Opportunities in Protection Materials Science and Technology for Future Army Applications (2011) / Chapter Skim
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3 Mechanisms of Penetration in Protective Materials
3 Mechanisms of Penetration in Protective Materials
Pages 24-34
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From page 24... ...
In situ, et al., ballistic tests often show that the best-performing armor material is not necessarily the strongest, the toughest, or the hardest. Are there other properties that reliably offer BOX 3-1 guidance in choosing and developing armor materials, if such Microstructural Options for Influencing Failure conventional bulk properties do not?
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the crater in a 1-in.-thick steel plate that has been impacted at 6 km/s by a 12.7-mm-diameter polycarbonate sphere.2,3 Partially penetrated targets are particularly useful for Adiabatic4 shear bands can be seen as white-etching bands determining failure mechanisms. A close examination of areas where the damaged material remains in place and of of hard, untempered martensite extending into the plate (1)
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From page 26... ...
Such tests produce ring cracks and radial cracks on the impacted surfaces, as well as the well-known Hertzian cone cracks, which extend into the target at divergent angles from the shot line. More important when considering penetration mechanisms, however, is the microdamage produced in the target directly ahead of the projectile, since it is the material in this location that must FIGURE 3-3 Polished cross sections through the shot line of a SiC be extruded from the projectile path to permit penetration.
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1990. Failure phenomenol process is obtained by examining cross sections of partially ogy of confined ceramic targets and impacting rods.
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Third, mechanism route to better armor materials. International Journal of Applied Ceramic Technology 7(5)
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In- Fiber failure modes other than tensile failure are also obternational Journal of Applied Ceramic Technology 7(5)
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2004. Lightweight Ballistic Protection of Flight-Critical Components on Commercial Aircraft, Part 2: Large-Scale Ballistic Impact Tests and Computational Simulations, DOT/FAA/AR-04/45,P2.
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2000. Experimental analysis of deformation mechanisms in a closed-cell aluminum alloy foam.
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Cellular materials absorb blast energy by deforming fracture bands similar to the deformation bands in formation and failure of cell walls. ductile aluminum (Figure 3-12)
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Such tests must be conducted under well-controlled and moni tored conditions of load, rate, and temperature and need to measure the governing (nonconventional) material failure properties; • Performing other tests in which the load application is stopped at various percentages of the maximum load and the specimens sectioned and examined microscopically to observe the damage at increas ing stages of development and the interaction of the damage with microstructural features; • Prescribing microstructures that repress or interfere with failure mechanisms and interacting with proFIGURE 3-13 SEM images of failed cells in brittle aluminum foam cessing engineers to innovate ways to achieve these showing failure modes (a)
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From page 34... ...
• Choose materials based on their ability to inhibit or avoid material failure mechanisms, as opposed to choosing materials based on their bulk properties.
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