E t	Energy absorbed during impact
E p	Energy consumed in plug formation
E 1	Energy absorbed by 1st/front layer at impact point that results in erosion or perforation
E 2	Energy absorbed in radial stretching of target plate at front end
E 3	energy absorbed by 2nd/back layer of composite structure
${\rho }_{\mathrm{b}}$	density of bullet
${\rho }_{\mathrm{fl}}$	density of target front layer
${\rho }_{\mathrm{bl}}$	density of target back layer
$h_{\mathrm{fl}}$	thickness of target (front layer)
$h_{\mathrm{bl}}$	thickness of target (back layer)
$A_{\mathrm{b}}$	cross-sectional area of bullet
$r_{\mathrm{b}}$	radius of bullet
$Y_{\mathrm{t}}$	yield strength of target plate (front layer)
$v_{\mathrm{i}}$	initial velocity of bullet
$v_{\mathrm{bl}}$	ballistic limit velocity
$v_{\mathrm{r}}$	residual velocity of bullet
$l_{\mathrm{n}}$	nose length of bullet
$w_{\mathrm{c}}$	plate deflection
$\mu$	Poisson ratio
$h_{\mathrm{b}}$	thickness of bullet
$m_{\mathrm{b}}$	mass of bullet
$m_{\mathrm{br}}$	mass of bullet at the time it encounters 2nd layer of composite structure
$C_{\mathrm{de}}$	depth of crater
$\mathrm{a}$	crater profile
$x$	radius of dent on back layer
$\beta$	deformation parameter based on stress and strain