PSI - Issue 14

P Rama Subba Reddy et al. / Procedia Structural Integrity 14 (2019) 676–683 Author name / Structural Integrity Procedia 00 (2018) 000–000

677

2

1. Introduction Advanced polymer composites are being used in military vehicles for various purposes like spall liners, add on armour and structural armour. The role of the armour is to provide protection to the vehicles against kinetic and chemical energy threats. Presence of ceramic and polymer composite materials makes the fighting vehicles light weight, increase its fire power and mobility when compared to traditional steel armour by V. Madhu et al.(2011). During the last two decades various polymer composite laminates have been explored for armour applications such as E-glass, S-glass, Aramid and Ultra high molecular weight polyethylene (UHMWPE) fiber based laminates due to their high specific energy absorption under ballistic impact by MJN Jacobs et al.(2008). Penetration of projectile in composite is influenced by various parameters like fiber volume fraction, type of fiber, its weave pattern, matrix, type of projectile, initial impact energy, etc by RC Laible (1980). Though fibers are the primary energy absorbing materials in composite laminates, role of matrix is also paramount. Matrix restricts the lateral motion of the fibers, helps in direct participation of large volume of fiber materials through dissipation of impact energy to the successive layers during the impact and thus improves the overall energy absorption capability of the composite laminate. Polymer resins like epoxy, phenolic, polyester and polyurea are used for making ballistic grade composites by SS Morye et al. (2000) and E. Sevkat et al. (2009). Among these resins phenolic resins are more preferable for armour applications due to its moderate interlaminate shear strength which promotes for progressive delamination during the impact and also higher temperature resistance. However these resins have got some restrictions like limited storage life, higher production cost, etc. The second choice of the resin for armour composites is epoxy resin, since it has got advantages in-terms of easy of fabrication of various shapes, flexibility in cure cycles and storage life of the resin. Studies have been carried out on effect of thermoplastic and thermoset matrix and its properties on impact performance of the composites. For example Nayak et al. (2012) studied effect of polypropylene (PP) and epoxy matrix on ballistic performance of aramid composite laminates against armour piercing projectiles and found that PP matrix based aramid laminates provided higher ballistic limit and undergoes global mode of deformation. Griffin (1987) conducted ballistic impact experiments with different fiber reinforcements with same matrix and found that damage initiation is governed by the matrix properties and not by the fiber properties. Karthikeyan et al. (2013) studied the effect of shear strength on ballistic response of UHMWPE fibers with two different resin matrices and carbon/epoxy composites under ballistic impact using steel projectiles and found that ballistic performance of the laminate increase with decrease in laminate shear strength. Yet in another study Carrillo et al. (2012) carried out the ballistic performance of thermoplastic/aramid composites using spherical steel projectile and observed that addition of thermoplastic matrix increases the ballistic performance of composites than the dry fabrics. Gopinath et al. (2012) have carried out comparative study between the resin impregnated composites and clamped dry woven fabric soft body armours using lead projectiles. It was found that the presence of matrix reduces the maximum deflection of the amrour, increases size of the deformed area and enhances the reduction in the kinetic energy of the projectile. James and Gary (1999) studied the effect of laminate properties on ballistic performance of ceramic-composite armour against lead and armour piercing projectiles. It was found that lower resin content, lower laminar shear strength of composites leads to progressive delamination and tensile fiber stretching during impact and thus for more energy absorption in composite armour. Wong et al. (2001) studied effect of matrix on the mechanical and ballistic performance of glass laminates subjected to armour piercing projectiles and drop weight impact tests. Their study revealed an inverse relationship between the G 1C and ballistic V 50 results. Modified phenolic resin show best ballistic performance while epoxy resin shows overall best mechanical and CIA properties of the laminates. Prasanth et al. (2014) have studied the mode-I fracture analysis of thermally aged composite laminates and found that energy release rate of glass composite decreased with ageing. The aim of the present study is to correlate the relation between the mode-I fracture toughness and the ballistic performance of E-glass/epoxy and E-glass/phenolic laminates subjected to mild steel projectile impact. Energy absorption and failure behaviour of the laminates have been studied as a function of thickness.