Indian Journal of Textile ResearchVol. 8, December 1983, pp.105-110

Influence of Yarn and Fabric Properties on Tearing Strength of Woven Fabrics

I C SHARMA, SUDEEP MALU, PANKAJ BHOWAN & SURENDER CHANDNA

The Technological Institute of Textiles, Bhiwani 125022

Received 28 May 1983; accepted I December 1983

The effect of different yarn and fabric parameters on the tearing strength of fabrics having plain, 2/2 twill, 3/1 twill and 4­thread satin weaves and woven using 52' reed and 2/40' polyester-viscose (15/85) warp has been studied. Weft count, weft twistmultiplier and pick level were varied in the plain woven fabrics. It was observed that with increase in yarn fineness, twistmultiplier and pick level, there is a decrease in tearing strength. The effect of yarn withdrawal force, crimp level elongation,weight/m2 and cover factor has also been studied. Increase in float length increases !earing strength, which is minimum in thecase of plain weave and maximum in the case of 4-thread satin.

Generally, tensile strength is taken as the criterion forpredicting the serviceability of a cloth. Taylordisagreed with this view and observed that in contrastto tensile strength, tearing strength is directly involvedin the assessment of serviceability. Tearing is muchmore a common mode of failure than fall in tensilestrength in actual wear. Tear strength indicates theability of a fabric structure to utilize the properties ofcomponent yarns. The results are dependent on thosevery factors which differentiate a fabric from itscomponent yarn, the geometry of woven fabric makingthe greatest contribution to the stress pattern. In otherwords, tear strength is more characteristic of thematerial in fabric form than in yarn form and cannotbe determined if any of the sets of threads, namelywarp and weft, is removed. Tear strength refers to aresponse to non-uniform tensile stresses, causing aprogressive tensile failure of cross yarns along a line,thread by thread or in small groups of threads.

Krook and Fox 1 studied the effect of fabric count

(both warp and weft ways) on the frequency of waves inthe chart and on the tear strength of fabrics. Theyobserved that increase in fabric count in the testdirection has little effect on tear strength; anyreduction in the number of yarns in the del resultingfrom the decreased del size is almost compensated byincrease in the number of threads/in. However, theysuggested that the strength of a fabric could beimproved through (i) decrease in fabric count, (ii)increase in yarn strength, (iii) use of smoother yarn,and (iv) use of open weave.

According to Millard 2 , the factors affecting the tearstrength are : (i) strength of yarn, (ii) smoothness ofyarn, (iii) number of thick places, and (iv) number ofyarn slubs. O'Brien and Weiner3 pointed out theadvantage of plying in that the use of two-fold yarnsgives higher tearing strength than that when single

yarns of the same equivalent count are used. He furtherstated that tear strength is directly proportional toyarn strength.

Morton and Turner4 observed that increase in thetwist factor of component threads increases the tearstrength of fabrics because of increase in threadstrength and decrease in yarn diameter, the latterallowing a greater degree of freedom to the yarn.Backer and Tanenhaus5 and O'Brien and Weiner3

showed that tear strength increases with increase inweave factor, which they defined as the number ofthreads per repeat divided by the number ofinterlacements in the same repeat. Taylor 7 introduceda similar factor in his theoretical treatment of ripstrength.

Materials and Methods

Thirteen samples were prepared from a 15/18polyester viscose blended yarn. Out of these, threesamples were of 2/325, 2/365 and 2/405 counts, three of3.1,3.4 and 3.7 twist multipliers (TM) and four of 2/365weft count with 3.1 TM but different weaves, viz. plain,2/2 twill, 3/1 twill and 4-thread satin. In the remainingthree samples, three different pick levels, viz. 44, 50and55, were chosen keeping the other three parametersconstant. The warp count of 2/405 and 3.4 TM waskept constant in all the cases.

