PSI - Issue 14

Hemant Chouhan et al. / Procedia Structural Integrity 14 (2019) 830–838 Author name / Structural Integrity Procedia 00 (2018) 000–000

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1. Introduction Fiber reinforced plastic composites due to their high specific strength and modulus coupled with low density has taken over the conventional metals and alloys for majority of engineering and defense applications. Depending on the type of application a variety of fiber options are available to suit the specific requirements. In general, glass fibers are preferred for general engineering applications; carbon fibers are primarily used for aerospace application and Kevlar for ballistic and high strain rate applications. Ultra-High Molecular Weight Polyethylene (UHMWPE) has emerged as the new class of fibers for high strain rate applications. UHMWPE fiber-based composite solutions are lighter and performing better over other fiber types based composites. Uses of thermoplastic and synthetic rubber based matrices further enhance the performance of UHMWPE composites Allazadeh et al. (2012) . In general, majority of materials disclose rate-dependent behavior. The rate-dependent behavior of different materials including composites is discussed in the literature by Allazadeh et al. (2012) and Sanchez-Galvez et al. (2014). Eslami et al. (2012) reported that environmental variables like moisture retention and temperature debase the static and dynamic mechanical properties of a polymer and fibers in an FRP composite. The security personnel using a composite protective armor may experience comparative extraordinary climate conditions. For the most part, environmental temperature variation is within the admissible scope of polymer framework properties to the extent their usefulness is concerned. However, moisture ingestion may vary the properties of a composite system. Both the polymer and fiber may associate at the substance level with the moisture and leakage of moisture can prompt swelling or delamination. The high strain rate conduct of S2-Glass – Vinyl ester woven composite under the impact of moisture and temperature uncovers a decrease in quality as a function of moisture ingestion and higher rate affectability factor for wet composite is reported by Haque et al. (2003). An examination on Kevlar-epoxy composite affected by various ecological arrangements uncovers that an impacted specimen, when immersed in salt water, demonstrates an adjustment in properties contrasted with un-impacted specimen when dunked in salt water. In like manner, acid dipped and hydraulic oil dunking also brings about lower quality as reported by Manikandan et al. (2013). Critical research is placed in to think about the rate-dependent conduct of different thermosetting polymer composite affected by moisture. Be that as it may, little data is accessible about high strain rate reaction of thermoplastic matrix based composite affected by moisture. This being operational for the security workforce, there is a strong need to comprehend the dry and wet UHMWPE-thermoplastic composite response under high strain rate loading. The presented work focuses on the effect of moisture on the rate-dependent conduct of UHMWPE fiber based composite with synthetic rubber based matrix. 2. Experimental Setup The necessity of performing the compressive high strain testing of composites was fulfilled by the development of a split Hopkinson Pressure Bar (SHPB) setup. The SHPB set-up principally consists of a gas gun, striker bar, incident bar, transmission bar, momentum trap, speed sensor, signal conditioner-amplifier and data acquisition system and information obtaining framework is presented in Fig. 1 and details of key components are exhibited in Table 1. A suitable pulse shaper is recommended in literature to minimize noise and to smoothen and modify the incident pulse by Vecchio et al. (2007). Linatex, a natural rubber in circular shape having 1.3mm thickness is used as pulse shaper. The complete specifications and subtle elements of the set-up are accessible in the literature Chouhan et al. (2017). One-dimensional wave propagation theory is utilized to compute stress, strain and strain rate prompted in the specimen. 2.1 Sample Preparation A 16 layered composite laminate was made of UHMWPE fiber-based composite with synthetic rubber as matrix material (UHMWPE-SR). The usually utilized grades of synthetic rubber are D1107 (Styrene Isoprene Styrene (SIS) Block Copolymer) and G1650 (Styrene Ethylene Butylene Styrene (SEBS) Triblock Copolymer) by