 2.8 5.8 2.9 4.7 2.7 42 1.2

Tnti .. yom

Rope JOI'fti , ... "'''"% _RI ..... Rop.

20 3 >5 20 3 >6 15 8 ~.............-.----z- TWlst.d >6 <2

20 8.5 <5 20 Fig. I-Rope constituents2

Table 3--Attributes of synthetic and natural fibres

Positive attribute Negative attribute

High extension, elastic, flexible, high energy absorption capacity, good abrasion resistance in dry state, little diameter ratio restriction while working on sleeves or pulleys

Strong, elongation less than nylon, wet abrasion resistance and fatigue behaviour better than nylon Cheaper than nylon and polyester, density less than water, soft in handle

High strength to weight ratio, high modulus, extension less than nylon and polyester but more than steel wire, remains unaffected by conventional corrosion in ocean, low creep, non conductivity Biodegradable, cheap

Poor abrasion resistance in wet condition, swelling in water results in strength loss by 10-20%, very high extensibility under large load in the case of twisted structure, possibilities of kink formation after a sudden retraction.

30% weaker than nylon and polyester, poor fatigue resistance, degrades in sun Iight,poor creep behaviour, necessitates larger and heavier rope for similar application Extension less than nylon and polyester, poor compressive properties, poor abrasion resistance, low damage tolerance

Not durable, weaker than their synthetic counterparts, absorbs water , poor mildew resistance

362 INDIAN 1. FIBRE TEXT. RES., DECEMBER 1997

Twine-It is an assembly of twisted yarns or tapes used for tying or binding.

Rope-Any article of cordage more than 4 mm in diameter obtained when (a) three or more strands are laid or plaited together or (b) a core is covered by a braided or plastic film sheath.

Cord-A term applied to a variety of textile strands including (a) cabled yams, (b) plied yams, and (c) structures made by braiding, knitting or weaving. Diameter wise they are generally less than lOmm.

4 Rope Classification Ropes can be classified according to the

construction, raw material or application areas. Based on construction, ropes can be twistedllaid, braided/plaited, wire rope type, parallel or pultruded. Within a particular construction, a lot of derivatives are possible glvmg innumerable constructions to suit specific end uses. A simple description of the different varieties is given in Table 4 and some typical constructions are shown in Fig. 2.

Besides the above-mentioned basic constructions , several hybrid constructions are also possible such as

• Several low-twisted rope yams encased in braided jacket.

• Rope blends or combination rope structures such as

Rope blend

Strand blend

Rope yam blend

Filament blend

Fibre metal blend

Sheath (i.e. cover) and core differ in material type and form Rope strands differ in type and form Constituent yams or filament differ in type and form The polymer is either copolymer or blend of homo polymer Core may consists of strand made from steel and the outer sheath is made of fibrous material

5 Behavioural Characteristics Every construction gives specific behavioural

characteristics (Table 5) from which the suitability of a construction for an application can be assessed.

Twisted ~ . ., .~ -- - ---..~

Plaited '"

Braided .. e

Parallel .. ' 111".:~.=:: _. .. .. , . ,_ .....• .' .:. ' ;~~AE..

. . 1IJa,.. ....... ~ ~ .....---

Pultruded

Fig. 2- DitTerent rope constructions '"

6 Properties of Rope

6.1 Strength Tensile strength is the most desirable property in

a rope since it has a strong association with durability. The strength of a rope mainly depends upon raw material, construction and test environment.

6.1.1 Influence of Raw Material The strength primarily depends upon the strength

of its constituent fibres. Stronger fibre would result in a stronger rope. The strengths of typical 8-strand plaited ropes of 64 mm diameter are given be1ow6

:

Fibre Strength (tons) Sisal 25.7 Manila 32.0 Polypropylene 46.6 Polyester 57.9 Nylon 72.0

Synthetic fibre ropes are stronger as compared to natural fibre ropes because of their strong constituent fibres.

