Effect of impactor radius on low-velocity impact damage of glass/epoxy composites

With composites finding increased use as primary structures in commercial aircraft, it is necessary to understand the development of damage when a laminate is subject to low-velocity impacts from a variety of sources, which often occur during normal service operations and routine maintenance. In particular, contact with ground service equipment can present a blunt impact to the composite structure. Therefore, the effects of bluntness of an impactor are of interest as this is related to the development of any internal damage in the laminate, or even the surrounding structure, and also affects the visual detectability of an impact event. The objective of this investigation is to determine the effect of impactor radius on the impact damage resistance of composite panels. A low-velocity pendulum impactor was used to strike 200 ¢ mm2 woven glass/epoxy composite plates of 3.18 and 6.35 ¢ mm thickness. Hemispherical steel impactor tips of radius 12.7, 50.8, and 152.4 ¢ mm were mounted to a piezoelectric force sensor which measures the contacting force history during the impact event. Distinct threshold energy levels defining the onset of delamination and backside fiber breakage have been measured to increase significantly with increasing impactor tip radius due to development of higher contact area.