PSI - Issue 14

3

Aisha Ahmed et al. / Procedia Structural Integrity 14 (2019) 507–513 Aisha Ahmed/ Structural Integrity Procedia 00 (2018) 000–000

509

Therefore, an ideal confinement of ceramic should:  Ensure the position of front plate in place,  Confer integrity of the front (ceramic) plate,  Build strong bond with ceramic,  Increase the dwell time  Prevent passage of secondary projectiles

This study has been focused on developing a suitable polymeric system for the better confinement of ceramic based on dynamic mechanical properties, being characterized at high strain rates (10 3 to 10 5 /s) using split Hopkinson pressure bar. 2. Experimental Work 2.1. Split Hopkinson Pressure Bar (SHPB) Test To govern the compressive mechanical behaviour of materials at high strain rate loading conditions split Hopkinson pressure bar (SHPB) was employed which was in-house fabricated, calibrated and operated as published in the literature by Asija et al. (2017). The various assumptions taken as the prerequisites, theory, instrumentation and methodology of SHPB which were well explained in the literature by Song and Chen (2005). The schematic of SHPB setup is shown in the Fig 1.

Fig. 1. Schematic of Split Hopkinson Pressure bar setup

SHPB setup works on the principle of one-dimensional stress wave propagation. When the striker bar hits the incident bar pressure wave traverse through the incident bar and enters the specimen. A part of the wave is reflected to the incident bar and rest of it is transmitted to the transmission bar depending upon the acoustic impedance mismatch of bar and specimen material. The incident and reflected wave were recorded by the strain gauge mounted at the incident bar and the transmitted wave were recorded by strain gauge mounted at transmitted bar in the form of voltage signals. The following three analytical relation were used to calculate the average stress, average strain and strain rate with respect to time using voltage signals recorded by the two strain gauges.

Average stress , ( ) t 

( )

b E A t A  t

 

(1)

s

( 2 ) ( ) o C t L  r

s 



(2)

Average strain ,

s