Prior to testing, all the samples were conditioned in astandard atmosphere (RH, 65% and temp. 27 ± 2eC)for 48 hr. Standard test methods as per IndianStandard specifications6 were used to determine theyarn and fabric characteristics. For yarn testing, skeinsof 120 yd were prepared and the average count wastested on Knowle's balance. Yarn crimp values forwarp and weft were measured using a test length of 20cm on Eureka crimp tester, Type FY-07, applying 109tension. Single yarn strength and elongation at break

105

INDIAN J TEXT. RES., VOL. 8, DECEMBER 1983

were measured on Instron tensile tester. The cross­

head speed and the ratio between cross-head speed andchart speed were kept as 110 mm/min and 1.1:1respectively. Clamping length of 100mm was used andthe fun scale load was adjusted to 10 kg on Instrontensile tester.

The single rip test method was used for determiningthe tearing strength of the fabric. The rip test consistsin mak~ngan initial longitudinal cut part way down thecentre of a strip and then pulling apart the two tailsthus fdrmed, so that the tear proceeds through theuncut portion of the specimen. The testing machineused for this purpose may be an inertialess (CRE)machine or a pendulum type (CRn instrument.Various dimensions have been used by differentworkers. We have, however, accepted the ASTMspecifications as shown in Fig. 1.

In CRE/CR T machine, one tail of the specimenshould ,beclamped in the upper jaw and the other onein the lower jaw (Fig. 1b) in such a manner that the cutedge o~the tail is in a straight line joining the centres ofthe clamps, the two tails presenting opposite faces tothe operator. The autographic device attached to theinstrurv.ent indicates a succession of peak values oftensions corresponding to the successive rupture ofyarn in the course of tear.

Instron tensile tester was used for the single rip teartest. The cross-head speed and the ratio between CroSS­head speed and chart speed were kept as 100 mm/minand 2:1 respectively. Clamping length of 100 mm wasused and the full scale load was kept as 10 kg. Theaverage tear strength of each sample was found fromfive observations for each sample.

For determining the yarn withdrawal force, keepingparity with Taylor's experiment, a strip of fabric (5 inlong and 3 in wide) was taken. leaving 2 in from oneend of the longer sides to allow the specimen to begripped by the fabric jaws, and another 0.5 in for aclearance from the jaw line, a transverse cut was madeacross .the width of the specimen. The specimen wasthen rv.arked across its width at a distance of 1 in

from the transverse cut and all the crossing threads inthe remaining portion of the specimen were unravelled,so that the length of each of the freed longitudinalyarns from the marked line was 1.5 in, the rear end ofthe specimen in the fabric form being already grippedby a pair of fabric jaws. The yarn clamp, initially beingseparated from the jaws by a distance of 2 in, was thenmoved apart until the said yarn was completelywithdrawn from the strip; the force required to removethe yarn was recorded in the autographic device. Theaverage values for all the tests were calculated from 10observations made for both warp and weft directions.

Results and Discussion

Effect of weft count on tearing strength-The effectof weft count on tearing strength was studied for threeplain woven fabrics having weft counts 2/365, 2/325and 2/405 • Data on the tearing strength and count (Fig.2.)indicate that when the fabric is ruptured in the weftdirection, its tearing strength decreases with increase inweft count. This may be attributed to the strength ofthe thread, because with increase in the fineness of theyarn, the number of fibres in the cross-sectiondecreases and this contributes to lowering of thebreaking strength of the yarn. Thus, with increase incounts, a corresponding decrease in weft breakingstrength is observed and this ultimately results indecrease in the tearing strength of the fabric in weft­wise direction. The statistical relation derived for thisaction gives the value of correlation factor as 0.885,indicating that the observations made are true and theweft count is closely related to fabric tearing strength.The value of warp-wise tearing strength, on the otherhand, increases with increase in weft count, becausethe breaking strength of the weft in all the three cases isgreater than that of the warp due to the coarser weftcount having more number of fibres in its crass­section.

The above finding is in agreement with that ofTurners, who found that the higher single threadstrength, usually brought about by the use of coarser

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SHARMA et at.: INFLUENCE OF YARN & FABRIC PROPERTIES ON TEARING STRENGTH OF FABRICS

Fig. 3-Effect of weft twist multiplier on tearing strength (0-0-0)and elongation (0 ... 0... 0)

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WEAVE - PLAIN

WEFT COUNTS - 2/32' ,2/36' ,2/4cT7'2 .

