Effects of different widths of CFRP plate strengthened aluminium tubular sections subjected to two-flange-loading conditions

Abstract

This paper presents a test program on strengthening of high strength aluminium tubular structural members using externally adhesive bonded carbon fibre-reinforced polymer (CFRP). A series of tests was performed on carbon fibre-reinforced polymer strengthening of aluminium tubular structural members subjected to End-Two-Flange (ETF) and Interior-Two-Flange (ITF) loading conditions. A total of 20 web crippling tests was conducted. The investigation was mainly focused on the effects of different widths of CFRP plate strengthening against web crippling. Three different widths of CFRP plate strengthening were considered. The test specimens were fabricated by extrusion from 6061-T6 heat-treated aluminium alloys. The tests were performed on three different sizes of square and rectangular hollow sections which covered a wide range of web slenderness (flat portion of web depth-to-thickness) ratio from 6.2 to 62.8. Most of the strengthened specimens were failed by debonding of CFRP plates from the aluminium tubes. There are mainly three different failure modes observed in the tests, namely the adhesion, combination of adhesion and cohesion, and combination of adhesion and interlaminar failure of CFRP plate. The failure loads, failure modes and the load-web deformation behaviour of the aluminium sections are presented in this study. The web crippling capacity of aluminium tubular sections are significantly increased due to CFRP strengthening, especially for those sections with large value of web slenderness ratio. It is found that CFRP strengthening against web crippling to be effective when the CFRP width having the same width as the bearing length.