Volume-7, Issue-1, January-February 2017
International Journal of Engineering and Management Research
Page Number: 284-288
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Strategic Study, Testing and Analysis of Silk Fabric as an Optimum
Application in Bullet Proofing Technology
Satyam Srivastava1, Dr. Prabhat K Sinha2, Nikhlesh N Singh3
1,2,3Department of Mechanical Engineering, Shepherd School of Engineering and Technology, Sam Higginbottom Institute of
Agriculture, Technology and Sciences- Deemed University, Allahabad, Uttar Pradesh, INDIA
ABSTRACT
Sericulture or silk production has a vast and
colorful history unknown to most of the population. There have been lot of studies dealing with the chemical properties of silk but this report is targeted towards strategic study, testing and analysis of silk fabric with respect to their mechanical and physiological properties. With the use of non-renewable resources getting limited every day, it’s the high time that supplementary raw materials need to be looked upon and analyzed so as to replace the resources whose extinction is inevitable. Silkworm silk and spider silkhave been researched hugely in order to substitute man made materials which are on the verge of getting exhausted. Needs of we human beings are infinite and the resources are limited, so this research work has been done focusing on the human needs and their fulfillment. With this approach, few tests such as threads in cloth, fabric thickness, crease recovery angle, stiffness test, yarn count, tearing strength and cover factor have been performed on raw silk fabric and the reports are analyzed thoroughly to give its optimized application in bullet proofing technology. Application of silk in bullet proofing technology is still just a potential use of silk and evidence of silk being a bullet proofing agent has been obtained much before, but our technology is still lagging behind to make silk a certified and sure shot bullet proofing agent.Apart from that silk is used in many fields such as tyre technology, parachute making, comforter filling, artillery gunpowder bags and huge medicinal use. And not to forget its tremendous application in textile industry!
Keywords--Bullet proofing, cover factor, crease recovery angle, fabric, fabric thickness, silk fabric,stiffness test, tearing strength, threads in cloth, yarn count.
I.
INTRODUCTION
Cocoon shells which are produced by silkworm caterpillars are one of the natural structures and polymeric composite materials which exhibit excellent mechanical properties. Silkworm eats mulberry leaves for almost 5-6 weeks with the purpose of storing enough nutrients and
becoming capable of shedding their skin for almost five times. By doing this silkworm larvae start constructing protective cocoons on their pupas.
Because of their extraordinary mechanical properties such as Young’s modulus and strength, natural silk fibers produced by silkworms and spiders have gathered tremendous attention in the past decade. Studies on the relationship between their macroscopic properties and multiscale micro- and nano-structures seem to be of special interest, as a means to design and fabricate advanced biomimetic materials.
Investigations on the physical and mechanical properties of these kind of natural polymer composite materials will be of particular significance to gain a deeper understanding of the possible applications of various natural polymers like silkworm silk and spider silk. With advancement in technology and modification in structure, these super polymers can possibly be created artificially and that can act as a boon to the mankind if done successfully. A possible use of silk and spider fiber is in the field of bullet proofing. The first instance of silk being a bullet proofing agent was observed in 1881 when a man was shot twice on his chest but one bullet stopped by a silk handkerchief in his breast pocket which prevented the silk from penetrating. In 1887, George E. Goodfellow wrote an article titled Impenetrability of Silk to Bullets for the Southern California Practitioner documenting the first known instance of bulletproof fabric. He experimented with silk vests resembling medieval gambesons, which used 18 to 30 layers of silk fabric to protect the wearers from penetration.
the coming years. There are uncountable applications of silk apart from being a raw material for clothes and lingerie, upholstery, wall coverings, window treatments (if blended with another fiber), rugs, bedding and wall hangings. However, with upcoming advancements in industrial technology, silk finds many industrial uses as well like parachutes, bicycle tires, comforter filling
and artillerygunpowder bags. OBJECTIVES
The numerous and fruitful uses of silk makes it a material to be researched upon. In theview of the above discussion it was decided to take a study upon the following objectives:
1. To perform a strategic study of raw silk fabrics. 2. To conduct tests of different physiological and mechanical properties of silk fabric.
3. To analyze the properties of silk fabric with useful results.
4. To propose of supposed use of silk in bullet proofing technology.
II.
MATERIALS AND METHOD
Threads in cloth
Anexperiment to investigate number of threads in cloth was performed by IS 1963-1981(RA 2004), Method A, i.e. by traversing thread counter.A portion of one of the pieces constituting the test sample was laid on a flat table and smoothened out. The counting glass with the pointer at zero was placed on the piece in such a way that: (a) On turning the screw the pointer moved in a direction parallel or perpendicular to warp threads, depending upon which set of threads ( warp or weft ) was being counted, and
(b) The pointer coincided either with the right hand or the left-hand edge of a thread, depending on whether the counting is started from right to left or from left to right direction.
