PSI - Issue 28

Theodosios Stergiou et al. / Procedia Structural Integrity 28 (2020) 1258–1266 T. Stergiou et al. / Structural Integrity Procedia 00 (2019) 000–000

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4. Conclusions In this paper, the ballistic performance of thin laminate targets was assessed for the case of polyurea-coated aluminium plates, under impact with a rigid spherical projectile with dimensions much higher than the thickness of the metallic substrate. The detailed results were compared to those for the monolithic case. For the first time, a custom polyurea model was successfully utilised within a finite-element framework for a sub-ordnance impact velocity scenario of thin metallic targets. The layered configuration provided increased ballistic performance for a polyurea thickness in excess of 4 mm. The laminate structure translated to an areal density equivalent to monolithic aluminium of 4.92 mm thickness, i.e. an increase of 1.4 mm. The ballistic-performance deterioration with the introduction of thin polyurea layers, below 4 mm, was due to the loss of bending capacity, a primary energy absorbing mechanism of thin metallic plates at sub ordnance velocities. The loss occurred due to perturbation disturbances between the frontal and substrate layers, resulting in a deformation-dominant localised response. At low polyurea thicknesses, the membrane strength of the coating is inadequate for counterbalance of the energy absorbing capacity due to plate bending. Evidently, changes to the stoichiometry and manufacturing parameters that affect the ultimate strength and other key mechanical properties should have an impact on polyurea membrane strength and energy absorbing capacity. Such changes are expected to change the ballistic performance capabilities of the frontal polyurea coating. Future research will be carried out to examine the sensitivity of the laminate target’s ballistic performance to the mechanical properties of the polymeric layer. Almohandes, A. A., Abdel-Kader, M. & Eleiche, A., 1996. Experimental investigation of the ballistic response of steel-fiberglass reinforced polyester laminated plates. Composites, 27(B), 447-458. Amini, M. R., Isaacs, J. B. & Nemat-Nasser, S., 2010. Experimental investigation of response of monolithic and bilayer plates to impulsive loads. International Journal of Impact Engineering, 82-89. Barsoum, R. G., 2015. Elastomeric Polymers with High Rate Sensitivity: Applications in Blast, Shockwave and Penetration Mechanics:Elsevier. Bergström, J. S. & Boyce, M. C., 1998. Constitutive modeling of the large strain time-dependent behavior of elastomers. Journal of the Mechanics and Physics of Solids, 931-954. Boyce, M. C., Liana, P. G. & Socrate, S., 2000. Constitutive model for the finite deformation stress-strain behavior of poly(ethylene terephthalate) above the glass transition. Polymer, 2183-2201. Boyce, M. C., Parks, D. M. & Argon, A. S., 1988. Large inelastic deformation of glassy polymers. part I: rate dependent constitutive model. Mechanics of Materials, 15-33. Boyce, M. C., Weber, G. G. & Parks, D. M., 1989. On the kinematics of finite strain plasticity. Journal of the Mechanics and Physics of Solids, 647-665. CES EduPack software, Granta Design Limited, Cambridge, UK, 2009. Cho, H. & Boyce, M. C., 2015. Constitutive modeling of high strain-rate elastomeric polymers. In: Elastomeric polymers with high rate sensitivity. Elsevier, 115-183. Choi, T., Roland, C. M., Fragiadakis, D. & Runt, J., 2012. Microstructure and segmental dynamics of polyurea under uniaxial deformation. Macromolecules, 3581-3589. Corran, R., Shadbolt, P. J. & Ruiz, C., 1983. Impact loading of plates - an experimental investigation. International Journal of Impact Engineering, 3-22. Johnson, G. R. & Cook, W. H., 1985. Fracture characteristics of three metals subjected to various strains, strain rates, temperatures and pressures. Engineering Fracture Mechanics, 21, 31-48. Lesuer, D. R., LeBlanc, M. M. & Kay, G. J., 2001. Modeling large-strain, high-rate deformation in metals. The Minerals, Metals & Materials Society. Marom , I. & Bonder, B. R., 1979. Projectile perforation of multi-layered beams. International Journal of Mechanical Sciences, 21, 489-504. Pangon, A., Dillon, G. P. & Runt, J., 214. Influence of mixed soft segments on microphase separation of polyurea elastomers. Polymer, 55, 1837 1844. Acknowledgements The reported study was partially supported by the Government of Perm Krai, research project No. C-26/790 from 21.12.2017 References