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Fig. 4-Relationship between weft elongation and tearing strength

6'4

the yarn (Fig. 3) and this results in decrease in thethread breaking strength. As observed earlier, increasein the thread breaking strength increases the fabrictearing strength and consequently decrease in thethread breaking strength (with increase in TM) causesa corresponding decrease in the tearing strength of thefabric.

Secondly, increase in TM decreases the area ofcross-section of the yarn and thus increases the yarn­to-fabric friction. Due to this, the force needed for thewithdrawal of yarn from the fabric is increased and thisresults in decrease in the tearing strength of the fabric.

Considering all the facts, it may be concluded thatdecrease in tearing strength (with increase in TM) isdue to decrease in elongation and yarn breakingstrength and increase in the yarn-to-fabric friction.Fig. 3 shows a close relationship between TM andtearing strength with the value of coefficient ofcorrelation as - 0.842.

Effect of yarn extensibility-Yarn extensibility playsan important role in determining the tear behaviour ofa fabric. The number of yarns in the ladder of a del atthe tear locus depends upon the extent of yarnextension. With increase in elongation of the yarn, theactive number of threads in del increases and hence

contributes more to the system in supporting a higherload. To better understand the matter, we focus ourattention on Fig. 4 to mark out three values of wefttearing strength for three different weft counts, viz.2/325, 2/365 and 2/405, while warp count is constant(2/405). The values of tearing strength are 7.29, 7.16and 6.56 kg for weft elongation of 40,37 and 34 mmrespectively. In the first case, the weft thread count was2/325, which led to higher extensibility of weft threads.Consequently, the number of threads in del increasedand hence contributed more to the system insupporting the higher load. In the second case, wherethe weft count was increased to the level of 2/365 , the

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yarn, causes increase in tearing strength. He alsopointed out that even a slight increase in coarsenessmight produce a large increase in the rip test, becausethe breakage occurs thread by thread in this test.

Increase in the coarseness of the weft count increases

the tearing strength of the fabric in the warp-wisedirection, because the thread breaking strength of theweft is comparatively higher than that of the warp dueto the greater number of fibres in weft cross-section,whereas increase in weft count decreases the tearingstrength of the fabric in the weft-wise direction due tothe decrease in the number of fibres in weft cross­section.

It is observed from Fig. 2 that with increase in weftcount, weft elongation decreases and this relationshipis linear. Also, the relationship is statisticallysignificant, having the value of coefficient ofcorrelation (r) as 0.81. The effect of weft TM on theelongation of the threads is shown in Fig. 3. It isobserved that with increase in weft TM, weftelongation decreases. The values of weft elongation are38, 37 and 36 mm for weft TM of 3.1, 3.4 and 3.7

respectively. The magnitude of extensibi1ity dependsupon the compactness of threads. With increase in thecompactness of thread, the elongation of the threaddecreases. Since the TM changes from 3.1 to 3.7, thecompactness of weft threads increases and con­sequently the extensibility of threads decreases. Thecorrelation between TM and elongation has beenfound to be linear and statistically significant, thevalue of coefficient of correlation being -0.99. Theseresults are in agreement with the findings of Weiner 3 .

Effect of weft TM on tearing strength-To study theeffect of twist multiplier on the tearing strength of thefabric, three different TMs were selected. It is observedfrom Fig. 3 that increase in weft TM decreases theweft-wise tearing strength of the fabric when the warpparticulars are kept constant. Hamburger 9 alsoreported that the most important factor whichinfluences the tearing strength of the fabric is itssurface or yarn-to-fabric friction. Increase in TMcauses a corresponding decrease in the elongation of

107

INDIAN J TEXT. RES., VOL. 8, DECEMBER 1983

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Fig. 5-Relationship between f/f, and tearing strength

46 50 55PICKS/in

Fig. 7-EfTect of picks/in on crimp level (0-0-0) and tearingstrength (0 ... 0 ... 0)

crossing points or frictional points per unit area of thefabric. With increase in pick level, cloth cover increasesand thus the fabric ahead of del jams earlier in thedirection of tear and the extent of yarn movement inthat direction is lesser. This causes the del to comprisefewer yarns, resulting in a fall in the tearing strength.

