Ballistic Impact Behaviour of Glass/Epoxy Composite Laminates Embedded with Shape Memory Alloy (SMA) Wires

This paper aims to estimate the enhancement in the energy absorption characteristics of the glass fiber reinforced composites (GFRP) by embedding prestrained pseudo-elastic shape memory alloy (SMA) that was used as a secondary reinforcement. The pseudo-elastic SMA (PE-SMA) embedded were in the form of wires and have an equiatomic composition (i.e., 50%–50%) of nickel (Ni) and titanium (Ti). These specimens are fabricated using a vacuum-assisted resin infusion process. The estimation is done for the GFRP and SMA/GFRP specimens at four different impact velocities (65, 75, 85, and 103 m/s) using a gas-gun impact set-up. At all different impact velocities, the failure modes change as we switch from GFRP to SMA/GFRP specimen. In the SMA/GFRP specimen, the failure mode changed from delamination in the primary region to SMA-pull out and SMA deformation. This leads to an increase in the ballistic limit. It is observed that energy absorbed by SMA/GFRP specimens is higher than the GFRP specimens subjected to the same levels of impact energy. To understand the damping capabilities of SMA embedment, vibration signals are captured, and the damping ratio is calculated. SMA dampens the vibrations imparted by the projectile to the specimen. The damping ratio of the SMA/GFRP specimens is higher than the GFRP specimens. The damping effect is more prominent below the ballistic limit when the projectile got rebounded (65 m/s).     

Benzene thermal synthesis and characterization of crystalline carbon nitride

A new solvothermal route has been successfully used to prepare crystalline carbon nitride powder from 1,3,5-trichlorotriazine (C₃N₃Cl₃) and lithium nitride (Li₃N) in benzene at 360 °C and 6–7 MPa. The as-prepared sample was brown and was analyzed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The results show that the powder mainly consists of -C₃N₄, -C₃N₄ and some unidentified carbon-nitrogen crystalline phases. The experimental lattice constants of -C₃N₄ (a=6.48 Å,c=4.72 Å) and -C₃N₄ (a=6.43 Å,c=2.47 Å) match the latest ab-initio calculations (a=6.47 Å and c=4.72 Å for -C₃N₄, a=6.40 Å and c=2.40 Å for -C₃N₄) quite well. The relative nitrogen-to-carbon composition ratio is 0.76. Only C–N and C=N bonds were demonstrated by XPS and FTIR. The feasibility of this synthetic method is discussed and this approach may provide a possible and very effective way to realize the growth of pure crystalline carbon nitride materials, which is quite different from the conventional solid-state reactions (SSR). PACS 81.10.-h; 81.10.Dn; 81.05.Zx; 61.66.Fn; 42.70.Nq