Analysis of low-velocity impact damage in reinforced carbon fiber composites by HTS-SQUID magnetometers

Composite materials are susceptible to damage which can be induced by service loads and accidental impacts. The detection of any signature produced by damage is critical to maintaining the integrity of aircraft parts during routine maintenance. A high critical temperature SQUID magnetometer has been successfully employed in the evaluation of the behavior of multi-ply carbon fibers reinforced composite panels for aeronautical applications under low-velocity impacts. Measurements of the induced magnetic field have been carried out above specimen damaged with energy impact from 1 to 40 J. A quasi-linear behavior in two different regimes between the SQUID's response and the energy of the impact has been found. This suggests a correspondence to the detection of intrinsically different damage that occurs in the laminates at different energies.