CHA TTOPADHY A Y: TEXTILE ROPE

Table 4-Types of Rope and constructional features

Description of structure Type of rope

TwistedlLaid 3-strand hawser laid

4-strand shroud laid

Cable laid

Spring laid

Hard laid

Soft laid

BraidedlPlaited Squareline

Normal

Hollow

Core

Double braid

Solid braid

Twill braid

Parallel Parafil

Superline

Pultruded

Wire rope

Three strands are twisted together to form helices around the same central axis

Ropes of four strand with or without core with strands twisted to form helix

Three or more ropes are laid around the central axis

A rope made of six strands around a main core. Each strand has alternating wire and fibre component laid over a fibre core

A rope with length of lay of strand and/or rope shorter than usual

A rope with length of lay of strand and/or rope longer than usual

It consists of 8 strands. Four of them are twisted in Z direction and the rest in S direction. The strands are plaited together in pairs

One strand of one direction of rotation about the axis of the rope passes over other in opposite direction

Plain or twill braided construction with empty centre

Hollow braid with centre filled with yams

Two hollow braided one inside the other.

Each strand alternately passes under and over one or more of the other strands, while all strands rotate around the axis with the same direction of rotation. On surface all strands appear to be parallel to rope axis

One strand of one direction of rotation about the axis passes over two strands of the opposite direction and, in tum, passes under the next two strands of opposite direction

Filaments after being bunched parallel are enclosed within an extruded polythene or polyester sheath

Instead of filaments, rope yams or small diameter ropes can also be encapsulated in a protective cover. Half of the rope yams are S twisted and the other half Z twisted.

Number of filaments are bonded together by a matrix in composite carbon, glass and Kevlar fibres and then encased in

It consists of several strands,arranged in a regularly layered structure i.e. one in core surrounded by six outside strands helically wrapping the core or successive layers containing one, six, twelve and eighteen strands

363

364

Construction

Twisted

Braided

Parallel/parafil

Pultruded

6.1.2 Influence of Construction

INDIAN 1. FIBRE TEXT. RES., DECEMBER 1997

Positive

Table 5-Behavioural characteristics

Negative

It has higher energy absorption capacity because of its high elongation potential

It can bend easily

It is suitable for discontinuous fibres i.e. all natural and staple cut fibres

It results in high level torsional stability

Highly flexible

It does not develop torsional stresS at all

The constituent filaments can contribute fully towards sharing of tensile load, hence in­creases strength translational efficiency

The structure results in high tensile modulus and low stretch

Strong and rigid

High abrasion resistance

Shows tendency to rotate on its axis during loading. Therefore, torque-free construction under wide load application is difficult

The transverse forc(:s between the strands at the interfacial contact point become a source of friction leading to damage

Elongation less than that of twisted structure

Braided structure is inferior to twisted structure in flexing endurance

Due to lack of mutual support between filaments, variability has a great effect on strength

The parallel configuration of filaments make the structure more rigid i.e. it does not bend easily

High bending stiffness

Construction plays a very useful role in deciding the properties of rope. Tenacity values of some typical polyester rope constructions are given below7

:

the strands can contribute fuHy to the sharing of load. As the twist adversely affects strength, a tightly-twisted hard-laid rope will be weaker than the corresponding norrnallaid rope.

Type of rope construction 3-strand laid 8-strand plaited Circular braided Wire rope construction Parallel rope Parallel yam

Tenacity (glden) 2.0 2.4 2.6 3.5 3.8 4.2

The 3-strand laid rope shows lowest strength due to presence of large twist used in making the rope. The braided construction improves strength with respect to 3-strand due to presence of less twist in the structure. Parallel arrangement of strands or filaments in core produces the strongest rope, since

6.1.3 Influence of Heat

In many situation, ropes may be needed to be used in a heated environment. Therefore, influence of heat on strength will be an important criterion for

, their selection. Heat has a pronounced effect on the strength of rope because it either causes fibre imbrittlement or softening of the polymer. The effect of temperature on breaking strength of some ropes is shown in Fig.3.

Natural fibre ropes lose strength progressively as the temperature rises and so do the polypropylene and polyethylene fibre ropes. Nylon and polyester fibre ropes do not lose strength till 140°C, but beyond that an abrupt failure occurs.