Number of warp or weft threads was found by counting the number of units (normally comprising one thread and one space) and including as a fraction, any part of such unit in a distance L, which was supposed to be:
i) 50 mm, if the number of threads are 20 per centimetre (200 per decimetre) or less;
ii) 20 mm, if the number of threads are more than 20 per centimetre (200 per decimetre), but less than or equal to 100 per centimetre (1 000 per decimetre);
iii) 10 mm, if the number of threads are more than 100 per centimetre (1 000 per decimetre).
Following the procedure prescribed above the number of warp and weft threads per centimetre was determined, in four more places evenly distributed along the width and length of the piece and avoiding counting same set of warp or weft threads more than once. The number of warp and weft threads per centimetre was calculated by the following formula:
𝑛 =𝑁
𝐿× 10
Where,
n= number of threads per cm
N = observed number of threads in the distance L
L = distance, expressed in mm, across which the threads are counted; 50 or 20 or 10 mm, as the case may be. For converting the obtained value i.e. in threads per centimeter to threads per inches, multiply it with 2.349. Threads per inch = n × 2.349
Crease Recovery Angle
An experiment to investigate crease recovery angle was performed on silk sample in accordance with IS 4681:1981.
1. Apparatus
Crease Recovery Tester: The instrument
consists of the following essential parts:
a) A circular stole in the vertical plane, graduated in degrees along its periphery and capable of being read to an accuracy of f 0.5” without parallax error.
b) Specimen clamp to hold one limb of the specimen in such a way that the fold lies in a horizontal line on the axis of the circular scale, while the distance between the edge of the grip and the axis shall be about 2 mm. The clamp shall be rotatable so as to adjust the free limb of the specimen in the vertical or horizontal position, depending upon the type of instruments used. \
c) Means for leveling the apparatus.
2. Procedure: Testing equipment was leveled with the help of leveling screws and spirit level. The testing equipment was screened from draughts, operator’s breath and excessive heat radiation from lighting appliances.
Loading: The specimen was folded end to end in
half with its edges gripped in one line with the help of tweezers not more than 5 mm from the ends. The folded specimen was placed on the plate of the loading device and load was applied gently without delay. The load was removed after 5 minutes. The removal of load was to be completed within 0.5 second.
Half the number of test specimens (both in case of warpway and weftway test specimens) were folded face to face and the other half back to back.
Measurement of Recovery Angle
After the load was removed, the specimen was transferred directly to the clamp of the instrument or placed on edge on a smooth horizontal surface. For mounting the specimen in the clamp, one limb of the specimen was held in the tweezers and the other limb was placed in the clamp of the instrument in such a manner as to cause as little disturbance to the angle as possible. If the specimen stands on edge, the mounting of the specimen in the clamp shall be done so that it remains in the clamp at least for 1 minute before the angle is measured.
position. Reading of the crease recovery angle was taken after 5 minutes from the removal of the load.
The angle of recovery was measured for all the warpway( Wp ) and weftway ( Wt ) specimens folded face to face and back to back in the same way. 5 warpway and 5 weftway test specimens for the test were tested for crease recovery angle.
Yarn count
For investigation of yarn count of the specimen silk sample a testing experiment was performed keeping standards from IS 3442-1980 in consideration. The test was performed on the silk sample without removing its sizing or finishing material.
1. Apparatus:
A crimp tester for measuring straightened length of yarn provided with two clamps, the distance between which is adjustable and through one of which a known tension can be applied. Each clamp consists of two metallic jaws, having parallel gripping surfaces.
Balance: A balance capable of weighing correct
to milligrams.
2. Procedure
Warp Yarn:
I. For determining the approximate universal count of the warp yarn in tex, which is necessary for calculating the
tension to be applied during the test, one of the warp way test specimens was taken. Two parallel marks 200 mm apart at right angles to the direction of warp were drawn. Ten warp yarns were removed and cut along the marks with a sharp razor blade and template. The mass of all the yarns was determined in milligrams and approximate universal yarn count was calculated in tex by the following formula:
𝒕 =𝒎
𝟐
Where
t = approximate universal count in tex of the warp yarn m = mass in milligrams of 10 warp yarns
NOTE: It is desired to express the result in any of the traditional count systems.
a) Count in the direct system =𝑴
𝑳× 𝟏𝟎𝟎𝟎 × 𝑪𝟏
Where C1 = a constant corresponding to the count in the direct system in which the result is desired.
b) Count in indirect system = 𝑳
𝑴×𝟏𝟎𝟎𝟎× 𝑪𝟐
Where C2 = a constant corresponding to the count in the indirect system in which the result is desired.
