Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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2005 - 200912010 - 20181

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Subject: search.filters.subject.Ballistic impact

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  • Master Thesis
    The Effect of Material Strain Rate Sensitivity on the Shock Deformation of an Aluminum Corrugated Core
    (Izmir Institute of Technology, 2018) Canbaz, İlker; Güden, Mustafa; Taşdemirci, Alper
    The effect of the material model on the crushing behavior of a layered 1050 H14 aluminum corrugated sandwich structure was investigated numerically as function of velocity (0.0048, 20, 60, 150 and 250 m s-1) using three different material models; elastic-perfectly plastic (model I), elastic-strain hardening (model II) and elastic-strain and strain rate hardening (model III). Three-dimensional finite element models were developed in the explicit finite element code of LS-DYNA. Between 0.0048 m s-1 and 20 m s-1, the numerically calculated stresses at the impact and distal end were almost the same and in equilibrium, showing a “quasi-static homogenous mode”. The deformation mode at 60 m s-1 was a “transition mode” and between 150 and 250 m s-1 a shock mode in which the layers were crushed sequentially. The numerical study showed that the strain and strain rate hardening models tended to induce non-sequential layer crushing. The collective layer crushing was also more pronounced in the material model II and III than the material model I. For low strain hardening aluminum alloys and similar materials, the effect of strain hardening in increasing plateau stress was more significant than the strain rate hardening at the quasi-static velocity, while both strain hardening and strain rate hardening effect increased with increasing velocity. The stress reduction by the inclusion of imperfections however declined with the velocity since the samples started to deform near the impact end as the velocity increased.
  • Master Thesis
    Development and Characterization of Light-Weight Armor Materials
    (Izmir Institute of Technology, 2005) Ünaler, Erol; Tanoğlu, Metin
    In this study, E-glass/unsaturated polyester composite laminates using woven and non-crimp stitched fabrics and isophtalic and orthophthalic polyester resin were fabricated using RTM (Resin Transfer Molding) technique. In addition to composite laminates, multilayered sandwich laminates using aluminum (Al) plates and alumina (Al2O3) tiles were manufactured to improve the ballistic resistance of the composite structure. An experimental investigation was carried out to determine the mechanical and ballistic performance of E-glass/unsaturated polyester composite laminates with and without aluminum and alumina tiles. The mechanical properties of the composite laminates made with 0/90 woven fabrics and 0/90 and 0/-45/+45/90 non-crimp stitched fabrics and two resin systems were measured for comparison of fabric and resin types. The flexural strength and modulus, compressive strength and modulus through ply-lay up and in plane loading directions, mode I interlaminar fracture toughness and apparent interlaminar shear strength of the composites were measured to evaluate the effects of the fiber architecture on the mechanical properties of the composites. It was found that in general the mechanical properties of the composites made with 0/90 woven fabrics are higher than those of the composites made with multiaxial non-crimp stitched fabrics. Moreover, the composite plates with and without aluminum plates and alumina tiles were subjected to ballistic impact by AP (armor piercing), FSP (fragment simulating projectile) and ball (B) type projectiles with initial velocities in the range of 420-1173 m/s. The ballistic test results exhibit that the polymer composites have ballistic resistance against 7.62 mm fragment simulating projectiles (FSP) up to 1001 m/s projectile velocities. However, the composites without any support layer are not sufficient to stop AP projectiles. The sandwich panels containing ceramic tiles subjected to the ballistic impact by AP and FSP projectiles exhibited only partial penetrations at all the velocities applied within the study (446-1020 m/s with AP and 435-1173 m/s with FSP). The extensions of damages in the composites were evaluated after impact. It is concluded that the multilayered composite structures have capacity against the ballistic threats and potential to be used as lightweight armor materials.