Ceramic mosaics have been used in lightweight armor systems to gain additional multi-hit capacity. However, the tile-to-tile interfaces in ceramic mosaics are inherently vulnerable and thus require special attention. In this research, we present finite element analysis of bilayer armor systems that consist of a ceramic mosaic front layer and a Kevlar-29/epoxy composite backing layer. The objective was to investigate the effect of various tile-to-tile interface designs on the ballistic performance. Two different interface design philosophies are investigated. In the first design, adjacent ceramic tiles are bonded together using epoxy at the interface, considered as a gap filling material. In the second design, adjacent ceramic tiles are separated by metallic webs at the interface, where a titanium honeycomb structure has ceramic tiles inserted into it. The same thickness was imposed for each interface wall to enable a direct comparison of their impact behaviour. Impact location was designated as the central ceramic tile centre. It was found that different interface designs affect stress wave propagation in the armor due to impedance mismatch. The stress state induced in the ceramic tile can be drastically changed and therefore the ballistic resistance of the armor. These results can be used to for the tailoring of mosaic armor systems to achieve the best ballistic performance.
This study focused on the design, modelling and the analysis of the dynamic response of sandwich composite armor system, constructed with kevlar 29/phenolic matrix, carbon fiber/epoxy (T300 6k/ Epon 862) and carbon fiber/epoxy (T300 6k/ Epon 862, with 4% carbon nanotube) as top and bottom skins. The core of the sandwich composite armor was made of triangular corrugated aluminum structure filled with prismatic silicon carbide. The triangular corrugated core was used to change the direction of bullet. The skin thickness, material composition, impact velocity etc., was varied to get their influence on the impact resistance of the armor system. The sandwich structure typically consisted of front plate, core and backing plate, which was impacted at different velocities starting at 1400 m/s to 1700 m/s, where complete armor penetration was noticed. From the dynamic analysis, the residual velocity and energy absorption capacity were obtained and the energy absorption capacity for various configurations were compared. The results of all models with 2mm, 3mm and 4mm skin thickness revealed increased energy absorption of the sandwich armors with carbon fiber/epoxy (T300 6k/ Epon 862, with 4% carbon nanotube) as skins and with kevlar 29/phenolic matrix as skins the sandwich armor yielded the least energy absorption. The sandwich composite armor model used in this research was unique in-terms of skin composition, combination of materials, geometry and assembly. Due to limitations of manufacturing and testing facilities of the sandwich composite armor, a kevlar/epoxy laminate finite element model was validated with the experimental test results found in the literature. The deviation of the results was noticed, and the reasons of deviation were discussed.
The main objective of this research is to find a system capable of treating urban wastewater, both in terms of physico-chemical and bacteriological quality. The composite material made from clay and particles of TiO2 appears to be effective in eliminating pollution from urban wastewater: case of the Marais Masay lake. Physicochemical analysis (pH, conductivity, MES, turbidity, nitrate, phosphate and chloride levels, COD, BOD) and bacteriological analysis (ASR, fecal coliforms, fecal streptococci and Escherichia Coli) have made it possible to assess the quality of treated waters. The model reduced the amount of physicochemical pollution of wastewater at the end of the treatment. The pH is between 6 and 9, the conductivity is reduced, it goes from 429.33 to 273 μS/cm, the turbidity is 17.8 NTU, the SS varies from 12.5 mg/l. Nitrite and phosphate levels are 0 mg/l. The COD is less than 50 mg/l, the BOD is less than 150 mg/l all values meet the release standard. Based on these results, 99.78% of Streptococci fecal germs, 99.64% of ASR, 97.84% fecal coliforms, 98.43% Escherichia Coli package are eliminated. Microbiological and physico-chemical reveal that the treated waters are qualitatively improved.
The effect of the oil shale ash (OSA) addition on the impact, tensile, flexural, water uptake, and morphological behavior of the chlorinated polyvinylchloride (CPVC) was investigated. Adding OSA filler to CPVC matrix yielded a greater impact strength of 498 kJ/m2. While the tensile stress at yield and at break increased by an average of 50% and 100%, respectively, the tensile strain at yield and at break increased by an average of 20% and 10%, sequentially. The tensile and flexural modulus of OSA/CPVC increased by 16% and 65%, respectively. The results of this work demonstrated that the OSA could be used as a reinforcement material for the CPVC polymer, providing superior mechanical properties with respect to the neat polymer, as long as an appropriate OSA filler proportion, 5% - 15-%, is included into the CPVC polymer composite. Water absorption was increased with the increase of the OSA filler content. Scanning electron microscopy microphotographs evidenced the improvement in the mechanical behavior of the OSA/CPVC polymer composite by low level of both filler pullout and voids.
