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

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2. Experimental 2.1. Materials

The laminates were prepared using epoxy resin (LY1556) with hardener (HY5200) procured from M/s. Fine Finish organics Pvt. Ltd, Mumbai and phenolic resin was supplied by M/s. Permali Wallace Pvt Ltd, Bhopal. Commercially available E-glass woven roving is used as reinforcement. The basic properties of the glass roving are 0.25mm thickness, areal density is 360 GSM and warp and weft is 55x50 per 10 cm. 2.2. Fabrication of composite laminates E-glass/epoxy and E-glass/phenolic composite laminates of size 350 mm x 350 mm with thicknesses varying from 5 to 35 mm are made through hand layup technique followed by hot pressing under hydraulic pressure. Cure cycle for both the laminates were followed as per the resin manufacturer’s instructions. Phenolic resin based laminates were cured at 160 o C in hydraulic press under 40 bar pressure for 180 minutes. While epoxy resin based laminates were cured at 120 o C two hours followed by 160 o C three hours under 40 bar pressure for achieving the complete curing of the laminates. Curing condition of the laminates was confirmed by determining glass transition temperature (T g ) on final cured laminates using DSC technique. Physical and mechanical properties of the laminate like resin content, density, barcol hardness, tensile, flexural, inter laminar shear strength (ILSS) and dynamic mechanical analysis were evaluated as per ASTM test methods. 2.3. Determination of fracture energy Mode-I fracture energy test was performed according to ASTM D5528 to measure the fracture energies required for delamination. Both E-glass/epoxy and E-glass/phenolic composite laminates were fabricated with pre delamination of 50mm depth. Metallic grips were bonded to the laminate for carrying the test in tensile mode as shown in schematic drawing at Fig.1(a). Universal testing machine (UTM) (Model: Instron 4505) was used to carry out the test. The experimental setup for carrying out the test is shown in Fig.1(b).

Fig.1. (a) Schematic drawing of Mode-I Fracture energy test specimen and (b) test setup on UTM machine

2.4. Ballistic impact tests To The ultimate use of composite as armour material will be against ballistic threats. Hence it is essential to evaluate the behaviour of composite laminates under ballistic impact conditions. The tests were carried out using powder guns in a closed firing range. Detail of ballistic experimental setup is given in our previously published work (Rama Subba Reddy et al. 2016). In the present study, tests were carried out with 7.62 x 39 mm caliber MS core projectile fired from AK-47 rifle. The target plate was kept at 10 m distance from the muzzle end of the gun and projectile was impacted on target plate at an angle of 90° to the line of sight. The size of the target plate was 150mm X 150mm and minimum five specimens were prepared for each set of experiments. Strike and residual velocities of the projectile were measured by placing infra red based light gates velocity measuring system (Make: MS Instruments) before and after the target. Energy absorption of the composite laminates is calculated based on projectile strike and residual velocities using the given formula.