Blast Loading of Sandwich Structures and Composite Tubes

Abstract

This chapter reviews blast impact experimentation on glass fibre reinforced polymer (GFRP) and carbon-fibre reinforced polymer (CFRP) sandwich composite materials and laminate composite tubes. Explosive charges of 0.64–100 kg TNT equivalent were used during these air- and underwater-blast tests. The difference in response and damage inflicted from underwater- and air-blast loading was assessed from strain-field measurements and post-blast specimen analysis. Procedures for monitoring the structural response of such materials during blast events have been devised. High-speed photography was employed during the air-blast loading of GFRP and CFRP sandwich panels, in conjunction with digital image correlation (DIC), to monitor the deformation of these structures under shock loading. Failure mechanisms have been revealed using DIC and confirmed in post-test sectioning. The improved performance of composite sandwich structures with CFRP skins compared to GFRP equivalent constructions is demonstrated for air-blast experiments. Strain gauges were used to monitor the structural response of similar sandwich materials and GFRP tubular laminates during underwater shocks. The effect of the supporting/backing medium (air or water) of the target facing the shock has been identified during these studies. Mechanisms of failure have been established such as core crushing, skin/core cracking, delamination and fibre breakage. Strain gauge data supported the mechanisms for such damage. A transition in behaviour was observed in the sandwich panels when subject to an underwater blast as opposed to an air-blast load. Damage mechanisms notably shifted from distributed core shear failure originating from regions of high shear in air blast to global core crushing in underwater blast. The full-scale experimental results presented here will assist in the development of analytical and computational models. Furthermore, the research highlights the importance of boundary conditions with regards to blast resistant design.