The Effect of Processing on the Underwater Explosion Shock Behaviour of GRP Laminates

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Abstract
This paper compares the impulse (shock) loading response of glass reinforced polymer (GRP) laminates fabricated by the wet hand lay-up and resin transfer moulding (RTM) techniques. The GRP prepared by the hand lay-up technique contained a large number of microstructural defects whereas the GRP fabricated by RTM was almost free of defects. The laminates were tested in a small scale underwater shock facility where they were exposed to increasing levels of shock loading produced by an underwater explosion. Regardless of the fabrication technique, the laminates developed some cracks in the polymer matrix and small delaminations along the polymer/glass fibre interfaces when tested under low shock loading conditions. The damage was caused by the deflection of the laminate under the pressure of the shock wave. Under high shock loading both laminates experienced more severe damage in the form of wide cracks in the polymer, large delaminations, and broken glass fibres, and this resulted in a significant reduction in the tensile and compressive strengths of the GRPs. However, the intensity of the shock wave needed to be significantly higher for the RTM laminate to suffer the same amount of damage as the hand lay-up laminate, proving that RTM produces a more shock resistant GRP laminate.