FUTURISTIC MATERIALS BASED ON CARBON NANOTUBES FOR DEFENCE APPICATIONS A CASE STUDY

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FUTURISTIC MATERIALS BASED ON CARBON NANOTUBES FOR DEFENCE APPICATIONS A CASE STUDY Abrar Shaik 1 and Revanasiddappa 2* 1 Department of Mechanical Engineering, 2 Department of Engineering Chemistry,

1 FUTURISTIC MATERIALS BASED ON CARBON NANOTUBES FOR DEFENCE APPICATIONS A CASE STUDY Abrar Shaik 1 and Revanasiddappa 2* 1 Department of Mechanical Engineering, 2 Department of Engineering Chemistry, Hosur Road, PESIT Bangalore South Campus, Bangalore Abstract- Composite materials have been exclusively used in various technological industries in the world. Defence is one of the major users of composite materials. The invention and subsequent growth of composite materials has brought a revolution to the world. The composite materials industry has grown at a phenomenal rate. Defence industries being the major beneficiaries of their tremendous growth. One of the needs of the defence industry has been the need for wider performance range materials for armours. This includes better energy absorption, light weight etc. Since the energy absorption in composites primarily occurs due to elongation and failure of fiber, materials with high tensile strength and high strain to failure are the best choice. In addition, high elasticity in the material can lead to better ballistic performance due to its ability to spread out energy to larger areas. So there is need for materials which show better ballistic performances than the existing ones. This paper is intended to summarize the use of carbon nanotubes in designing of bulletproof vests which actually rebounds the force of the bullet because of its exciting properties like good strength, lightweight and good energy absorption. Keywords-Carbon nanotubes; Defence; INTRODUCTION hybridization [3]. The chemical bonding of nanotubes is composed entirely of sp 2 bonds, similar to those of graphite. This bonding structure, which is stronger than sp 3 bonds found in diamond, provides the molecule with unique strength [6]. Nanotubes normally align themselves into ropes held together by Vander Walls forces. Nanotubes can merge together under high pressure trading some sp 2 bonds for sp 3 bonds, giving the possibility of producing strong, unlimited length wire through high pressure nanotube linking [5]. The fiber made up of tiny carbon nanotubes is very strong, lightweight, very good energy absorption. Inherent property of elasticity is the main reason for it. This material is already up to several times stiffer, tougher and stronger than currently used fibers like Kevlar, dyneema which are used to make protective body armours, TYPES OF CARBON NANOTUBES Carbon nanotubes are of different types. They are: SINGLE-WALLED CARBON NANOTUBES- The science of the almost incomprehensibly small devices has been brought closer and closer by the multidisciplinary field of nanotechnology. The effects of these developments will at some point be so immeasurable that they will probably influence all fields of science and technology. A nanometer is one-billionth of a meter, or about one ten-thousandth of the thickness of the human hair. The nature of bending of a nanotube is described by applied quantum chemistry, specifically, orbital Fig. 1- Structures of different types of SWCNTs

The integer s n and m denote the number of unit vectors along two directions in the honeycomb crystal lattice of graphene.

2 Most Single-Walled Nanotubes (SWCNT) have a diameter of close to 1 nanometer, with a tube length that can be thousands of times longer. They are formed by rolling a sheet of graphene into a cylinder along an (n, m) lattice vector in graphene plane. The integer s n and m denote the number of unit vectors along two directions in the honeycomb crystal lattice of graphene. If m = 0, the Nanotubes are called "zigzag, which is named for the pattern of hexagons as we move on circumference of the tube. If m = n, the Nanotubes are called "armchair", which describes one of the two confirmers of cyclohexene a hexagon of carbon atoms. Otherwise, they are called "chiral", in which the m value lies between zigzag and armchair structures. The word chiral means handedness and it indicates that the tubes may twist in either direction [3]. MULTI-WALLED CARBON NANOTUBE MECHANISM OF BULLETPROOF VESTS Fig. 3-Bullet strike in bulletproof vest Like a soccer goal s net absorbs the ball s energy and spreads it out across all the fibers in the net, adequately slowing and then stopping the ball s leading movement, the tightly-woven, flexible synthetic fibers in a bulletproof vest do the same thing as shown in Fig. 3. Before the bullet can pass through the body and cause terrible injury or even death, the fibers in the vest catch the bullet and bring it to a stop. If you ve ever seen a soccer ball kicked into a goal, you know that the net gives way and permits the ball to travel a little ways before it stops it and brings it to the ground. Bulletproof vests cannot give that much, however. Fig. 2-Structure of MWCNT This is the reason why the fibers in a bulletproof vest must be packed in sync much more firmly. They are so densely packed that you could think of them as numerous soccer goal nets overlapped and accumulated on top of each other thousands and thousands of times over in a tiny space. There are two structural models of multi-walled nanotubes. In the Russian Doll model, a carbon nanotube contains another nanotube inside it (the inner nanotube has a smaller diameter than the outer nanotube). In the Parchment model, a single graphene sheet is rolled around itself time and again, resembling a rolled up scroll of paper. Multi-walled carbon nanotubes have much the same properties to single-walled nanotubes, yet the outer walls on multiwalled nanotubes can safeguard the inner carbon nanotubes from chemical interactions with foreign materials [5]. Among the two types, single walled nanotubes can be used in making of protective body armours. High performance fibers and yarns frequently used in practice today for ballistic protection are S-glass, highly oriented ultra high molecular weight polyethylene (e.g., Dyneema, Spectra), aramids (e.g., Kevlar 29, Kevlar 49, Kevlar 129, Kevlar KM2, Twaron), PBO (e.g., Zylon) which is a p-phenylene- 2-6-benzobisoxazole, new polymeric fibers such as Polypyridobisimidazole (PIPD) (referred to as M5) etc [1]. High-energy absorption capacity, resistance to thermal degradation, high tensile, high rupture strain, compressive strength and low density describes the fibers. Presently, bullet-proof vests are primarily made from high stiffness and toughness, woven or laminated, polymeric fibers stacked in a number of layers. The fabric material absorbs the energy by stretching of the fibers and the stiff fibers ensure that the load is

