This paper present the study about the mechanical properties of two high strength low alloy steels for replacing the current rolled homogeneous armour (RHA) for ballistic application. High strength low alloy steel has been widely adapted as a ballistic plate in light armoured vehicle. However, the current used RHA plate is very heavy thus restricted the manoeuvrability of the armoured vehicle. The aim of this study is to find materials suitable to be used for production of composite protection panel which is lighter yet has similar mechanical properties to RHA. The tensile strength and hardness of AISI 4340 and AR500 steels were evaluated and compared to that of RHA and the results were analysed based on its chemical compositions and microstructural observation. Values of these properties are primarily reflected by its microstructures and chemical compositions. Therefore, microscopic observation of microstructural arrangement and phases are essential in understanding the hardness and stress-strain behaviour of these metals. Results indicate similar tensile properties were observed in RHA and AR500 but different properties obtained for AISI 4340. Tensile strength of RHA and AR500 were 1750 MPa and 1740 MPa respectively followed by AISI 4340 at 1020 MPa. AISI 4340 steel exhibited the highest elongation at 20.6% compared to RHA and AR500 at 13.3 and 12.5%, respectively. Higher degree of carbon content in fine martensitic structure of RHA and AR500 led to high hardness. Imperfections in RHA and AR500 were also removed by hot rolling process as indicated by white banding that cause higher in tensile strength. Retained austenite and coarse microstructure of AISI 4340 steel contributed to higher ductility compared to AR500 and RHA. Therefore the tensile properties of RHA and AR500 were found similar due to its microstructure behaviour. This similarity allows AR500 to be utilised as alternatives to RHA in armour plate application.

This paper presents the ballistic performance of the joining lightweight metal laminated panel consists of high strength steel and aluminium alloy for armoured vehicle application. Composite laminates trend in military industry present excellent performance in terms of lightweight material due to the improvement vehicle manoeuvrability, without sacrificing the performance and safety. The combination of   aluminium plate and high strength steel offer the good potential for reducing the vehicle weight and improving the ballistic resistance. Ar500 and Al7075-T6 were chosen in designing laminated panel to achieve intended 20-30% weight reduction. Joining between these two materials have been investigated using both brazing method and adhesive bonding method. The adhesive bonding involved two types of material which is epoxy and polyurethane. Mechanical tests such as bending tests, drop weight tests and ballistic tests were performed to assess the strength of the laminated panel. Results showed that polyurethane bonded laminate panel through adhesion process exhibited 75% higher strength that that through the brazing process after performing impact test. Meanwhile, the penetration patterns found numerically are nearly similar to that from the ballistic tests and thus has validated the finite element models developed. The study on application of this laminated plate shall be extended using higher level of threat for hard armour vehicle panel.

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Purpose: To evaluate the effect of three natural materials (Ginger and honey mixture and rosemary oil) on remineralization and prevention of enamel white spot lesions measured by color change using vita easy shade. Material and methods: The study was carried out in two phases remineralization and prevention phase, sixty four anterior teeth were used for each phase. Teeth were prepared and randomized into four groups according to treatment material (n=8 samples). Group I: control group which receives no treatment. Group II: treated with 1.23% sodium fluoride gel. Group III: treated with ginger-honey mixture. Group IV: treated with rosemary oil. Treatment material was applied for 3 or 6 minutes. In phase (1) color was measured at baseline, after creation of white spot lesion, and after treatment. In phase (2) color was measured at baseline and after treatment. Data were obtained and the differences between groups were estimated by ANOVA test followed by Tukey's post hoc test. Results: for phase1:There was a statistically significant difference among different groups. The highest mean value of ΔE was for sodium fluoride gel group followed by ginger and honey group at 6 min. For phase2: group III had a better acid resistance effect followed by group II at 6 min. Conclusion: Natural materials can be used for remineralization and prevention of WSL as ginger and honey mixture enhance remineralization following sodium fluoride gel which was more effective. And for acid resistance phase, ginger and honey mixture was more effective.

Background.A variety of natural and synthetic agents have recently been used in clinical trials to arrest dentin caries.Objectives. The aim of the present study was to explore the remineralization and antibacterial effect of natural (propolis, hesperidin) vs. synthetic (silver diamine fluoride (SDF)) agents on deep carious dentin. Material and methods.A total of 64 human molar teeth with Class I caries were randomly distributed into 4 groups: control group; propolis group; hesperidin group; and SDF group. The cavities were prepared using the stepwise caries removal technique, and then covered with the materials to be tested. The samples were taken from the carious lesions before and after treatment to evaluate the antibacterial effect. Then, the teeth were restored with a glass ionomer cement (GIC). Digital X-rays were taken to assess remineralization and the antibacterial effect after 6 and 12 weeks.Results. The highest value of radiodensity was observed in the propolis group (46.44 ±9.65 HU), while the lowest value was noted in the hesperidin group (12.62 ±5.86 HU). The bacterial count in the propolis group was 1,280.00 ±1,480.54 CFU/mL at baseline, which was not significantly higher than the value measured after 6 weeks (574.00 ±642.48 CFU/mL; p = 0.153), whereas in the hesperidin group, the mean value of the bacterial count at baseline (3,166.67 ±1,940.79) was not much higher as compared to the value obtained at 6 weeks (2,983.33 ±1,705.77) (p = 0.150). Conclusions.In comparison with SDF, propolis and hesperidin agents showed promising effects in terms of remineralization of carious dental tissue and hindering the progression of caries.