This effect may also be explained on the basis of thecover factor. As the pick level increases in a wovenfabric, its cover factor increases (Fig. 8).The computedvalue of coefficient of correlation between tearstrength and fabric density across the direction of tear

2 4 6 8 10

CRIMP, .,.

Fig. 6-Relationship between crimp level and warp-wise tearing.'strength

extensibility of weft threads decreased, which resultedin a lower value of tearing strength. In the third case,the weft count was further increased to 2/40s, whichled to further decrease in the extensibility of weftthreads. This further decrease in weft threadextensibility reduced the number of threads in the del,which in turn reduced the tearing strength. Hence, itmay be concluded that with increase in the extensibilityof threads, tearing strength increases.

Effec,t of withdrawalforce on thread strength-Dataon the tearing strength and the ratio between thebreaking strength of weft (f) and the withdrawal forceof wefti(f.) are presented in Fig. 5. It is observed thattearing/strength increases as the ratio off/fs increases.This is in agreement with the finding of O'Brien andWeine~3, that breaking strength divided by the pull­out force for the opposite set of thread is directlypropor,tional to the tearing strength, because withultimate increase in the yarn withdrawal force, the dellimits itself within a smaller area and depth, bringingfewer yarns into action. Obviously, the supportingcapacity of the del system is reduced and a lowertearing strength is recorded .

Effect of crimp on tearing strength-It is observedfrom Fig. 6 that the crimp has a linear relationship withthe tearing strength of the fabric with the value ofcoefficient of correlation as -0.99. This is inagreement with the finding ofWeiner3 , who reportedthat the crimp of the threads in a cloth causes areduction in the case of slippage that arises from ahigher crimp because of the yarn bent to a greaterextent. With a lower crimp, the area of contact amongthe threads would be smaller and the frictionalresistance to the movement would be less.

Increase in pick level increases the crimp level (Fig.7) and thereby the elongation also increases. Increasein elongation becomes the root cause of decrease intearing strength, as stated earlier. Another factorinfluencing the crimp is the weave. The number oftimes!the weft changes its face in I in also affects thecrimp level. The weft in a plain woven fabric changesits face for the maximum number of times and thus hasthe highest value of crimp, while reverse is the case with4-thread satin. Due to this, the withdrawal force ofthread, or the thread pulling out force, is maximum inthe case of plain weave and this results in a lower valueof fabric tearing strength compared that for 4-threadsatin. It may be concluded that the tearing strength offabric has a linear relationship with the crimp level.

Effect of fabric density-The effect of change infabric density (pick/in) on the warp tear strength is alsoshown in Fig. 7. The pick levels used were 46, 50 and55, while the ends/in was constant (52) in all the threecases. It is observed that increase in fabric densityalong the tear direction increases the number of

108

SHARMAet a/.: INFLUENCE OF YARN& FABRICPROPERTIES ON TEARING STRENGTHOF FABRICS

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a

WEAVE - PLAIN 0WARP COUNT-2/40s

9.0~WE FT COUNT-2/36 s

0·048 0,050 0-052 0,054RECIPROCAL OF CLOTH COVER FACTOR

Fig. 8-Relationship betweenreciprocalof cloth cover factor andtearing strength

elongation is followed by increase in the weft-wisetearing strength of the fabric.

(2) With increase in pick level, there is acorresponding decrease in the warp-wise tearingstrength.

(3) The tearing strength is directly proportional tothe thread breaking strength.

(4) The tearing strength increases with decrease inthe thread pulling out force.

