A Test of the Acoustic Impedance Model of Blast Wave Transmission

The ability of armour to minimize blast wave transmission is key in mitigating blast-related injuries. The acoustic impedance model is commonly employed to estimate blast wave transmission of candidate armour materials even though the model assumes semi-infinite material thickness. The applicability of the acoustic impedance model to blast wave transmission through plates has not been experimentally verified. In this study, a 79 mm diameter, oxyacetylene driven shock tube was used to generate a blast-like wave with a peak pressure of 1173 kPa. The pressure wave transmitted through 6.35 mm thick plates of ten different materials spanning a range of acoustic impedances was measured and compared with predictions of the acoustic impedance model. The magnitude of the peak transmitted blast pressure averaged over five trials for each material was well correlated with both the acoustic impedance of the material (correlation coefficient, r = -0.709) and with the predicted peak transmitted blast pressure (r = 0.844). However, in all cases, the acoustic impedance model predicted significantly lower peak blast pressure transmission than was actually observed, with the peak transmitted pressure varying from 9 to 90 times greater than the prediction of the model, with an average transmission of 41 times the prediction of the model. These results show that even though plate materials with higher acoustic impedance tend to transmit lower peak blast pressure, transmitted pressures are much higher than model predictions, and increasing the acoustic impedance does not ensure a decrease in peak transmitted blast pressure when selecting armour materials.