Abstract
Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene–acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3 m sized panels were subjected to blast of a Hopkinson–Cranz scaled distance of 3.02 m kg−1/3, 100 kg TNT equivalent at a stand-off distance of 14 m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411–413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast.
Highlights
The recent advances in composite manufacturing have occurred predominantly in the aerospace, marine, automotive and related industries
Some early research was performed on this by Caprino & Teti [22], where glass-fibre skin–polyvinyl chloride (PVC) core sandwich panels were subjected to impact on a drop tower, and their residual strength determined with tensile testing
It was shown that during the blast the carbon-fibrereinforced polymer (CFRP)-skinned sandwich panels provided a greater resistance to the blast-wave impact, deflecting to a lower Uzmax compared with the Glass-fibre-reinforced polymer (GFRP)-skinned target
Summary
The recent advances in composite manufacturing have occurred predominantly in the aerospace, marine, automotive and related industries. Some early research was performed on this by Caprino & Teti [22], where glass-fibre skin–polyvinyl chloride (PVC) core sandwich panels were subjected to impact on a drop tower, and their residual strength determined with tensile testing. Bull & Edgren [23] performed residual strength testing on carbon-fibre skin–PVC core sandwich panels, which had been subjected to impact loading on a drop tower. With the FEA model set up in this way, strong agreement was found with experimental results for panel response in edgewise compression and the onset of dent growth [24] This approach is similar to that used in this research, in which damage is generated in the FEA geometry from the start, in order to determine the residual strength with this damage in place. Criteria for damage assessment of service life are investigated, with the view of damage mapping models being generated to enable the assessment of continued service applied to naval vessels subjected to blast
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