(5) Increase in float length increases the tearingstrength, thus giving a high value of tearing strength inthe case of 4-thread satin as compared to plain or twill

Table I-Effect of Weave on Tearing Strength

Sample

WeaveWarpWeftWarpWeftNo.

pulloutpullouttearingtearingforce

forcestrengthstrengthg

gkgkgI

1/1 Plain36506.887.162

3/1 Right12187.938.34hand twill 3

2/2 Right10168.418.54hand twill 4

4-Thread8148.789.35satin

Conclusions

(I) Increase in weft count causes a correspondingdecrease in the weft-wise tearing strength due to theless number of fibres in the cross-section. Increase in

weft twist multiplier decreases proportionately theweft-wise tearing strength of the fabric. Increase in

is negative. This finding is in agreement with that ofBacker10, who reported that the tearing strength of afabric is closely related to the reciprocal of the coverfactor.

Effect of weight on tearing strength-Therelationship between weight/m2 (warp-way and weft­way) and tearing strength is shown in Fig. 9. Therelationship is seen to be linear. It may be concludedthat with increase in weight/m2 or weight per unit areaof the fabric, there is a corresponding increase in thetearing strength of the fabric as well as in the weftdirection. This finding is in agreement with that ofGanatra and Munshi 11 .

Effect of weave on tearing strength-While studyingthe effect of various weaves, it was observed that thetearing strength of the fabric increases with increase infloat length. This is in conformity with the findings ofHamburger9, who found that a fabric having longerfloats generally has a higher tearing strength than theone having shorter floats. He also observed that plainwoven fabrics exhibit the minimum tearing strengthdue to the greater number of intersections in the weave.Apparently, the plain intersection provides betterbinding than that obtained by the passage of yarnmerely from one end of the cloth to the other; the resultis presumely due to the greater mutual yarn pressurewhich must exist at the plain intersection.

In a weave with many crossovers/in, the grippingsection between the warp and weft threads has beenfound to be high and thus increases the ratio betweenthe yarn withdrawal force and the yarn breakingstrength in opposite direction over what it would havebeen for a fabric with longer floats. This.increase in thepullout force resulting from the weave reducesconsiderably the tear strength of the fabric (for a givenyarn strength and texture). Thus, the plain weave hasbeen found to be weaker than 2/2 twill, 3/1 twill and 4­thread satin. A looser weave with longer floats alsoallowed a greater trellis type distortion. Themagnitude of the tearing strength also depends uponthe type of material used, yarn construction and other'cloth parameters, as discussed earlier. The 2/2 twill hashigher tearing strength than 3/1 twill, because it haslower value for the pullout force. The weave affects thetearing strength of the fabric, because it is closelyrelated to the float length and the pullout force, whichhave direct influence on the tearing strength of a fabric(Table I).

109

INDIAN J TEXT. RES., VOL. 8, DECEMBER 1983

structures. The tearing strength of 2/2 twill is higherthan that of 3/1 twill, as the withdrawal force for 3/1twill is·higher.

(6) Increase in crimp decreases the tearing strengthof the fabric.

(7) The tearing strength of the fabric is dependentupon the inter-yarn spacing or cover factor.

(8) With increase in wt/m2 of a fabric, tearingstrength increases in both warp and weft directions.

(9) The ratio of single thread strength to the pulloutforce for the opposite set of threads is directly relatedto the tearing strength.

AcknowledgementThe authors express their thanks to Prof. R.C.D.

Kaushik, Director TIT, Bhiwani, for permission to

110

publish this paper. They are also thankful to thepersonnel of Bhiwani Textile Mills, Bhiwani, for theircooperation.

References

I Krook C M & Fox K R, Text Res J, 15 (1945) P389.2 Millard F J, J Text Inst, 38 (1947) T419.3 O'Brien W E & Weiner L I, Text Res J, 24 (1954) P241.4 Morton W E & Turner A J, J Text Inst, 19 (1928) T189.5 Backer S & Tanenhaus S J, Text Res J, 21 (1951) P635.6 Indian Standard specifications IS:2693 (Indian Standards

Institution, New Delhi).7 Taylor H M, J Text Inst, 50 (1959) Tl61.8 Turner A J, J Text Inst, 11 (1920) 181.9 TeixeiraN A,Platt M M & HamburgerW J, Text ResJ,25(1955)

838.

10 Backer S, Text Res J, 22 (1952) 435.II Ganatra S R & Munshi V G, Indian J Text Res,S (1980) 108.