Optimization of two-component composite armor against ballistic impact
Using Florence's model we determined an optimal design of a two-component ceramic-faced lightweight armor against normal ballistic impact. The solution is found in a closed form that allowed us to determine the thicknesses of the plates in the optimal armor as functions of the specified areal density of the armor, parameters determining the material properties of the armor's components and characteristics of the impactor.
Effect of design on the performance of steel-alumina bilayers and trilayers subject to ballistic impact
© 2015 Elsevier Ltd. All rights reserved. Composite armors systems containing ceramic components are capable of offering greater ballistic protection than those of monolithic metals alone. The level of protection afforded by a composite armor depends sensitively on the materials utilized and their spatial configuration. Using numerical simulation, we investigate the effects of relevant design parameters on the ballistic performance of thin, unbonded ceramic-metal bilayers and trilayers subject to normal impact by steel spheres. The deformation behavior of the constituent phases is described by established constitutive laws. The predictive capability of the numerical model is validated through comparisons of simulation results with experimental measurements of displacement profiles of the back facesheet of a reference trilayer. The simulation results indicate that the ceramic-metal bilayer with the ceramic at the impact side offers the highest ballistic resistance; removing metal from the rear of the structure and placing it on the impact side (forming a trilayer) results in reduced ballistic resistance. Additionally, the onset of target penetration is found to correlate with high levels of energy dissipated within the target. The implication is that composite armors should be designed to maximize the energy dissipated in the projectile, not in the armor. Accordingly, effective designs at resisting failure are found to have high ceramic-to-metal mass ratios, with a finite (though small) amount of metal on the back face.
Palm oil shell aggregate for lightweight concrete
Publisher Summary Increased agricultural production and the development of agro-based industries in many countries of the world have brought about the production of large quantities of agricultural wastes, most of which are not adequately managed and utilized. Low-cost building materials can be produced using inexpensive indigenous raw materials. Agricultural wastes that are renewable and are found in abundance in many countries present an interesting alternative to the traditional and sometimes imported building materials, particularly for low-cost construction. The use of agricultural wastes as aggregates in lightweight concrete can provides an alternative to conventional methods for the production of lightweight concrete. Lightweight concrete results in a reduction in the overall deadweight of a structure and provides a significant saving in the overall cost of construction. The use of less expensive alternative lightweight aggregates in the production of the concrete can provide further reductions in expense. The material properties and structural performance of lightweight concrete with palm oil shells as aggregates are similar to lightweight concrete produced using the more common lightweight aggregates such as clinker, foamed slag, and expanded clay. The palm oil shells are hard and are received as crushed pieces because of the process used to release the oil. Manual sieving is necessary to remove the large amount of fine particles. The shells are then air-dried before use. Because the palm oil shells are lighter than the cement matrix, the shells tend to segregate in wet concrete mixes. On the other hand, dry mixes using palm oil shells are relatively more difficult to work with when compared to ordinary concrete. Trial mixes are necessary to achieve a good mix design.