Special Issue Article JSA JSA J Strain Analysis 47(7) 453–470 Ó IMechE 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0309324712457897 sdj.sagepub.com Ballistic performance of hybrid and non-hybrid composite plates Ercan Sevkat 1 , Benjamin Liaw 2 and Feridun Delale 2 Abstract This paper presents an experimental and numerical study to understand ballistic behavior of plain-weave hybrid and non- hybrid composites. The effect of hybridization on ballistic limit (V 50 ) was investigated. The hybrid S2 glass-IM7 graphite fibers/toughened SC-79 resin, non-hybrid S2 glass-fiber/toughened SC-79 resin, and non-hybrid IM7 graphite fibers/ toughened SC-79 resin composites plates were impacted at various velocities. The three-dimensional dynamic nonlinear finite element code, LS-DYNA, modified with a proposed user-defined nonlinear-orthotropic damage model, was adopted to simulate the experimental results. The combined results obtained from experiments and finite element simu- lations were then used for determining V 50 for each lay-up configuration. Good agreement between experimental and FE results was found from the comparison of dynamic strain and damage patterns. The hybridization found to be very effec- tive on ballistic limit velocities of woven composites. Keywords Hybrid composites, ballistic limit, finite element Date received: 9 January 2012; accepted: 22 June 2012 Introduction Composites made of single fiber or single matrix system may not be adequate to meet the design requirements in some applications. Combining two or more fibers in the same composite will take the advantages of the merits of each fiber system. In most cases, one of the fibers in hybrid composite is high modulus/high-cost fiber such as carbon or boron and the other is low modulus/low-cost fiber such as glass or Kevlar. The high modulus fiber provides the stiffness and load- bearing capability, whereas the low modulus fiber makes the composite more damage tolerant and reduces the cost. Some of the advantages in this approach are the balance of strength and stiffness, reduced weight and/or cost, improved fatigue resis- tance, improved fracture toughness, and impact resis- tance. One of the attractiveness of hybridization approach is the synergy effect that is also called ‘hybrid effect’. The ‘hybrid effect’ is to obtain a composite property whose value is higher than the value predicted from the rule of mixtures. This is called ‘positive hybrid effect’. If the hybrid composite property comes out less than the rule of mixture prediction, it is called ‘negative hybrid effect’. 1 There are many studies on hybrid com- posites under various loading conditions: Tensile, 2 compressive, 3 and flexural. 4 Low-velocity impact response of hybrid composites was also studied exten- sively. 5 In tensile loading condition; ultimate strain and tensile strength were deviated positively from the rule of hybrid mixtures (ROHM); but the modulus of the composite was almost the same with the ROHM pre- diction. Due to the ultimate strain improvement in hybrid composites, hybridization attributed to the bet- ter transverse support and crack arresting characteris- tics in flexural loading conditions. In low-velocity impact studies, high modulus low-density fibers are mixed with low modulus high density and cheaper fibers. Using tougher fiber system as face sheet improved the impact resistance of the composite. The effect of hybridization on ballistic impact per- formance of composites has not been studied ade- quately. Larsson and Svensson 6 used organic fibers along with carbon fibers in the same composite. Introduction of organic fibers increased the ballistic 1 Department of Mechanical Engineering, Meliksah University, Turkey 2 Department of Mechanical Engineering, The City College of New York, USA Corresponding author: Ercan Sevkat, Department of Mechanical Engineering, Meliksah University, Talas 38280, Kayseri, Turkey. Email: esevkat@meliksah.edu.tr