Carbon-fibre-reinforced plastic (CFRP) strengthening of aluminium extrusions

The flexural behaviour of compound beams in which unidirectional carbon-fibre-reinforced plastic (CFRP) is externally bonded to extruded aluminium box-sections, is discussed. Simple transformed-section analysis and elastic buckling theory have been adapted to predict improvements in stiffness and strength with single-layer reinforcement. Close correlation between theory and experiment is observed and maximum gains in stiffness and ultimate strengths of 75% and 63%, respectively, are demonstrated with only a 7% weight increase. It is shown that the effects of the adhesive can be neglected when predicting the performance of the hybrid beam. Shape optimisation has been successfully applied to illustrate the potential of this technique for 'new-build' applications. Initial findings have produced weight savings of 33% in comparison to an all-aluminium optimised box-section. (C) 1997 Elsevier Science Ltd.