CHA TTOPADHY A Y: TEXTILE ROPE 365

56r-----------------------, 1------------Ny Ion

48

~--------~P~O~Iy.S~

40 z .lI:

" :J: ~ 1=:1 Z UJ a: ~ ~

1=:1 Z ::.::: < IoU a: co

.Fig. 3-Effect of temperature on rope strength6

Table 6---Influence of wetting on fibre and rope strength5

Fibre type in Effect of wetting Measured rope rope on fibre strength strength ratio (wet! dry)

Manila Gain 0.97-1.10 Sisal Gain 0.90-1.13 Jute Loss 0.90-0.98 Cotton Gain 1.04-1.35 Nylon Loss 0.77-1.00

6.1.4 Influence of Wetting

Wetting has an important effect on the structure and properties of rope depending upon the raw material used (Table 6) ..

The fibres which absorb moisture and swell leading to shrinking in length of the rope, cause the angle of twist to increase and hence the hardness. This is expected to reduce the strength when wet since the constituent yams get locked into the structure without getting an opportunity to align themselves along the direction of application of load. Hence, they contribute less towards load sharing. Strength may increase in some cases, especially for those fibres which show an increase in strength due to wetting.

'·0....-------------------,

~

~ >-~ '-' z 0.8

~ w c; . ..: u. w z

0. 6 ~;:~~ Q I- : : :3 ~:; ; ~ ::: VI

~::::::: : : z <{ a:: I- 0.4 l>. Polypropylene (fibrillatrd) :r v Polypropylene (Mament) I-

"" o Polydhylen~ z w o Polyaml de a:: I- 0 . 2 x. Polyester VI

• Sisal / manil.a (3 strand) A Sisal / manila (4 strand I • S I sal / manila (9 strand I

20 100 120 140 '60

ROPE DIAMETER, mm

Fig. 4-Strength translation efficiency of ropes

6.2 Strength Translation Efficiency The strength of a yam is generally less than the

algebraic summation of strength of constituent fibres across the yam cross-section. This is generally ascribed to obliquity effect in the case of twisted structures and variability in breaking extension of constituent fibres. Same is the situation in the case of rope i.e. strength translation from fibre to rope is never 100 % . The strength translation efficiency (STE) or realization factor of some typical ropes is shown in Fig. 4. The realization factor reduces with increase in rope diameter.

The STE value for polypropylene is highest followed by polyethylene, polyamide and polyester. These differences can be attributed to the modulus differences of the constituent fibres. Polypropylene having the lowest modulus can easily yield and adjust itself within the structure when stress acts on it. As a result, it can easily orient itself towards the direction of application of load and, therefore, can share the load more uniformly. A stiff fibre will not be able to adjust itself so easily within the structure and will remain in distorted configuration. As a result, when the rope is extended the constituent filaments/strands will asymmetrically support the load and fail early, leading to reduced realization.

6.3 Elongation Elongation reflects the ability of a rope to extend

under application of load. Whether such extension is desirable or not depends upon the end use. Elongation mainly depends upon (i) elongation of

366 INDIAN 1. FIBRE TEXT. RES., DECEMBER 1997

constituent fibres, and (ii) structural parameters such as twist and size. Elongation of some ropes along with their corresponding constituent fibres is given in Table 7. It may be seen that ultimate elongation of rope depends very much on fibre breaking extension. In wet state, rope breaking extension is more than that in dry state. Natural fibre rope shrinks in wet state, causing higher elongation at break.

Small size ropes generally show less extension. This is so because for same compactness, the strands in smaller size rope will remain less inclined with respect to rope axis than that of larger size rope. Hence, part of the total elongation that results from geometric consideration of fibre path would be more for larger size rope.

With hard laid rope i.e. rope having higher twist, the elongation of the rope would be more due to same geometrical consideration.

Rope elongation also depends upon preload level used for eradicating constructional looseness. Whenever a rope is loaded, a part of the total elongation becomes permanent. The magnitude of this permanent elongation would depend upon preload level. The more the preload the less would be the elongation to break.

Rope elongation also gets affected by service condition and weathering. If it leads to constructional looseness, the rope will show higher breaking extension which will be mainly manifested in the initial region of load-elongation curve.

6.4 Load-Elongation Behaviour The load-elongation diagram of a rope reveals

useful information about a rope. Fig.S shows the stress-strain diagram of a fibre, corresponding rope yam and braided structure8

• There is not much difference between the fibre and the corresponding yam till a reasonable load level in the initial region of the cwve. However, the braid made out of it shows a significant different character. The curves for ropes get very much inclined towards strain axis indicating that when these fibres are converted into rope, similar specific tension level causes the rope to yield much more than the fibre, emphasizing the role of structure (i.e. spatial arrangement of fibres) on tensile behaviour.

