Vibration and Energy Dissipation of Nanocomposite Laminates for Below Ballistic Impact Loading

Abstract Composite laminates are made of glass woven roving mats of 610gsm, epoxy resin and nano clay which are subjected to projectile impact. Nano clay dispersion is varied from 1% to 5%. Impact tests are conducted in a gas gun setup with a spherical nose cylindrical projectile of diameter 9.5 mm of mass 7.6 g. The energy absorbed by the laminates when subjected to impact loading is studied, the velocity range is below ballistic limit. The effect of nano clay on energy absorption in vibration, delamination and matrix crack is studied for different weight % of nano clay and for different thickness values of the laminates. The natural frequencies and damping factors are obtained for the laminates during impact and the effect of nano clay is studied. The results show considerable improvement in energy absorption due to the presence of nano cla

Modal analysis of pre and post impacted nano composite laminates

Modal analysis is carried out on pre and post impacted nano composite laminates. The laminates are prepared using 3, 5 and 8 layers of 610gsm glass woven roving mats(WRM) with epoxy resin and montmorillonite(MMT) clay content is varied from 1% to 5%. Impulse hammer technique is used to find natural frequency and damping factor of laminates. Medium velocity impact tests are conducted by using a gas gun. The vibration responses of natural frequency and damping factor are obtained and are studied for laminates with all edges clamped boundary conditions. Results show considerable improvement in natural frequency and damping factor due to nano clay addition. It is also seen that the nano clay controls the delamination due to impact loading

Pulsed Laser Assisted Micro-Scribing of Metal thin Films in Air and Underwater Using UV, Visible and Near-IR Wavelengths

AbstractA comparative study has been made for micro-scribing of copper and aluminum thin films in air and underwater using 355nm, 532nm and 1064nm wavelengths of a Q-switched Nd3+: YAG laser with 6ns pulse duration. For aluminum in air medium, the channel depth obtained is high for 355nm wavelength, whereas for copper coated on a polyimide substrate, 532nm wavelengths produced higher depth. In underwater scribing, with increase in the pulsed laser energy, the depth of micro channel was increased and remained unchanged at higher energy. The influence of beam profile on the micro channel cross-section has also been discussed. Further, theoretical modeling of the laser-material interaction in air and underwater ambience conditions to estimate the recession rate has been discussed by incorporating the laser ablation temperature measured using the laser induced breakdown spectroscopy technique

Identification of antifungal compounds from the seed oil of Azadirachta Indica

Evaluation of the activity of the cold expeller neem oil (Azadirachta indica A. Juss.) and the fractions derived through solvent partitioning, against Drechslera oryzae, Fusarium oxysporum and Alternaria tenuis showed that the active antifungal fraction is a mixture of tetranortriterpenoids. Further, testing the triterpenoidal mixture derived from the 90% methanol (MeOH) extract of neem oil against 13 phytopathogenic fungi revealed that various species were inhibited to different degrees. Direct preparative High Performance Liquid Chromatography (HPLC) of the active fractions and subsequent bioassay of the semi-pure fractions indicated that the active fractions contained major compounds such as 6-deacetylnimbin, azadiradione, nimbin, salannin and epoxyazadiradione. Pure azadiradione, nimbin, salannin and epoxy-azadiradione did not have appreciable activity. However, when these terpenoids were mixed and bioassayed, they showed antifungal activity, indicating possible additive/synergistic effects