PSI - Issue 14

C.Jayarami Reddy et al. / Procedia Structural Integrity 14 (2019) 634–641 C.Jayarami Reddy / Structural Integrity Procedia 00 (2018) 000–000

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1. Introduction Recently, the prime focus of the military research community has been to develop advanced light weight materials for protection against stupendously growing IED attacks and explosive blast. Polymer matrix composites have been extensively studied for aerospace and military applications due to their light weight and good energy absorbing capabilities as reviewed by Mauritz et al. (2001) and Ye L., et al. (2005). Comptois (1999) and his team studied the effect of standoff distance of small charges on unidirectional carbon and woven glass fibre reinforced epoxy composites. The damage modes observed on composites for surface and stood off charges are, hole formation and delamination. These damage modes were also increased with increase in blast impulse. Franz T., et al. (2002) investigated the response of chopped strand-mat glass fibre reinforced poly ester laminates to air blast loading. Three modes of failure such as matrix cracking, delamination /debonding and penetration were observed in the composite target when subjected to air blast loading. The effect of areal density of composites on the damage mode and damage propagation was also studied. The response of carbon fibre reinforced thermoset and thermoplastic composites against explosive blast loads was studied by Yazhid et al. (2011) and found that there is no effect of matrix on the damage of the composites. Xin Li et al. (2017) studied the blast response of flat and curved panels of balsa/epoxy composites and reported that the damage extent of the composites increase with increase in blast impulse and reduces with increase in thickness of the composites. The behavior of fibre reinforced composites against underwater blast was extensively studied by Mauritz et al. (1994, 1995). In all the above reported studies, the composites were fabricated using the solid fibers. However, no studies were reported on the blast response of hollow fibre based composites. H-glass fibre reinforced polymer composites are being widely used in aerospace industry for radome applications due to their light weight, better compression strength and dielectric properties. As reported by Bazhenov S L., et al. (1992) and Bley S M., et al. (1996) hollow glass fibres are also thought to offer increased compressive strength by improving fibre alignment within the composite and by increasing the resistance of fibres to microbuckling or kink band formation. Martin hucker et al. (2003) studied the compression properties of unidirectional hollow glass/epoxy composites and found that fibres with hollow fractions of 20-25% may offer significant improvement in compression properties. Comparative studies on mechanical properties of solid and hollow glass fiber laminates were carried out by Boniface L., et al. (1998). Due to the aforementioned advantages of hollow glass fibers and their composites they can be used as potential blast mitigating material. However, to use them effectively, it is very essential to understand their dynamic behavior under different blast loads. In the present study, the response of hollow glass fibre reinforced composites to air blast loading was studied under different blast conditions. The blast conditions were varied by changing the distance between the explosive and the target plates (SoD). The fabrication and mechanical property testing of H-glass and E-glass composites were also included in this paper. The effect of the SoD on the magnitude of pressure was also studied. The damage modes of the H-glass composites at different blast loading conditions were discussed and were compared with E-glass composites. The performance of the H-glass composites was also compared with the solid E-glass composites. 2. Experimental 2.1. Materials & Measurements The plain weave woven rovings of H-glass and E-glass were purchased from R&G Faserverbundwerkstoffe, GmbH (Germany) and M/s.Ovens Cornings, India, respectively. The areal weights of the H-glass and E-glass woven rovings were 300gsm and 360 gsm, respectively. These rovings were used as reinforcements in the fabrication of composites. The Fineset ® - 1556 epoxy resin and Fineset ® - 1972 amine based hardener were supplied by M/s. Fine Finish Organic chemicals, Mumbai. The resin and hardener were used in 100:60 weight ratio to prepare prepregs and composite laminates, consequently. Plastic explosive, PEK-1 of TNT equivalence factor 1.17, was used as an explosive charge in all the blast experiments. The explosive was molded into a spherical shape and was initiated by using electric detonator –33. The incident pressure or peak over pressure and reflected pressure were recorded using piezoelectric pencil probe (Make: PCB, Model No. 137B22A) and piezo - electric pressure sensors, respectively. All the pressure sensors,