IJRET: International Journal of Research in Engineering and TechnologyeISSN: 2319-1163 | pISSN: 2321-7308 _______________________________________________________________________________________ Volume: 03 Issue: 08 | Aug-2014, Available @ http://www.ijret.org 295 A NOVEL APPROACH FOR DETECTING, LOCALISING AND CHARACTERISING DAMAGES IN GLASS FIBRE REINFORCED POLYMER (GFRP) USING THE DROP WEIGHT IMPACT TESTER N. Razali 1 , M.T.H. Sultan 2 1 Aerospace Manufacturing Research Centre (AMRC), Level 7, Tower Block, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor DarulEhsan, Malaysia 2 Aerospace Manufacturing Research Centre (AMRC), Level 7, Tower Block, Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor DarulEhsan, Malaysia Abstract The aim of this work is to conduct an experimental study of a low velocity impact test by changes in the type of materials, number of layers and impact energy level using an IM10 Drop Weight Impact Tester. The composite material used in this study was Glass Fibre Reinforced Polymer (GFRP) in two forms:Type C-glass 600 g/m 2 and Type E-glass 600 g/m 2 . These materials were fabricated using a hand lay-up technique to produce laminated plate specimens with a dimension of 100 mm × 150 mm. Each type of specimen was fabricated into 10 layers, 12 layers and 14 layers of GFRP woven roving plies. The low velocity impact test was performed using an IM10 Drop Weight Impact Tester with 10 mm hemispherical striker cap. The impact energy was set to 14, 28, 42 and 56 Joule with velocity ranging from 1.73 m/s to 3.52 m/s for 10 layer specimens and 7, 14, 21, 28, 35, 42, 49 and 56 Joule for 12 layer and 14 layer specimens. The relationships between impact energy andimpact force, displacement, damage area and energy absorbed are presented. The comparison and behaviour between the two types of GFRP is discussed. Keywords: Low Velocity Impact (LVI), Glass Fibre Reinforced Polymer (GFRP), Energy Absorbed, Drop Weight Impact Tester ---------------------------------------------------------------------***--------------------------------------------------------------------- 1. INTRODUCTION Since composites were introduced in industry, damage from unexpected impact eventse.g.the dropping of hand tools during maintenance work,has seemed to be a problem. A study has been conducted over a few types of compositesconcerning impact damage [1-4]. A low velocity impact (LVI) - which is less than 11 m/s - may cause damage [5]. However, some consider impact velocities for LVI to beup to 40 m/s [6]. When this material issubjected to low velocity impacts, the structural integrity, stiffness and toughness of the material are all significantly reduced and this will lead to the catastrophic failure of the structure [7]. The possible damage mechanisms that composite laminates may face in the event of low velocity impacts are delimitation, matrix cracking, matrix breakage, fibre cracking, fibre breakage, and fibre pullout [8]. In low- velocity impacts, internal damage is hard to detect, but it may considerably reduce the capacity of the laminate to support loads. It is therefore important to relate the shape and dimensions of the damage to the geometric characteristics of the sample, the boundary conditions and the test parameters (impact velocity, energy, maximum force, etc.), to better understand the damage mechanisms [9].Due to the increasing focus on the impact problem, it is important to study low velocity impact damage. According to Tita, if an object with mass  impacts a composite plate with a velocity   , the impact energy of the impacter   can be expressed by Equation 1 [10]:       (1) The characterisation of the impact tests was based on the conservation of energy principle, where the potential energy (PE) before the impact event is assumed to be equal to the kinetic energy (KE) after the impact event [11,12]. Based on Sultan et al.[13],this leads to an impact velocity as shown in Eq. (2):   √ (2) where v = velocity at impact, h = drop height, and g = acceleration ofgravity. Most composites are brittle and so can only absorb energy in elastic deformation and through damage mechanisms, and not by plastic deformation [14]. From Mathivanan’s paper, the energy absorbed can be calculated using the area under the graph of force versus displacement as shown in Figure 1.