The
effects of high-pressure shock waves generated by the detonation
of explosives are of major interest to the strategic sector. We report
interaction of transonic shock waves (1.1 Mach speed; peak pressure
>1.5 GPa) with graphene-like nanoflakes (GNFs). GNF samples, obtained
after chemical vapor deposition of a biomass, were studied using optical/electron,
force microscopy, Raman, and Brunauer–Emmett–Teller/Barrett–Joyner–Halenda
studies. Following this, GNF samples were subjected to high-strain-rate
measurements, using a split Hopkinson pressure bar technique to measure
variations in the stress, strain, and strain rate. Numerous dynamic
mechanical parameters are derived under a classical Lagrange–Rankian–Hugoniot
framework together with collecting statistics on the lateral flake
size, number of layers, defect density, wrinkle, slip characteristics,
etc. Broadly, the incident shock energy was dampened by ∼65%
of absorption loss with ∼15% transmittance. It has implications
on the GNF microstructure by reducing the flake squareness, area (by
∼50%), and exfoliating layer conjugation by around 5 times.
The in-plane impact was more profound compared to the out-of-plane.
Dislocation/slip dynamics showed significant modification in prismatic
loops (from buckled to ruck and tuck), with twinning exhibiting a
lowering of the Peierls–Nabarro stress to make disorder glissile.
At the molecular level, dynamic deformation dramatically modified
the force constants with bond elongation at −C–C–
by ∼80% and at −CC– by >150% compared
to pristine. An interactive model is presented.
In addition to high pressure generated by explosion, the induced high acceleration can also cause severe injuries to occupants and structural damage, especially in anti-vehicular land mine blast scenario. This problem has not been studied well and only few techniques to reduce the deadly effect of high acceleration are reported in literature. In the present work, the mitigation of blast induced acceleration using add-on layers of open cell natural rubber and synthetic foam on rigidly fixed composite plate has been studied experimentally under increasing blast wave strengths. The blast wave strength was varied by increasing quantity of plastic explosive from 0.150 kg to 0.550 kg. The induced vibration in the composite plate due to impingement of blast wave was measured in terms of acceleration using piezoelectric accelerometer. It was observed that the sharp rising acceleration signals were transformed into a slowly rising and low amplitude signals with the addition of foam. The mitigation of high frequencies and amplitude of acceleration signals was also verified with the fast Fourier transform study. The rubber foam shows better acceleration mitigation than synthetic foam. This study has suggested that the material like rubber and synthetic foam can be used for mitigating the acceleration resulting from the impact of blast wave.
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