Residual torsional strength after impact of CFRP tubes

This paper investigates the residual torsional strength of cylindrical T300-carbon/epoxy tubular specimens damaged by low-velocity impacts. A total of 24 specimens were subjected to a 7 J transverse impact under various torsional preloads. First, the torsional strength of four different lamination sequences is studied. Later it is compared with the residual torsional strength (RTS) of tubes impacted under different torsional preloads. FEM models were developed to investigate the effect of the impact-induced delaminations on the torsion-after-impact strength. The Acoustic Emission (AE) technique was used to study the damage propagation during the torsional loading. Results show that, even if the absorbed energy during impacts is the same, the residual torsional strength of the laminates is highly affected by the torsional preload.