Fig. 6 shows the load-elongation behaviour of twisted 64 mm diam. polyester and nylon ropes.

Table 7-EJongation of different fibres and their ropes with 32 mm circumference in dry and wet conditionss

Fibre type

Manila Sisal Jute Cotton 'Nylon

1.0

)(

GI 0.8 -z

z 0.6 0 Vi z UJ .- 0·4 LJ

u.. LJ 0.2 UJ n. Vl

Fibre breaking extension Rope breaking

Dry

2.8 2.9 \.5 7.4 12.0

%

Wet

3.2 3.4 \,4

8.1 14.0

Fibre

Yarn

Light Rope

extension,%

Dry

13.0 13 .0 i3.3 17.0 39.0

/ ,

Wet

15.0 16.0

3 \.0 40.0

, Break

,," Heavy Rope

0.4

STRAIN, .,.

0.5

Fig. 5-StresS-strain diagram of fibre, yam and braided ropes

90 .r-------;;-:-;;:--;-------------.

.,. ..

80

70

.. 50

.., 40 o o

..... ]0

20

10

j Strand 8 Strand nylon

,. ... / /

O .~~~~~~~~~~~-~~~ 5 10 15 20 25 ]0 35 40 4S 50 SS 60 6S 70 7S

EXTENSION, 'I.

Fig. 6--Load-elongation behaviour of ropes6

Braid line is stiffest than equivalent 3- or 8- strand nylon rope due to parallel arrangement of core fibres. Generally, the load elongation curves are concave i.e. inclined towards extension axis. Polyester rope is less inclined than nylon since polyester fibres have higher modulus than nylon fibres.

Fig. 7 shows the load-elongation diagram for steel, Kevlar, polyester and nylon ropes. Kevlar

CHA TIOP ADHY A Y: TEXTILE ROPE .367

shows a similar behaviour like steel, pointing possibility of replacing steel wire rope by a lighter Kevlar rope. Nylon ropes are most extensible and with plaited construction the curve is closest to the extension axis, implying easy extensibility under low load.

6.5 Rope Recovery from Stretch

When an applied load is removed the rope starts recovering from the extended state, part of the recovery being almost instantaneous, whereas the rest proceeds progressively with time, with a part remaining unrecovered permanently. The amount of recovery depends upon magnitude of appl;ed load, size of rope, structure and nature of rope material.

More than half of the total recovery takes place within minutes and the rest, though continues slowly, becomes practically insignificant beyond 1000 h with a permanent elongation left unre~overed5 .

The recovery is more if the load applied is less and the smaller size rope recovers more readily than the larger size rope. A rope made of elastic fibre like nylon or polyester is expected to recover more than natural fibre rope. With respect to structure and size it can be stated that a structure or size that leaves the possibilities of more readjustment of individual yams, strands or filaments within it, causes less recovery. As a result, a larger size rope or a 4-strand rope shows less recovery than a smaller size rope or 3-strand rope.

Repeated loading improves the recovery behaviour of rope since with repeated loading the structure gets compacted and starts . showing complete recovery provided the load applied does not exceed the load used to pre-stretch the rope.

6.6 Creep

Creep is the continued extension that a rope undergoes when it is under tension. Such a behaviour may have two consequences in actual use. In the first case, when a rope is used to secure tightly any object, the tautness will reduce slowly and the rope will become slack due to creep and accompanying stress relaxation. In the second case, if it is used to support a load, the continued extension may even lead to failure of the rope even though the load supported may be much less than the breaking load of the rope.

