Experiments and crushing mechanism analysis of hybrid square metal tubes with filament wound CFRP

Abstract

Hybrid tubular members consisting of a metal tube externally reinforced with carbon fibre have been shown to be efficient energy absorbers. Several studies have used filament winding techniques to fabricate hybrid tubes, principally with circular cross-sections. Filament winding allows for a wide range of discrete fibre orientations. The present study develops an analytical technique to predict the mean crushing force of hybrid square tubes with arbitrary metal tube material and arbitrary carbon fibre orientations. Initially, an experimental study of the quasi-static axial crushing of 40 hybrid square tubes with a variety of metals (steel, aluminium and stainless steel), and a variety of filament winding angles (45°, 67° and 90°) and plies, is described. Comparisons of filament wound tubes are made with previous studies by the author and co-workers of nominally identical hybrid tubes fabricated with the hand-layup method. Previous crushing mechanism theories of bonded metal-fibre square tubes are extended to consider the different metals and fibre orientations. Based on the observations in the experimental program, a new theory is developed for the case where the metal and fibre become unbonded, and is shown to compare well with the experimental data. The analytical model indicates that when the carbon fibre remains bonded to the metal throughout the crushing process, the mean crush load is on average 54% higher than when the fibre becomes unbonded. This indicates the importance of the metal-fibre bond for optimum performance of hybrid tubes.

Keywords

• Hybrid tubes
• Carbon fibre
• Axial crushing
• Mechanism analysis
• Filament winding