Compressive strength after blast of sandwich composite materials

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.1914.000810.1098/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.

Sandwich Panel Cores for Blast Applications: Materials and Graded Density

“…The sandwich panel has been sectioned into just 16 parts, to give a purely comparitive estimate of damage suffered between the sandwich panels. The panel has been split such to allow for postblast strength assessments to be performed on the sandwich panels, similar to the research performed by Arora et al [22].…”

Compressive response of sandwich plates to water-based impulsive loading

“…Projectile impact velocities in the range of 15-150 ms -1 are used to delineate the effect of loading rate on the deformation and failure behavior of the structures analyzed. This velocity range corresponds to peak pressures between 15 and 200 MPa, which are comparable to pressures observed in underwater explosions [17][18][19]. The metal platens have a thickness of 10 mm and a diameter of 100 mm; while the foam specimens have a thickness of 50 mm and a diameter of 70 mm Figure 2 A schematic illustration of the dynamic compression "Dynacomp" test setup within the Underwater Shock Loading Simulator (USLS).…”

“…Additionally, the forces and impulses transmitted by sandwich structures are significantly smaller than those transmitted by monolithic structures [9][10][11]. Recent assessments of blast-loaded marine structures show that fluid structure interaction (FSI) effects play an important role in response and can be exploited to improve the blast mitigation capability [13][14][15][16][17][18][19][20][21][22]. The deformation and failure of sandwich structures subjected to underwater impulsive loads is complicated due to competing damage mechanisms, complex failure modes, interfacial effects and material heterogeneity.…”

Damage and deformation in composite sandwich panels exposed to multiple and single explosive blasts

“…(kPa) (kPa ms) (kPa ms) (mm) Study c relates to the effect of core thickness and is partially presented in previous publications[20,48].b Additional data from other core thicknesses and blast conditions included for the discussion.c Data acquisition failed during test.d Measured peak shock pressure and impulse is equivalent to the gauge measurement or overpressure.…”