CONSTANS FOR DIRECT COUNT SYSTEM YARN COUNT
SYSTEM
UNIT OF MASS USED
UNIT OF LENGTH USED
UNIT OF YARN COUNT
CONSTANT C1
Denier 1 gram 9000 meters g/9000 m 9
Jute 1 pound 14400 yards Lb/14400 yd 0.02903
Weft Yarn:
I. The crimp and count of the weft yarn were determined by taking the test specimens T1, T2, T3, T4 and T5 by following the same procedure as that of warp yarn.
II. In case the determination of the crimp of the yarn in the fabric is not required and only the count is to be determined, the straightened length and mass of the yarn after desizing may be sued for calculating the count.
CONSTANTS FOR INDIRECT COUNT SYSTEMS YARN COUNT
SYSTEM
UNIT OF LENGTH USED
UNIT OF MASS USED
UNIT OF YARN COUNT
CONSTANT C2
Cotton 840 yards 1 pound 840 yd/lb 590.5
Linen 300 yards 1 pound 300 yd/lb 1654
Spun Silk 840 yards 1 pound 840 yd/lb 590.5
Woolen (Dewsburry)
1 yard 1 ounce 1 yd/oz 31000
Woolen (Yorkshire) 256 yards 1 pound 256 yd/lb 1938
Worsted 560 yards 1 pound 560 yd/lb 885.8
III.
TEARING STRENGTH
The average force, in newtons, required to tear a test specimen over a specified length is known as tearing resistance or tearing strength. For investigation of tearing strength of the specimen silk sample a testing experiment was performed keeping standards from IS 6489-1993 into consideration.
1. Apparatus: Elmendorf tearing tester was used to
investigate the tearing strength of the sample silk specimen.
positioned in the initial start position by raising it clockwise and allowing the release mechanism to secure it. Both sample clamps were opened and 4-ply sample was placed evenly and centrally within both sets of clamp jaws. The clamps were tightened. Integral knife handle was depressed to perform the initial cut. The pointer was moved so that it is touching its stop. The pendulum release was pressed and held down to perform the test. After the tearing swing, as the pendulum made its return swing (clockwise), it was caught gently, so as not to shift the pointer position, and raised again to the initial position, securing it with the release mechanism. The reading was recorded from the scale indicated by the pointer. To avoid parallax error, the reading was taken directly in front of the pointer. Nearest indicated scale division of the pendulum capacity was read. The clamps were opened and the torn paper was removed.
IV.
FLEXURAL RIGIDITY
Flexural rigidity of silk fabric sample was determined by Cantilever fabric stiffness test. The fabric stiffness test was according to the ASTM D 1388-96, Option A manual. Warp way and weft way flexural rigidities were determined by the test and the overall
flexural rigidity was found by the following formula:
Woverall = (Wweft×Wwarp)1/2
The cantilever fabric stiffness tester which was used during the test is shown below:
RESULTS
Number of analysis and testing through different parameters were conducted on the sample specimen of silk fabric and the results thus obtained are listed below:
Threads in cloth specimen of silk fabric was found to be:
1. 118 ends/inch
2. 87 picks/inch
Fabric thickness in cloth specimen of silk fabric was found to be 0.16 mm at CSTRI, Bangalore.
Crease recovery angle in cloth specimen of silk fabric was found to be:
1. Warp- 89°
2. Weft- 98°
3. Total- 187°
Flexural Rigidity in cloth specimen of silk fabric was found to be:
1. Warp- 4.6 mg-cm
2. Weft- 86.7 mg-cm
3. Overall- 20.1 mg-cm
Yarn count in cloth specimen of silk fabric was found to be:
1. Warp- 34.6 den
2. Weft- 114.5 den
Tearing strength in cloth specimen of silk fabric
was found to be:
1. Warp- 1088 gF
2. Weft- 4864 gF
Cover factor in cloth specimen of silk fabric was found to be 18.99 at CSTRI, Bangalore.
V.
CONCLUSION
After study, analysis and testing of silk fabric was conducted through different parameters, it has been obtained that raw silk exhibits fairly low mechanical properties but still has the potential to be used in the field
of bullet proofing. It is an experimentally proven fact that ordinarily if 18-30 layers of silk are employed, the composite will act as a bullet proof wall.
It is suggested that if raw silk is compounded with S or E glass to make a composite then that composite can possibly be used as a bullet proofing agent.
also be used in the bullet proofing technology along with silk.
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