dispersed over a large area all over the material when the bullet strikes. This process decelerates the bullet and finally stops it from penetrating the body.

3 dispersed over a large area all over the material when the bullet strikes. This process decelerates the bullet and finally stops it from penetrating the body. In case of polymer matrix composites (PMCs), the ability of a fiber to deform is severely prevented due to the existence of surrounding resin, and therefore, the energy absorption capacity is reduced. The main failure mechanisms in PMCs under ballistic impact are straining of fiber and its delamination, fracture and shear deformation in the resin matrix. Hard body armour has been developed to provide greater protection against blunt trauma and higher velocity ammunition. It includes a rigid facing comprising ceramic inserts, steel or titanium panels and a ballistic fabric backing. The kinetic energy of the projectile is absorbed and dissipated in localized shattering of this ceramic tile and blunting of the bullet material during its impact on the ceramic of hard armour. POTENTIAL OF CARBON NANOTUBES FOR BALLISTIC ARMOUR Carbon nanotube (CNT) is an optimal candidate material for bulletproof vests due to its unique combination of exceptionally high yield strain and high elastic modulus. A Young's modulus of about 1000 GPa, strength ranging between GPa, and strain at tensile failure predicted to be as high as 16% typically characterize SWCNTs14. Assuming that the specific gravity of SWCNT is about 1.4 g/cm3, one can estimate the ballistic performance parameter to range between 2708 m/s and 4326 m/s. These values are in agreement with the previously reported value of 3000 m/s by Alan Windle for the ballistic performance parameter of carbon nanotubes. If one compares these values with those for other fibers suitable for ballistic applications, the enormous potential of CNTs as a candidate material for bulletproof armor system is quite evident [1]. This is very much clear from Fig. 4. Fig. 4- Specific energy absorption capacity as a function of sonic velocity for selected high performance fibers. There are three distinct accesses for utilizing carbon nanotubes to improve the ballistic performance of body armor. These are: 1) Reinforcing the armor grade fibers like Kevlar with CNTs to enhance their elastic modulus and energy absorption capacity 2) Usage of neat or composite fibers of CNTs in the form of woven or non-woven fabric, for achieving remarkable ballistic performance. 3) Fusion of CNTs into PMCs, metals or ceramics to improve their strength and erosion resistance The advancement of nanofibers could lead to lighter and tougher polymer composites. Ireland s trinity college and the University of Texas have whirled carbon nanotube composites with toughness in the order of seventeen times that of Kevlar [2]. A research paper published by the engineers from the centre of Advanced Materials Technology details a way to use the elasticity of carbon nanotubes to not only stop bullets penetrating material but actually rebounding their force. By examining the ballistic impact and bouncing-back processes on carbon nanotubes,this investigation shows that nanotubes with larger radii can withstand higher bullet speeds and the ballistic resistance is the maximum when the bullet hits the center of carbon nanotubes [2]. The ballistic resistance of carbon nanotubes will remain the same on consequent bullet strikes if the impact is after a small interval of time. This attribute of carbon nanotubes can also provide the armor improved protection against blunt trauma effects. Researchers from Lockheed Martin Corp. have

4 developed a hybrid composite containing fibrous reinforcement, wherein the polymer matrix is enhanced by the additions of either SWCNTs or MWCNTs (or combination of both). The fusion of the CNTs in the PMC based armor results in enhanced ballistic properties and is reflected in convincing reduction in the projectile velocity as determined by the V50 ballistic test [1]. The above ballistic material developed is promising for applications in personal body armor, aircraft, ships, and armored vehicles. CONCLUSION The use of carbon nanotubes in making of protective body armour will be very efficient for the years in the future. These are highly safe and available easily at reasonable prices than the armours which are currently being used. Over the next few years it is widely anticipated that the use of carbon nanotubes will continue to expand in other applications of defence. REFERENCES [1] Y.R. Mahajan. (2010, August 10). Carbon nanotubes and the pursuit of body armor [online]. Available: [2] M. Dhinesh Paneer and J.Arun Jacob Packianathan, Ballistic resitance using carbon nanotubes, Unpublished. [3] [4] [5] Chris Scoville, Robin Cole, Jason Hogg, Omar Farooque and Archie Rusell, Carbon Nanotubes. [6] Nanotubes

A Constitutive Model for DYNEEMA UD composites

A Constitutive Model for DYNEEMA UD composites L Iannucci 1, D J Pope 2, M Dalzell 2 1 Imperial College, Department of Aeronautics London, SW7 2AZ l.iannucci@imperial.ac.uk 2 Dstl, Porton Down, Salisbury,