500.--------- ------------,

400 , Paroll,l yorn

(Kfvlar' :; 300

I I I ,

>-- , , ~ 200

Porolltl yarn ( Pelyft'.r' PatOn., ropt

(Poly" .... '

Parah' ropt tNylon' o

--'

100

30

EX TENSlnN , %

Fig. 7-Stress-strain diagram of steel, kevlar, polyester and nylon· ropes7

Creep depends upon the ultimate elongation of the fibre, type of rope structure, size and the magnitude of applied load. It has been reported5 that manila rope fails faster than cotton rope 'under comparable load and the difference becomes too obvious at lower working load. As an example at an working load of 78% of breaking strength, the cotton and manila ropes break in 1.4 and 1.2 h respectively, whereas at 60% working load, they break in 481 and 12 h respectively. Creep test conducted on 6 mm polypropylene and nylon shows that nylon rope creeps less than polypropylene, though overall extension of nylon rope is much higher due to the high level of instaritaneous extension for nylon (Table 8). While assessing the role' of structure it has been found that though twisted rope results in more total elongation than braided rope, the creep is actually higher for braided structure. In another study'O on parafil ropes, Kevlar showed its superiority over polyester (Table 9).

6.7 Flexing Endurance When a rope moves over a pulley it gets

repeatedly flexed. As a result of flexing the strands roll one over another in the part where it contracts (inner part of the curvature) and are pulled away from each other at the outer part of the bend. The fibres are, therefore, subjected to repeated flexing, compression, tensile and abrasive actions. Flexing endurance becomes an important property in such application.

In the case of twisted rope, flexing endurance improves with twist and an SSZ construction has better flexing properties than the ZSZ constructions. Between braided and twisted structures; the twisted structure is superior than the equivalent braided

368 £NOlAN 1. FIBRE TEXT. RES., DECEMBER 1997

Table S----Influence of fibre type and construction on creep behaviour of rope9

Type of rope Rope size Instantaneous extension Time dependent extension Total extension

Polypropylene Nylon Twisted nylon Double braided nylon Single braided nylon

mm

6 6 6 4 4

%

5.7 20.6 17.0 7.4 7.0

% %

2.3 8.0 to 21.6 4.0 21.0 7.6 15.0 7.6 14.6

Table 9-Creep of parafil ropelO

Parafil rope Core yam Nominal breaking load Elastic modulus of fibre Core diameter Creep

Type A TypeB TypeC

Polyester Kevlar29 Kevlar 19

tons

20 22.5 22.5

Tirn~24 h; Load--40 % of nominal breaking load

structure of same size and material. Flexing endurance can be improved by impregnating the rope strand with lubricant as it reduces inter-strand and yam fiiction.

7 Conclusion Both natural and synthetic fibres are used in rope.

Five types of rope construction are commonly used, viz .. twisted, braided! plaited, parallel, pultruded and wire rope construction. The properties of rope are mostly influenced by the properties of raw material, structure and environment. Since there is no unique structure and raw material tmtt will be suitable for every application, the final selection of a rope for a given application should be based on judicious consideration of performance expected and the cost to be incurred.

References I Hearle J W S, Text Horizon, May (1996) 12-15: June-July

(1996) 28-31.

leN/mm2 mm %

9.8 24 0.41 77.7 15 0.09 126.5 15 0.04

2 Bacher S & Seo M, Mechanics of degradation of marine rope, in Objective measurement: Application to product design and process control (The Textile Machinery Society of Japan), 1985, 661 .

3 Tubbs M C & Danniels P N, Textile terms and definitions, 9th edn (Textile Institute, Manchester, UK).

4 David T, Jams A F, Paul R & Warren F K, Aramid structure-property relationships and their role in application development, in Handbook of fibre science and technology: Vol Ill-High technology fibres, Pt-B, edited by M Lewin and J Preston (Marcd Dekker Inc., New York), 1989,35-82.

5 Himmelfarb D, The technology of cordage fibres rfJpe, [Leonard Hill (Books) Ltd, London] 1957.

6 Yeardley J K & Dunn B J, Ropes for the offshore oil industry, Proceedings, Conference on Textiles in Oil Industry, (Shirley Institute), 1977, 87- 108.

7 Text Horizon, May (1986) 22-24. 8 Backer S, Yams, cords and ropes, in Proc.,Mechanics of

Flexible Fibre Assemblies, edited by ] W S Hearle, J J Thwaites & J Amirbayal, (NATO Advanced Study Institute), 1979, 535-542.

9 Thombre P E, An investigation on the mechanical properties of industrial rope, M Tech thesis, Indian Institute of Technology, Delhi, 1990.

10 Martin P, Text TechnolInt, (1996) l70-ln.


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