PSI - Issue 60

Prince Jeya Lal Lazar et al. / Procedia Structural Integrity 60 (2024) 185–194 Author name / Structural Integrity Procedia 00 (2019) 000–000

187

3

Fig. 1 Air blast shock-wave pressure-time history [8]

2.2. Underwater Explosion This work incorporated the previously established empirical relations of UNDEX blast wave propagation. Equation 3 presents an exponentially decaying blast wave for a given charge mass and standoff distance [7]. ( ) = ( $"- ).exp2 ((#(# " + ) 4 (3) The induced cavitation in a fluid medium because of a UNDEX event generates nonlinear behavior at fluid structure interaction and is incorporated in the present work by Taylor's theory. The modified pressure field in the reflected regime and the velocity of the sandwich panel can be estimated by Taylor’s plate theory. Shock factor (SF) as a function of explosive mass, standoff distance angle of incident explosion, etc. may be used to characterize an underwater explosion. SF is defined in Equation 2 by [8]. A typical simulation of an underwater explosion is presented in Fig. 2. = 2 √ 0 / 4 2 (1,2 5 3'4) 4 (4)

t = 0 ms

t = 1.0 ms

t = 1.5 ms

Fig. 2 A typical underwater explosion simulated through the UNDEX algorithm using Abaqus Explicit at various time frames

3. Sandwich panel geometry, materials, and mesh validation The structural geometry of the sandwich panels used in the present simulation was referred to in [19]. Square honeycomb panels of size 610 mm, with a core height of 51 mm and a face plate of 5 mm thick were used in this work. The relative density of the square honeycomb core was designed to be 5-10% by varying the core thickness in