ABSTRACT
The effects of stress concentrations on the mode of failure and energy absorption characteristics of thin-walled prismatic composite tubular sections under axial loading are considered. A wide range of parameters were investigated in an experimental programme of over 300 test samples. The composite material was continuous filament random E-glass reinforcement in an orthophthalic polyester matrix at a fibre volume fraction of 23%. Specimen geometry effects were considered by testing square and circular tubular sections of different widths/diameters and wall thicknesses. The stress concentration considered was a circular hole, and a range of hole sizes were tested. The effects of the position of the stress concentration were documented for the square tubes by varying the proximity of the hole to the corner. The effect of interacting stress concentrations was considered by placing two smaller holes in close proximity. Loading rate effects were included by testing at quasi-static rates and at impact rates of 5ms-1. Data are presented for 58 permutations. The specific energy absorption (SEA) was shown to decrease with increased loading rate. Below a certain threshold size of stress concentration there was no effect on SEA. Above this size unstable failure occurred due to crack formation, triggered at the stress concentration and a large reduction in SEA was observed. The drop in SEA was more marked in the quasi-statically tested samples than the dynamically tested samples, which exhibited greater tolerance to the inclusion of stress concentrations.
