Energy absorbing characteristics of aluminium beams strengthened with CFRP subjected to transverse blast load

Carbon fibre-reinforced polymer (CFRP) strengthening of structures has been gaining increasing interest, traditionally applied to concrete structures, and more recently applied to metal structures. Epoxy bonding of carbon fibre to metal has been successfully employed for strengthening structures loaded under static and impact loads. In this paper the metal-fibre bond is investigated under impulsive loads by the application of explosives to fully clamped solid aluminium beams. It is shown that the use of bonded CFRP to metal structures that undergo large plastic deformations is advantageous, since the full strength of the carbon fibres is utilised as a result of the large strain field produced by the plastic deformation in the metal. The experimental results show that a significant amount of energy may be absorbed by the layer of carbon fibres bonded directly to the metal, however subsequent carbon fibre layers suffer from interlaminar debonding mechanisms as a result of shock spalling that reduce their efficiency. A theoretical method is developed whereby the energy absorbed by the carbon fibres may be determined, and the remaining explosive energy is absorbed by the plastic deformation of the metal. Fibre efficiency factors for multiple fibre layers and dynamic effects are introduced and are shown to produce reasonable agreement with the test results.